Fall Vegetable Gardening

Tips for the Home Gardener in New Hampshire
Radishes

By August it may seem that the vegetable garden is winding down. Many of the early season crops like spinach, lettuce and peas are long gone, leaving just warm season vegetables such as tomatoes and squash. As summer begins to draw to a close, gardeners may be looking at putting their garden to bed until next year.

However, from late July through August is actually a great time to sow many vegetables for a fall harvest. In some ways, it is easier than growing in the spring because there is less annual weed pressure, and many pest insects have already completed their lifecycles. Also, with cooler temperatures, and hopefully increased precipitation, you should be able to easily extend your fresh produce season.

Deciding Which Vegetables to Grow

The best vegetables to grow in the fall are those that mature quickly and prefer cooler weather. This includes the majority of the cool season vegetables, or in other words, the vegetables that have some frost tolerance. Deciding which plants to grow in your fall vegetable garden requires a few considerations. First, it is important to establish when you expect the first freeze (32℉ or less) to occur.

Those with garden journals may have kept this sort of data for their garden over a number of years. If you haven’t paid attention to or recorded frost dates in your area, you can rely instead on generalities for NH regions. In central and southern NH, the first freeze usually comes in early to mid-October, and in mid-to-late-September in northern parts. Of course, this is just based on averages. The date of the first freeze varies from year to year, and even between relatively close locations, based on factors such as elevation.

Once you’ve established when you think the first hard freeze will occur, then it’s time to decide what you’ll grow. Start by looking at the days to maturity on seed packets to see if crops will have enough time to mature before a hard frost. Keep in mind that many crops can be picked a little young, such as spinach, lettuce, carrots, beets and turnips.

Others, like radishes and broccoli, are much better if they can be allowed to fully develop. Look for varieties that have the fewest days to maturity, as these will likely yield the best harvest. Remember that days to maturity are just estimates and are based on the time it takes from germination to harvest, not on when seeds are planted.

Some fall vegetable crops are more frost tolerant than others. Carrots, broccoli, cauliflower, lettuce, mustard greens and spinach can handle light frost without injury. Other vegetables may be able to stand up to hard frost, such as beets, kale, collards, radishes and bunching onions. Having a general idea of the cold tolerance of a crop is helpful for planning both what and when to plant.

Fall Vegetable Planting Chart
 
Vegetable Days to Maturity Vegetable Days to Maturity

Beets

55-65 Kohlrabi 50-70
Broccoli 60-80 Leaf Lettuce 50-60
Bunching Onions 50-65 Head Lettuce 60-85
Carrots 60-80 Mustard Greens 40-50
Cauliflower 55-60 Peas 60-80
Cilantro 50-55 Radish 25-30
Collards 55-70 Spinach 50-70
Daikon 55-60 Swiss Chard 60-75
Kale 55-70 Turnips 40-60

Starting Fall Vegetables

Most fall vegetable crops can be directly sown in the garden or started indoors and transplanted into the garden. Seeding outdoors when the weather is hot can sometimes be problematic because cool season vegetables germinate best at lower temperatures. One way to get around this is to shade and water the soil before you sow. Placing shade cloth over the area you intend to plant is a great way of reducing the temperature and improving germination.

 Additionally, it is very important to pay attention to watering. Seed beds will dry out much faster in late summer than they do in the spring, and it may be necessary to water multiple times throughout the day to keep the top inch of soil evenly moist until the seeds germinate and the young seedlings become established. In many ways, starting seeds indoors and moving transplants into the garden is much easier and more reliable. It also allows you to grow crops in the fall that have more days to reach maturity. 

Extending the Growing Season

Those who want to extend their gardens into the fall may need to consider protecting their plants from hard frost. Many fall vegetables do fine through mild (minimum 28℉) or brief frosts, but hard freezes can cause some damage. Covering plants with row covers or anything else breathable such as towels, blankets or sheets, can help keep them alive longer. By covering plants, radiant heat from the ground is trapped, preventing them from freezing. Just make sure to remove coverings in the morning as soon as the temperature is above freezing to avoid cooking the foliage.

A trick for keeping crops growing longer is to apply a thick layer of mulch over the soil around them. Mulch helps moderate the soil temperature by providing a layer of insulation. It keeps the soil cooler in the heat of the summer and warmer in the fall as the days and nights begin to get colder. Mulch also helps conserve soil moisture, especially while the temperature is still hot.

Planting a Cover Crop

If keeping the vegetable garden going into the fall feels like too much work, another great thing you can do is plant a cover crop. Cover crops can be a huge benefit to the garden by reducing erosion, keeping weeds in check, and adding organic matter to the soil. Oats, winter rye and tillage radish are all excellent choices for home gardens.

Oats germinate quickly and die over the winter, making them a good fit for no-till gardens and raised beds. Winter rye is nice for garden beds that you will plant in late spring with warm season vegetables (like tomatoes, peppers and cucumbers.) because it will survive the winter and begin growing again in the spring. However, it will need to be manually turned under or tilled before planting. If your garden soil is compacted, tillage radishes are perhaps the best cover crop because they grow deep roots that break up the soil and are winter-killed.

Though late summer is often the time we start to think about putting the garden to bed, many cool season vegetable crops are perfect for extending the season and keeping fresh vegetables on the table.


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