Emma and Nate explore spring vegetable gardening so you can take full advantage of the cool months before last frost.

Peas growing in a garden

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Show Notes

Some of our favorite vegetables can not only be grown before last frost, but thrive in the cool months before we can grow tomatoes and other classic warm season crops. With our region’s short growing season, moving up your planting window is a welcome opportunity for antsy gardeners after a long winter. In this episode of Granite State Gardening, UNH Extension’s Emma Erler and Nate Bernitz share proven tips and solutions for successfully growing cool season veggies. After listening, or even while you’re listening, head out to the garden and get growing. With a few tricks, you’ll be amazed how much you can grow and harvest before the heat of summer.

Featured Question: Row Cover Frames

Featured Plant: Garlic (Allium sativum)

Gardening Tip: Harvesting Cool Season Vegetables

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Nate Bernitz  00:00

Welcome to the Granite State gardening podcast from UNH Cooperative Extension. On today's show, we're talking about growing cool season veggies. Whether you already have spinach and peas in the ground, have broccoli started indoors or aren't even sure what cool season veggies are. We're glad you're listening. In the shownotes you'll find several helpful resources, including our chart on when to plant and transplant. You'll also find details on our upcoming Facebook Live talk on school season veggies, which we've scheduled for April 19 at six o'clock, where you can ask questions and get answers live from Becky Sideman, who you know from episodes four and five. nine episodes and we're thrilled that Granite State gardening is apparently already a top 50 gardening podcast out of more than 2000 gardening podcasts on iTunes. As we continue to produce podcasts and grow to connect with more gardeners, we welcome your feedback topic suggestions and gardening questions by email at GSG dot pod@unh.edu. We're also on Facebook and Instagram at ask UNH extension where we post regular tips and resources. Okay, let's dig into cool season veggies. Greetings Granite State gardeners. I'm Nate Bernitz joined as always by horticulturist and UNH extension field specialist Emma Erler. Today, we're talking about a very timely topic crops that will tolerate some cold, we're calling these cool season veggies. And I know this is on your mind, everyone. We're all itching to get into the garden, we want to plant as soon as possible. Some of us may plant a little too early. But hopefully after this conversation, you'll be prepared to succeed planting cool season vegetables in your garden. So Emma, let's get started by just digging into essentially which crops we're talking about which of these vegetables will tolerate colds? And what exactly does that mean? How cold will they tolerate?


Emma E  02:18

When we're talking cool season crops, we're talking plants that actually adapted to cool climates. So vegetable plants that are happiest when the temperature is, let's say below 70 degrees Fahrenheit. So these are not the plants that are thriving in mid summer. These are the ones that like the cooler spring that we have or maybe even the fall. So or talking about things like the brassicas, which we're familiar as being cabbage, kale, collards, broccoli, Brussel, sprouts, kohlrabi. Actually interestingly, all of those plants are the same species. brassica, oleracea, which is kind of cool. This is plant breeding at work, where we have all of these different cold crops, all these very different looking things that are the same species. But some of our some of our root crops fit into this group to radishes, turnips, onions, and leeks. A lot of times we're having leek soup in the first part of the season or maybe later on. And spinach, peas, lettuce fit in as well. And there's some other crops that like just a little bit warmer, where there's less of a chance of frost. And that's going to be things like beets, Swiss chard, mustard greens, and maybe even carrots and parsnips.


Nate Bernitz  03:38

And so you've been talking number one about air temperature, and we should probably talk about soil temperature too. But our crops either cool season or warm season, are there any veggies that just do well, no matter what the temperature is? Or are you really talking about some vegetables that do well when it's cool, and then do poorly when it's warm, or vice versa?


Emma E  04:00

Yeah, so I'm talking about some that that do poorly when it gets really warm. Some that you can grow during the heat of the summer, if you're growing a specific variety that's been bred for that, but they're really not going to be quite as happy. And there are many others too. So some of your more tender vegetables, let's say a tomato or a cucumber that that won't tolerate really any cold at all, or at least they'll grow very poorly. They're not going to take a frost. So with a lot of our cool season crops they are their growth is typically going to actually speed up when we get into warmer temperatures or really hot weather. And what happens is a phenomena called bolting, which basically means the plant produces a flower stock and seeds. And at that point, whether it's leaves, stems or root, perhaps we're talking about, let's say a radish. That vegetable material actually becomes to woody or bitter for us to really enjoy or in the case of radishes, far too spicy. So these plants are going to have a much slower growth, they're not going to bloom when we have cooler temperatures, and you're going to get a much better higher quality resulting vegetable versus let's say your tomato, that's not going to do anything when it's really cool, cold, and the growth is going to really explode once we get into the heat of the summer.


Nate Bernitz  05:31

Okay, so it's really important to know for any particular vegetable you're growing, what are its ideal growing conditions, and what will it tolerate on either end, going back to soil temperature, though, thinking this is especially important when we're talking about certain vegetables that we're not starting indoors, but rather, are planting directly into the garden. So tell me about some of those cool seeds and veggies that we're planting directly in the garden. And what's the coolest they will tolerate? Right, so the coolest the soil will be or maybe coolest, the air temperature will be to where they're actually going to germinate and start growing for you.


Emma E  06:09

you can actually start pretty much any cool season veggie directly in the garden with some crops that have a take longer to develop, let's say brussel sprouts, for example, that take about 100 days to go from seed to harvest. Usually people do like to start these indoors so that you have a more mature plant and you're getting a harvest sooner, perhaps you're even going to get a harvest before the true heat of the summer comes that would work for say broccoli to. Most people are probably going to be looking at directly sowing some of their greens. So something let's say like spinach or lettuce, peas typically get directly sown in the garden soil, because they don't transplant terribly well. And most root crops too. So you can you can transplant carrots or beets. But I've never had terribly good success with that I find it's much easier just to sow those seeds directly in the garden, kind of the one exception I can think of is onions, those can take a long time to develop. So it's it's useful to start those indoors. In terms of when you can do that though temperature of the soil is important. And I think we've mentioned this before, but having a soil thermometer is going to be key here so that you know when the soil is going to is warm enough that plants are going to germinate at a high rate. And so for the most cold tolerant crops, let's say those brassicas, you're looking at the soil needing to be at least 40 to 45 degrees. If you're just kind of looking for maybe the safest baseline for everybody that falls into the the cool season crop category, I'd say wait for the soil to get up to at least 50 degrees, then once it gets up into the 60s, then you're really going to start getting a higher germination rate and faster germination. When you do sow seeds when the soil is very cool, let's say 45-50 degrees, the plants take longer to come up. And they're going to grow a little bit more slowly too.


Nate Bernitz  08:21

Of all these cool season veggies, my understanding is that spinach is the one that will tolerate the coolest temperatures and still get growing Is that your understanding too, and being the crop that you can plant first, right? A lot of people are planting in groups because we only have so much time and when you're gonna be out in the garden you want to do as much planting as possible. But if you are really getting it down to a science and planting each individual crop as early as you possibly can, it's spinach, right?


Emma E  08:49

spinach is super, super tough. Those plants that are some of those those brassicas too, though will also take really cool really cool cold temperatures. So your your kale, your collards, your broccoli, those can go in really early. If you really want to get a jump on the season, though, you will start those indoors from seed and then have transplants that you're putting outside. Once that soil temp is is at least up to 40 degrees.


Nate Bernitz  09:17

Yeah, and so on, let's say April 1, generally speaking, where would you expect soil temperatures to be?


Emma E  09:25

Oh, gosh, good question. April 1, I would think that the temperature might depending on where you are in the state might be starting to creep into the low 40s you know, once the snow is gone, and once the soil has totally dried out and thawed, it does warm up pretty quickly if we're getting a lot of bright sunny days. So I would say for most people are probably looking at planting let's say mid April or so. But he might be in the low 40s by April 1 or you know I actually haven't stuck a soil probe in The in the ground near me where I live in Southern New Hampshire. But I would guess that it's it's getting close to that because the ground is totally thawed, we're actually past mud season in my backyard. So I would guess that we're getting, we're probably close to that mark, if we're not there already.


Nate Bernitz  10:17

just to be transparent. We're recording this on March 24. So we're not releasing this for a few days. But I want to get into some of these kind of confusing terms, at least confusing to me. One of them is many of these veggies come with instructions to sow or to transplant as soon as the soil can be worked, I'm sure you've seen that phrase, too. And it's not clear to me exactly what that means. How would you kind of go about defining that? And do you have a different way of framing when you can transplant these out?


Emma E  10:54

Yeah, that is kind of it's kind of a confusing term, right? That's not typically defined, when the soil can be worked. Basically, that means that it is completely thawed, and it has dried out. So right after the snow melts, this is what I mentioned mud season before, the soil is still very wet. If you were to walk across it, you're going to be leaving big deep ruts. And if you're going to try to work it at all, you're going to typically form big clumps, or clods. So it's really important not to be trying to cultivate or till the soil, when it's still in this, this wet soggy state, right after the snow has disappeared. So you can actually end up damaging soil structure when you do this, it gets very clumped together, you could also be compacting it. And when it's in that state, it's really not going to be ideal for any sort of plant to thrive either. So when we're talking about putting vegetables in the soil, cold and wet, those are kind of recipes for rot. So some people might have issues with damping off, which is a fungal disease issue that happens in exactly those conditions that can happen outside in the garden. It can also happen when your seeds starting indoors when you have cool wet conditions. So you want that soil to be nice and dry. Think of what the soil you know how garden soil would feel. If you're if you're working, if you're digging it up. And later in the summertime, when it is dry when it when it you know has a bit of moisture, but it's not. It's not soggy squishy.


Nate Bernitz  12:33

But at least in southern Central New Hampshire, the soil can be worked in early to mid April. fair to say right?


Emma E  12:41

Yeah I mean, it depends on the season, we didn't get a whole lot of snow this particular year. So people are going to be able to work the soil a little bit easier. Because you where I live anyways, the snows already gone. If you're probably more in the the central part of the state or the northern part of the state, you're gonna have to wait quite a while longer. So there is some variability from year to year. And you do just kind of have to pay attention to what's going on with the weather, the more you're trying to push the season. You know, of course, the more likely you are to run into issues with weather.


Nate Bernitz  13:13

And so the other limiting factors, at least for the warm season crops is when that last frost is going to be in the same way that the idea of the soil being worked as a little bit subjective and hard to exactly predict when that's going to be of course, we're also guessing on when the last frost is going to be. But the good news with these cool season veggies is they can all, to some extent or another, tolerate either light frost or potentially even colder temperatures than that. And the other thing is that we can have really unseasonably warm weather and then very cold weather and the soil temperature is not responding in that same way. The fact that it might be 70 degrees one day, and 25 degrees the next night, the soil temperature is not on that same roller coaster. So we have to remember that those two things are distinct and as long as a veggie can tolerate colder temperatures, we really want to be locked more into the steady progression upwards that soil temperature. What would you add to that?


Emma E  14:18

Oh I think you nailed it. Yeah, soil temperature definitely does not fluctuate as much as air temperature. So you can't base your planting entirely around air temperature. In March already this year, we've had some days where we were pushing 70 degrees, but there's still snow on the ground right and there's still ice so the soil temperature was not appropriate for planting despite the you know, very spring like temperatures. And the same goes once you've once you've planted in the ground too. So once that soil is let's say heated up to 50, 55 degrees, even if we have a day that say it doesn't get above 36. The soil temperature is is not going to You know, reflect the air temperature it takes a while for the soil to warm up and takes it a while to cool down in the fall.


Nate Bernitz  15:06

So one thing that I've noticed in shopping my seed catalog and figuring out which varieties I was going to select is that some of these cool season veggies I think are bred to be more cold tolerant, and some are bred to be a little bit more heat tolerant. Right. So how do you think about variety selection when it comes to your cool season veggies,


Emma E  15:28

I think I'm usually more concerned with the heat tolerance when I'm talking about a lot of these cool season crops. These are crops that, like I said before, are adapted to cooler climates. So I'm more concerned about what the quality of that plant is going to be if it gets really hot, you know, are they going to be resistant to bolting? Are they going to keep, let's say a better flavor for longer lettuce is a great example. Because lettuce can get really bitter when it gets hot. So a slow bolting variety is great there. Same with radishes. If you've ever you know eaten a radish that was grown in the summer, or picked once it got really, really hot out really, really spicy and tough versus those cooler season harvested roots that are that are much more mild. So I am often looking for heat tolerance, on on everything from I said radishes to lettuces to broccoli, where I want plants that are going to be okay into the summer. But there's there's gonna be some that are perhaps a little bit more cold tolerant too. But like I said, I'm more concerned about the heat tolerance.


Nate Bernitz  16:44

And maybe we're choosing varieties that are a little bit more heat tolerant. But still, we've got a fairly short window to get these cool season veggies growing and harvested before the weather just gets too warm for them to thrive. So that naturally leads to two questions. One, how can you move your planting window up? So you can extend that period A little bit more on the front end? And then the other question, how can you keep cool season crops going a little bit longer? So let's start with how to move your planting window up? What are some techniques to consider for being able to maybe plant in early April instead of mid April, for example?


Emma E  17:26

Great question. I know for a fact that you are actually trying one of these techniques, Nate that that is actually tarping the soil. So you're going to be putting a dark colored plastic like a or a tarp on that soil to actually help heat it up faster using the sun's radiation. So that can help you plant a bit earlier a bit more advanced for the average homeowner perhaps or maybe something that you haven't really been thinking of but having a plastic mulch over the soil is or a you know plastic tarp plastic film, that's going to heat up the soil faster. An organic mulch on the garden is actually going to keep the soil cooler for longer. So if for some reason you had a whole bunch of straw or leaves on your garden, those are going to be insulating the soil and keeping it cooler longer into the season. So if you had something like that on your garden beds, you might want to rake that off to get the soil to warm up faster. Something else that you know, I guess maybe the more advanced gardener might have on their property is a cold frame or two. And these are actually structures that you build right into the soil. A lot of times we will linr them with with cinder blocks or or pressure treated boards and you're basically making a box that set into the soil that has a glass cover or lid. And in these cold frames, you can be starting seeds, you can be growing plants that you know needle a little bit more warmth, or you can be hardening things off that you started indoors before you put them into your gardens. So cold frames are worth consideration. And then row covers to can be used. So a row cover is a typically a spunbonded plastic based material that goes if it's going to be a more permanent fixture over a wire frame. And you're putting these over your crops when you expect that you're going to get a really cold night where temperature is going to be below freezing, or you expect a hard frost. So that's the warm from the soil is going to keep when you have this cold frame going completely over the plant going down to the soil, it's going to keep the air temperature in there from get dropping below freezing ideally, so the crops are fine.


Nate Bernitz  19:49

What's nice about row cover in theory and this, this requires having a little bit of an inventory on hand. But if you have that frame setup, you can potentially change The thickness of the fabric that you're using, at any given time, you can just do a change out. So maybe you're using fabric to warm up an area early in the season but then you're maybe using a lighter fabric or shade cloth even later into the season to have the opposite effect.


Emma E  20:21

Absolutely. And that you just mentioned the the best thing that you can do to keep your cold season or cool season veggies going longer, and that's shading them so that you are keeping the local temperature on those plants a little bit cooler. So people will use shade clubs or they'll strategically plant those crops so that they're they're closer to a fence or something where they're going to be getting afternoon shade, so they're going to be protected from the heat of the day.


Nate Bernitz  20:46

Today, today's featured question is how do I establish row cover and a frame to support it? Before using row cover mulch should be applied around your transplants to suppress weeds and retain moisture. Drip irrigation or soaker hoses are ideal choices for irrigating crops under row cover. If your cover is supported by a frame, you'll have to peel it back to water. So drip irrigation or soaker hoses offer a far less labor intensive and more efficient way of watering your garden. supporting your row cover with frames allows you to keep your row cover on plants longer and can likewise support other fabrics. Consider using either a low tunnel design or an A frame both of which can be designed using either pvc piping, wood or flexible wire such as electric fence wire or nine gauge wire. rebar is helpful for supporting low tunnels although not necessary for a simple wire based design. Whereas you might use fence posts to support an A frame. You can purchase these materials pre fabricated from garden supply stores, or as raw materials from local suppliers. If you're creating frames for individual rows, plan for frame pieces to be spaced every four feet or so along the row, and target hoops approximately 16 to 20 inches high. For a four foot row wire pieces should be about six feet in length. at the ends of your rows consider using double layered hoop pieces if you're using wire. Because the row cover exerts the most pressure on the ends, it's helpful to be able to easily vent your row cover on warm days in the spring. So consider how you might peel back the sides. While peeling back the sides and venting your row cover allows pests in, it may be necessary on a specially warm days without going through the hassle of completely removing the cover. Okay, that's your featured question.  Going back to mulch, you're talking about how a black plastic mulch like I'm using is heating the soil up. But the organic mulches like a straw are going to cool it down. So as we get into the later part of the the spring, you do want to be using that organic mulch to keep the soil nice and cool and to keep moisture in. So depending on how enterprising you are, depending on how much time you want to spend out there switching things out, you can extend the season on either end just by using the right materials at the right time for the right effect.


Emma E  23:30

Exactly. Yeah, for most of the cool season crops, I probably wouldn't be planting them into a black plastic mulch. Although I would be using that with maybe some of my my tender warm season crops. So say I'm trying to grow melons, or squashes that do like a really, really warm soil and really thrive in heat, black plastic is perfect for those. But for the everybody else that I'm trying to keep cooler and organic mulches probably going to be my choice.


Nate Bernitz  23:58

Yeah, that's a good point. So in terms of what I'm doing, like you said, I am tarping the area with somewhat thick black plastic. But yeah, I intend to take that off and neatly roll it up. When I'm actually ready to plant, I can bring that out to us in the future. It's not disposable if you take care of it properly. And I will transplant out what I'm starting indoors and surround it with a nice organic mulch where it does exactly that the same reason why black plastic is helpful for warming up the soil is why you wouldn't want to plant into it with your cool seeds veggies. But probably many of you have either seen this or done this yourself cutting holes cutting planting holes in black plastic, turning it from tarp, like I'm using it, into a mulch.


Emma E  24:47

Exactly. Yeah. And that's something you're gonna see more in the the scale of a commercial farm. Although for the backyard home grower, you can certainly get plastic mulches and there's research out there on The best color mulch for the particular crop that you're growing and where you happen to be Gardening in the country. You know what, what region you're in. But I think a lot of homeowners who are probably going to be looking at using more organic mulches rather than using plastics. I say this of course, and there's probably plenty of people out there that are using dark landscape fabrics or plastic mulches for their backyard.


Nate Bernitz  25:29

And we both know that a lot of gardeners aren't using mulch at all. And that's certainly one takeaway we want people to have is you want to use some kind of mulch, you're the choice of material is up to you, whether you maybe are using something like a plastic mulch for growing your peppers to keep the soil warm, or whether you're using organic mulches like straw to keep the soil cool and conserve moisture either way, you want to use something.


Emma E  25:55

Absolutely, it's that's going to help a lot with disease suppression, with an awful lot of diseases that overwinter in the garden soil. So preventing some soil from splashing onto the foliage or stems of your plants is super helpful. Mulch does that. And like you mentioned, Nate, the mulch is going to help conserve soil moisture, which after last year's drought, and actually we're we're starting off the season this year with a still a moisture deficit, doing anything you can to conserve soil moisture is a good thing.


Nate Bernitz  26:29

A couple other techniques that come to mind as far as being able to move your planting window up by warming the soil, one would be potentially growing in raised beds, where the soil is going to warm up a little bit quicker, I think then it might in the ground, and the other would be hilling in your vegetable garden. How do you think about those two techniques potentially?


Emma E  26:52

Yeah, both of those are excellent. I tend to be a bigger fan I guess of the the raised beds than let's say hills, hills are often used for cucurbits. Right. So yeah, pumpkins squashes, where you you make a little mound of soil that you plant these crops in. There's a lot of people that swear by it, I was never the biggest fan just because I felt like it made it a bit harder to water. Those crops. But raise beds are enormously popular for the backyard grower, especially for a lot of people who don't have a tremendous garden soil so they can bring in some good quality loam and compost to put in a raised bed, the raised bed soil is going to heat up faster. And it's also not going to have the compaction issues that a garden in ground bed would have because you really shouldn't ever be stepping on the soil in our raised bed. So you'll be able to plant sooner typically in those.


Nate Bernitz  27:51

Are any of the cool season veggies really taking up a lot of space. And on the inverse, which of these cool season veggies do you think are really well suited for growing in containers?


Emma E  28:02

some of the brassicas are going to be taking up a fair amount of space. So brussel sprouts, I mentioned those before, but they're going to take pretty much the entire summer to grow before they're ready to harvest. And that's a good size plant. Whether you've ever grown brussel sprouts before or not, you might know that. broccoli and cauliflower, those are also pretty decent size plants, cabbages less so. But they're they're taking up a fair amount of space. So if you have just a small raised bed setup, you're probably not going to get away with growing more than just a couple of these plants. But some of the others really aren't taking up much room at all. So onions can be grown really close together, a lot of the root crops aren't taking up too much room. Same with greens. And with greens, at least you can get multiple harvests in throughout the course of the season. So you might have, you know, potentially depending on what it is, and at what stage you're harvesting, let's say lettuces or spinach, you could have a couple of harvests before the heat of the summer. And then you could be planting again in the fall. Or in some cases, you could be growing lettuces year round too, just knowing that they're often not going to be quite as high quality when you're growing them in the heat of the summer. But there is there is going to be you know, some turnover there. In terms of you know, planting in containers. Pretty much anything can be grown in a container as long as you have a big enough container. I probably wouldn't bother trying to grow let's say a broccoli plant and a container or brussel sprouts. But something that I can harvest from throughout the season would perhaps be more appropriate. So let's say like swiss chard where I can just break off leaves here and there, same with kale, or some of the root crops might be easy enough to harvest if you're growing in a container. So carrots or beets or something Like that really, really easy to grow in a container. And greens, of course, a lot of people grow salad greens in containers, window boxes, whatever they have.


Nate Bernitz  30:11

Yeah, I certainly have. And I really enjoy that and recommend it. But you've brought up spacing. So of course, any seed packet or transplant you're getting, there's a label that says recommended spacing. But in your view, kind of going beyond just the recommended spacing are there some of these cool season veggies that lend themselves well to maybe pushing the envelope and growing and with more density strategy in mind, like square foot gardening and these other kind of philosophies about dense planting?


Emma E  30:45

Yeah, with the greens. So let's say lettuces, spinach, you can get away with planting these pretty close together, particularly if you intend to harvest before they get full size. So let's say you want to grow baby baby lettuce greens, then you can plant really pretty close. Or if you do want to grow more mature plants, you could be thinning out some of these plants as you go to have those baby greens in your salad, the ones that you need to call so there's enough room for the mature plants. And then you know, you're getting a little bit as you go. Some of the root crops too can be grown pretty darn close together. radishes really don't need to be spaced all that far apart. And just a couple of inches. Same goes for carrots. So you can get an awful lot of produce in a very small space.


Nate Bernitz  31:35

And radish and carrots actually are nicely grown together.


Emma E  31:40

They can be Yeah, yeah. And they're there in different plant families. So we're not too concerned about sharing pests or diseases there either. So on if you're looking at maybe rotating crops, where you grew your radishes last year is is also a perfect place to put your carrots this year.


Nate Bernitz  32:00

I guess my thinking is that radishes grow much quicker. And so they're going to be able to help you suppress weeds, which is such an issue with carrots. So you could potentially be getting that radish harvest as your carrots are developing. So maybe inter spacing those that'd be a good strategy.


Emma E  32:17

Yeah, fair point, are having a couple of rows that are pretty close together. Yeah, because a lot of the radishes, we're talking about a harvests in just 20 to 30 days. Whereas carrots are probably you're probably looking at more like 50, 60, 75 days or so. So they'll be there'll be with you a little bit longer in the garden.


Nate Bernitz  32:40

Do you have any similar thoughts about growing leafy greens, what what you might plant those either within or, or very close to where there's going to be maybe some synergy,


Emma E  32:52

I would probably be thinking about planting saw my my leafy greens near where some of my warm season crops are gonna go. So let's say that the lettuces or the or the spinach is being grown in the area where I'm going to be putting my tomatoes in. And so those those crops are perhaps going to be ready for harvest or shortly ready for harvest, right as those, those heat loving crops are going into the garden. So you're really not losing space in the garden here, as soon as one is is harvested, then you're filling in that space with something else.


Nate Bernitz  33:28

Right, that makes sense to consider in your garden plan. And I really like that, that's that's how I'm going to approach it this year for sure. Something that's vexing to me is fertilization when it comes to the fact that you're not planting everything at the same time. And you're potentially planting in these interspersed ways. So maybe you have your soil test results. And it calls for certain number of pounds of particular product per 100 or per 1000 square feet, except that you're not applying all that fertilizer at the same time. Right, you have to apply it shortly before you're actually planting your crops. So I guess how do you wrap your head around that? And how do you actually turn theory into practice as far as using your soil test results to apply fertilizer when and where you need it.


Emma E  34:16

When I am thinking about using fertilizer in the vegetable garden, I'm often leaning more towards organic fertilizers. And a lot of these are slow early sources of nutrients meaning though they have to be broken down by microorganisms in the soil in order for those nutrients to be converted into a form that a plant can actually use. So it's not like I'm instantly feeding the garden. If you're looking at amending all of your garden soil and you intend to have that whole area planted out and you're actually going to be tilling then I would probably be thinking out fertilizing that whole area with my slow release fertilizer to start with when I'm incorporating nutrients. If you let's say just you're going to be using one half of the garden for your cool season crops and you're not going to be putting your warm season crops until later, then I might just put that fertilizer down and the half that I'm going to be planting right away. And then later on incorporating the fertilizer, let's say a month, six weeks later, and the other area where I'm gonna have my warm season crops, but it's definitely easier to incorporate that fertilizer into the soil right before you plant as opposed to trying to side dress everything, meaning you plant your crop, and then you try to fertilize it. Although if you get your soil tested and get your soil test results, that's something that's going to be recommended. So you're going to have your fertilizer, your your first dose of fertilizer that goes down, typically right before your planting. And then in many cases, you're going to come back at, let's say, a month or so after planting and side dress. So putting a little bit more fertilizer down either in a ring around that plant or in a line along that plants that you have a little bit more to push you, you know through the rest of the growing season.


Nate Bernitz  36:10

Yeah, so with leafy greens, you're talking about side dressing in a line, right?


Emma E  36:14



Nate Bernitz  36:15

So I guess what you're saying is an argument kind of against the the idea of intercropping. Right? Like, do you actually want to plant your leafy greens right next to maybe your one of your warm season crops? Not because they don't do well together? But because it makes fertilization a real challenge?


Emma E  36:36

It could? Yeah, it definitely could, I think sometimes it's actually easier to rather than trying to interplant all these things just to have a plan for what you're going to replant when that crop is gone. So where you're putting all your radishes, for example, once you get into the heat of the summer, it's no longer they're no longer going to be growing very well unless you have a super heat tolerant variety. So I might be looking at putting something like bush beans in to that space instead.


Nate Bernitz  37:04

That brings up a really good point, because a lot of these cool season veggies Yeah, they're gonna not be at their peak quality as we get into the heat. But that's typically going to be after, you might want to actually plant a lot of your warm season crops like you're not going to be pulling a lot of these cool season veggies Memorial Day weekend, they're going to go a little bit longer than that. So you end up planting a lot of your warm season veggies and you're still left with the question. Okay, what do I do in this area where I had cool season crops, maybe I'm going to plant cool season veggies there in late summer for a fall harvest. But what do I do with that area in the middle of the summer?


Emma E  37:47

Yeah, definitely a big question there. So that the number one crop, I guess that comes to mind for me is the wish beans, because those can be planted multiple times throughout the season. And they they do quite well in the heat. So beans can definitely go into some of those spots. Not even if you have a row being someplace else you could put beans in, let's say where where all of your spinach was or where your radishes were. Some people do just keep successfully seeding some of those cool season crops too, and are harvesting at at I guess, more frequent intervals. So you can you can still grow radishes you can still grow lettuces throughout the summer. But they're not going to be there's going to be a quicker turnover because you're not going to be a leave those crops in the soil for a really really long time and still have them you know turn out to be really good quality.


Nate Bernitz  38:41

Another thought I have is for some of these crops that take up a lot of space. You might plan for those crops to grow into an area that was supporting cool season veggies in the spring. Right You might plant zucchini, squash, something cucumber, something like that, that you're planning on trailing next to your cool season area as as they grow. It might be the perfect time for those cool season veggies to come out to accommodate those vining plants as they grow. Another option that might be more on the small farm scale, as opposed to the garden scale would be thinking about summer cover crops.


Emma E  39:27

Yeah, those are those are both really good points and you know cover cover crops, like you said are often used more farm scale but you can definitely buy them in quantities that are appropriate for the backyard garden to a lot of the seed companies are selling smaller quantities of cover crop seed because home gardeners are getting interested in in using those.


Nate Bernitz  39:49

For me the barrier to a summer cover crop is you want to terminate it so that you can to have it so you can have a fall harvest of something And I don't really want to deal with the hassle of trying to terminate a cover crop. So I'd rather be planting a cover crop in late summer. And the frost and cold of winter does the termination for me. But especially on a small farm scale where you do have the equipment, you can grow a cover crop for a certain period of time terminated, and then get right into your next planting.


Emma E  40:24

And by terminate, of course, you mean tilling that material in.


Nate Bernitz  40:28

right, yeah, especially that garden small farm scale where, where you're not going to be using different techniques for termination. But anyway, some different some different options. We'd love to hear from listeners to on how you think about this. What are you planning for your cool season veggies and that transition into summer, we'd love to share some of your ideas with other listeners. So let us know. as we get into June, in particular, pest and disease issues start to crop up. So we get a couple bonus months, April, May, we're probably not dealing with too many issues. But as we get some of those later harvests, we're starting to face some foes that I bet many gardeners who are listening are all too familiar with. So I was thinking we'd talk about those in groups. So let's start with the brassicas. What insects and diseases are you particularly concerned about? And what strategies would you consider for managing them?


Emma E  41:32

Well, I guess we'll start off with the insect pests. So there are three different cabbage moths that will feed on these crops. So you've got cabbage looper, imported cabbage worm, and the Diamondback moth. All of these are moths that are going to be laying their eggs on susceptible plants, so on your kale and your broccoli, cauliflower, etc. And when those eggs hatch, you're going to get a whole bunch of larvae, caterpillars that are taking big chunks out of those leaves, leaving frass droppings if it's on a, you know, broccoli, they may be eating the buds and you you've just got a mess on your hands. So those are absolutely a concern. aphids can also be a big issue on a lot of the brassicas and their cabbage aphids are they're kind of a darker color. And these are going to be sucking SAP out of plants. So leaving leaves looking distorted, maybe they have some honeydew on them from the excretions from the aphids. And you're also looking at some fungal diseases too, that can affect plants in that that family. So things like black rot, blackleg, alternaria, some of these can be introduced to the garden with infested seed. So if you saved your seed for some reason or didn't get seed from a good source, then you might be bringing disease in that way. But there's, you know, it's the best ways certainly with any sort of disease issue on a brassica crop is going to be to probably cull that plant and then to rotate where you're planting those crops the next season with insect pest crop rotation is not going to help quite as much. But at least with the with the aphids, and certainly with the cabbage worms, using those row covers that we mentioned earlier can be super, super helpful. So having those wire frames set up over your plants and having a lightweight row cover over the top is actually going to exclude these pests from getting to your crop.


Nate Bernitz  43:39

Yeah, row cover is really arguably more helpful for the cool season veggies than the warm season crops because those warm season crops tend to need to be insect pollinated. And the cool season veggies tend to not need to be insect pollinated, at least per my understanding. And that's a real limiting factor for using row cover for warm season veggies because it's excluding insect pests, but excluding pollinators as well. So for your leafy greens, for example, the only time in that row cover needs to come off as when you want to harvest.


Emma E  44:13

Exactly, yeah, couldn't have said it better myself. Make the row covers make a lot of sense, especially for those that don't really want to be using a whole lot of pesticides in their garden to manage these pest issues. So yeah, worth consideration. I mean, there are of course, pesticides you can use to there are some biological and organic pesticides, but the fewer pesticides you can use in the garden, the better and I think a lot of us are going to be happier to have that totally pesticide free crop that came from under a row cover.


Nate Bernitz  44:47

Do you think it's worth mentioning any particular biological pesticides for the brassicas and would you potentially need to use pesticides if you're properly using row cover? Or is it an either or scenario


Emma E  45:01

with the row cover it's going to be more of an either or you shouldn't need to be using pesticides underneath your row cover unless you're looking at maybe using a fungicide. One insecticide that you may end up using with your brassicas is bt, Bacillus thuringiensis. And this actually kills caterpillars, and only caterpillars. So you're only using your bt for things like your your cabbage loopers or your diamond back moth larva, not going to be helpful for aphids. But for those brassica crops, those those caterpillars are often the biggest concern.


Nate Bernitz  45:46

One other organic pesticide option is spinosad. And our colleague Rachel Maccini, who manages our pesticide safety education program, briefly joined us to share a few thoughts on using spinosad products in the garden. For this integrated pest management featured tip.


Rachel Maccini  46:03

spinosad it is considered an organic biorational pesticide registered by both EPA in the state of New Hampshire. It is made from the fermentation of a naturally occurring soil bacterium and it's considered a reduced risk pesticide. What this means is it has shown to be relatively non toxic to people and has few environmental side effects. Why would you consider this product for your cool season crops like brassicas? because this product is considered a reduced risk pesticide and has shown effectiveness against several insects like caterpillars, thrips, and beetles. It is being recommended for pest management. It has gained popularity amongst growers because of its ease of use, variety of formulations available and the fact that it is Omri approved. However, keep in mind it is a pesticide and like other pesticides, it has some degree of toxicity to certain natural enemies and bees. It is important that before applying this product you read and follow the label and refrain from applying when crops are in bloom.


Nate Bernitz  47:08

Thanks, Rachel, I think spinosad is a really great option alongside bt for use with cool season veggies. And really any time of year for a variety of pests in the vegetable garden. And with aphids, a stream of water can help you quite a bit without even needing to use a chemical right?


Emma E  47:29

That's true. Yeah, just knocking them off of the plant sometimes is all you need to do and they won't be able to find their way back up.


Nate Bernitz  47:35

just to kind of highlight the fungicides and fungal disease issue for a second, because I think that this is a source of confusion.


Emma E  47:45

Yeah, so there, there are some fungicides that are actually going to kill the fungus. others that are just going to be preventing its growth or preventing spores from germinating. But regardless, if you have a let's say, a leaf that is heavily infested, you cannot get that fungus to go away. And that leaf is not going to heal itself by using a fungicide. Your real goal is trying to protect any new growth on that plant from getting infected. So typically the fungicides come out when you first see signs of infection on on leaves of the plants when you first start to see leaf spots, let's say powdery mildew, something like that, that that's really the stage before things are too far gone. So it's important to be scouting in your garden all the time. You know, for many of us going out in the vegetable garden every day is not unheard of. So go out and look for signs of some of these diseases. And of course, have it accurately identified, which is definitely something that UNH extension is happy to help you with to make sure that number one, you you know what the issue is. And then number two, if it is appropriate to use a fungicide you're using something that's going to work against that particular disease. And that's going to be labeled for use on the crop that you're growing. So that you're being safe and as environmentally responsible as you possibly can be.


Nate Bernitz  49:13

I know this is true to some extent for insects, but I think it's more true for fungal diseases that it's a bit out of your control whether that infection is going to occur. You can't necessarily shield your your crops from it and we can't control the weather. Can you talk a little bit about how the weather conditions environmental conditions and one spring versus another may impact to what extent disease is a challenge?


Emma E  49:40

Yeah, the weather weather conditions really influence disease. occurrence. Typically, fungus fungi grow best in wet conditions. So extended leaf wetness or extended soil wetness. So having a wet soggy soil for a long time can encourage a lot of root rot issues. So if we have a spring where it's where it's really, you know, cool and rainy, let's say right right through, you know May, which is kind of prime growing time for plants, it's very likely that you're going to have some fungal issues, particularly if you've had those issues in the past. So if some of those spores or that, you know, disease is, is already in the soil in the area, actually a way that a lot of New Hampshire growers or farmers are combating some fungal disease issues is by growing in high tunnels. So they're actually growing their crops under cover, so that they don't have to deal with the leaf wetness from precipitation throughout the season. There of course, other diseases too, if you've ever dealt with powdery mildew. This is a disease that actually does not, the spores do not germinate when the leaves are wet, but they do when you have really high humidity. So if you have a really, really humid, Summer of plants are spaced really closely together, which is increasing humidity, then you tend to have bigger issues with that. But we can't control that we can't obviously can't control the weather, and we're when we're growing outdoors, best thing we can do is just keep a close eye on our crops. And if we have had an issue with a particular disease, we might look into whether we can find a variety that has some resistance to that disease, so that we're hopefully getting a good crop without even really having to worry about any sort of treatment.


Nate Bernitz  51:34

Yeah, that's a great point. So along with considering heat tolerance as something you're really looking for, and variety selection, looking for varieties that are resistant to a particular disease that you've experienced, that you've properly identified, and now you're planning to prevent in the future. Let's talk about leafy greens. I don't think there are quite as many insect pests that are a problem for leafy greens. I know there are some so what are the insects and diseases you're particularly concerned about their and how do you prevent them or manage them.


Emma E  52:10

With leafy greens again, we're definitely looking at aphids, there's there's pretty much an aphid for everything. So we're looking for aphids on those plants. on spinach or swiss chard if you grow those crops or beets to anything that's in that that Chenopodioideae family you can get an insect pest called spinach leaf miner, and this is this insect will actually eat the leaf tissue in between the the lower and upper surface of the leaf in leave these little galleries in the Leafs you'll see these transparent areas throughout the surface of the leaf. less of an issue, let's say on a beat if you weren't intending to eat the beet greens, but if you were hoping to eat this spinach or this obviously eat the spinach greens or swiss chard, this insect can totally ruin your crop. So if you see this translucent, you know little narrow lines showing up on your your spinach leaves or or swiss chard leaves beet leaves, remove those leaves right away and put them in the garbage so that you're hopefully eliminating this pest from your garden and reducing it spread this out one that ones can definitely be problematic. And there are some you know diseases too, that leafy greens can get some of the mildews, wilts, viruses. So rotating as much as you can. Growing spacing things properly as much as you can and buying clean seed from a reputable Seed Company is going to be key.


Nate Bernitz  53:53

Yeah, spacing is one of those things where it's definitely tempting to try and move things closer together and you might be able to get away with it. But the closer you're growing things together, the less airflow there is and the more likely you end up losing your crop to a disease. So that's, that's one of many places where as gardeners, we have to make some trade offs and decide what our risk tolerance is.


Emma E  54:19

And that's a mistake I think every beginner gardener makes where you're trying to get as much out of your garden space as you possibly can. So you're packing things in really close together. But if you do observe the spacing requirements that are listed on the seed packet, you're going to have the best possible results and you are actually going to end up with more produce in the long run.


Nate Bernitz  54:43

And then lastly, what those cool season root crops that's where we ended up dealing a lot more with soil borne issues right because that that's what you're trying to harvest is below the ground and you know the in the end In a way that it's appealing to us, it's also appealing to some to some pests. So what are you worried about there? And again, how do you prevent and manage it?


Emma E  55:09

Well, rodents can sometimes be an issue in the garden, especially with root crops. One pest that is, I think particularly troublesome, especially in brand new gardens, where there was previously turf, is the wire worm. This is actually click beetle larvae. So these these little grubs that feed on root crops actually feed on a variety of different crops. And they'll they'll chew all these holes through your through your carrots, or parsnips or beets, which is really frustrating when you go to pull these up, and most of that plant has been ruined. So the key was something like that, once again, is rotating crops and ideally putting a crop into that space that isn't affected by the wire worm. So perhaps you're you're going to, let's say grow pumpkins there instead, next time, because those those don't tend to be impacted by wire worms so much, or maybe your your peas or beans.


Nate Bernitz  56:08

the message there, I think is if you're turning up a piece of your lawn into a garden, maybe that's not where you grow root crops for a few years.


Emma E  56:17

Yeah, exactly. Yep. Yep. So they tend to be the like, the biggest issue where you recently converted a lawn or field area into a vegetable garden. So maybe wait a few years on those root crops, maybe grow those in containers.


Nate Bernitz  56:31

one of the questions we get often is what can I treat my soil with, to deal with this disease, or this insect that's causing me problems. And I this isn't always true, but often, there is nothing you can treat your soil with. And I think that's true for wireworm. Right, there's not really a treatment available to home gardeners.


Emma E  56:53

Yeah, you're not going to be dumping pesticide in the soil to try to kill this pest. Just number one, not something that's that's gonna work. Number two, something that could be incredibly environmentally damaging. So these, you know, there really isn't an option there. And even for commercial growers with wireworms, the best thing they can do is rotate crops and grow something else in that area that isn't affected by this pest.


Nate Bernitz  57:25

All right, as we wrap up, I was thinking both of us could share our favorite cool season veggie. Why it's our favorite, and you have just any insight about it. Do you want to go first?


Emma E  57:37

Yeah, my favorite is probably radishes, believe it or not, which you might think like, Oh, that's kind of a funny thing to have be your favorite. But when I was a little kid and getting going or getting started with gardening with my mom, she would always let me pick out which radishes we were going to grow in the garden. And there's a really wonderful variety called easter eggs. And you get all these radishes that are different colors. So you get some that are that are pink, more of a lavender, red or white in this blend. And I always thought there's so much fun. I still love them on salads. I love eating them with hummus. So I get I get really excited about radishes and I like to try different varieties.


Nate Bernitz  58:21

Okay, so my favorite is also connected to my mom. So I'm loving that. I think this is the first time I've brought my mom up on this podcast, but she is a real evangelist for kale. And particularly my favorite kale is lacinato kale. And recently, I learned that lacinato kale was introduced just in the 1980s. And before that kale really wasn't a popular vegetable from a human culinary perspective. Apparently kale was mostly for poultry forage from the late 1800s into the late 1900s. And it's crazy to think about that because kale is so popular now. And I think that might be because lacinato kale in my opinion is just the the tip of excellence when it comes to kale there's there's nothing that even comes close to it. I believe my mom's favorite is red Russian kale. But we can agree to disagree on that. I mean, I like red Russian kale too, but I grow lacinato kale, I have a couple flats started and growing right now and I just can't wait to get out there and for me lacinato kale is awesome because you can eat it raw and eat it cooked and I think it's fantastic and both I love eating it raw in like a kale Caesar salad, where you just have to massage the leaves a little bit and it goes from bitter to just really tender and delicious, but I also do lacinato kale is a side dish just with olive oil, salt and pepper, lemon juice, red pepper flakes, things like that as basically a side dish to like any fish or meat or anything. It's it's on our plates often. I think the reason we bring this up is because there are obviously a lot of cool season veggies and veggies in general, they even grow, but you should grow what you like, some veggies are harder to grow than others. But even for the ones that are difficult, it's worth it. And you're willing to maybe put in the extra effort to overcome some of those challenges. Like say a tomato, it's really hard work, but it's totally worth it. So tons of people put a lot of effort into growing tomatoes. And for me kale is not actually very difficult at all. So that's fortunate because I love it, and I'm gonna grow out of it.


Emma E  1:00:49

Such a good point, Nate. And I guess the same is true for radishes. They're they're easy to grow. Pretty darn reliable, which is another reason why I like them. But if you're, if you're really excited about something, you're probably going to be able to grow it. So try something weird like kohlrabi this year.


Nate Bernitz  1:01:07

Yes, kohlrabi is actually is so underrated. I'm a big fan of sliced kohlrabi on the grill. So if you're growing kohlrabi, give that a shot. You'll be glad you did.


Emma E  1:01:35

This episode's featured plant is none other than garlic, Allium sativum, which is a member of the onion family. Garlic grows wild in Central Asia, and is one of the oldest known horticultural crops. There's actually historical evidence that it was used by Egyptian and Indian cultures as much as 5000 years ago. botanically speaking, garlic is a bulbous perennial. It has linear flattened grass like leaves, and some varieties produce a flower stock topped by a cluster of pinkish white flowers. If you grow garlic in your garden, it's important to know that it comes in two varieties, hardneck and softneck. The main difference between hardneck and softneck varieties is whether they form a flower stock. hardneck varieties typically produce a flower stock called a scape, which leaves behind a hard stem that runs through the middle of the garlic head. By contrast, softneck plants do not produce a flower stock, and they grow smaller bulbs with a larger number of cloves. softneck plants are bradeable which means that the tops can be braided together into attractive chains for storage. softneck garlic is what you'll usually find at the supermarket because it has a longer shelf life. As a general rule, hardneck varieties are hardier and better able to withstand New Hampshire winters. varieties that consistently do well in New Hampshire include Music, German Extra Hardy, and Russian Red. A bonus is that hard neck scapes are also a delicacy with a lovely mild garlic flavor when cooked. If you want to grow garlic, you'll need to plan ahead for the fall. The ideal time to plant garlic ranges from October to November depending on where you live. If you time it right, the garlic bulbs will have enough time to grow roots in the fall without sending up shoots before the winter and then you'll be harvesting your garlic the following summer. If you want to learn more, check out our awesome factsheet on growing garlic in the show notes. I'd like to close this episode with a few tips on harvesting cool season crops. The flavour freshness and nutritional content of vegetables is entirely determined upon the maturity and time of day when they're harvested. vegetables that are too mature, may be tough and stringy, or those that are picked too soon, maybe flavorless and have fewer nutrients. The time of day fruits and vegetables are picked and the way they're stored can also have a big impact on quality. A good general rule is to harvest vegetables during the cool part of the morning and store them as soon as possible. The length of storage and retention of nutrients will be maximized with optimal storage conditions immediately after harvest. For some crops, this means putting them in the refrigerator while others should be left out at room temperature. I don't have time to discuss harvesting all of the crops you might grow in the garden. But here are some tips on harvesting a few favorites. For lettuce, you'll want to harvest the older outer leaves from the basis of plants when they're about four to six inches long. Or if you're growing a heading type of lettuce. You should pick the entire head when it's moderately firm and before flower stalks begin to form. This usually happens once hot weather arrives. Lettuce will stay crisp if you store it inside of a plastic bag in the refrigerator immediately after harvest. Similar to lettuce, kale can be harvested by twisting or cutting off the oldest leaves at the base of plants when they're eight to 10 inches long, and a medium green color. Heavy dark green kale leaves are over mature and are likely to be tough and bitter. Store kale in the refrigerator too. And finally, if you grow onions, wait to harvest them until the tops fall over and begin to turn yellow. After digging or pulling them up, allow the onions to dry out in a Sunny dry place for a day or so to toughen their skins. A ventilated greenhouse is perfect for this. And finally, brush off dried soil. cut the stems leaving two to three inches attached and store them in a cool dry place.


Nate Bernitz  1:06:08

Well that's gonna do it for today's show on growing cool season veggies the ninth episode of Granite State gardening. As mentioned if you have unanswered questions about growing cool season veggies mark your calendar for April 19 at six o'clock, when we'll do an interactive Facebook Live talk and viewer q&a with myself and Becky Sideman. Email us at GSG dot pod@unh.edu follow us on social media at Ask UNH Extension and share this podcast with fellow gardeners. Until next time, keep on growing cool season veggies Granite State gardeners we'll talk again soon. Granite state gardening is a production of the University of New Hampshire Cooperative Extension an equal opportunity educator and employer views expressed on this podcast are not necessarily those of the universities, its trustees or its volunteers, inclusion or exclusion of commercial products in this podcast does not imply endorsement. The University of New Hampshire US Department of Agriculture and New Hampshire counties cooperate to provide extension programming in the Granite State. Learn more at extension.unh.edu




Extension Field Specialist, Community & Economic Development
Phone: (603) 678-4576
Office: Cooperative Extension, Nesmith Hall Room 204, Durham, NH 03824

Extension Field Specialist, Pesticide Safety Education
Phone: (603) 351-3831
Office: UNHCE Education Center, 88 Commercial Street, Manchester, NH 03101