Mulching Trees and Shrubs [video]

In this video, UNH Cooperative Extension state specialist, Cathy Neal, discusses mulches and mulching. See a full transcript below.

Video Transcript

Hi.  I'm Cathy Neal, Landscape Horticulture Specialist with UNH Cooperative Extension. Today's topic is mulches and mulching. We'll talk about kinds of mulch you might use, how to properly apply the mulch, when you can mulch, and what the benefits are. So mulching is good, right? Mulches do a lot of good things. They mostly help prevent weeds from growing up around your plants and competing for space, water and nutrients. But, they also help conserve soil moisture and they help feed the soil. As the organic mulches decompose they help feed the soil organisms which creates a good root environment for your plants.

What type of mulch you choose to use has a lot to do with your personal preference, but also there are differences in particle size and characteristics of some of these mulches. This is a very fine textured, aged bark mulch here which is very nice for annuals and perennial beds. You can also get a very coarse texture in mulch as in these utility wood chips. These are great for trees and shrubs where perhaps appearance isn't quite as important.

We have two examples of bagged mulches here. The dark brown is a shredded cedar mulch. You can see that wood has been passed through a shredder and given it this nice texture through which water will pass quickly and not stay saturated and encourage root growth up into it, which we don't want. The red mulch is usually made from something like ground pallet wood and then sprayed with a colorant to give it this red color, and it usually has a very short life. Because it is soft wood it breaks down very very quickly and you'll have to renew that mulch sooner than some of these other ones.

When figuring how much mulch to buy you have to estimate the size of the area to be mulched. A 3 cubic foot bag of mulch will cover 12 square feet of area, or  enough for a tree circle 6 to 8 feet in diameter. A full-size pickup truck holds about two and a half cubic yards of mulch if it's filled all the way full -- enough to mulch about 300 square feet of area. You can also find mulch calculators online simply by searching for mulch calculators.

Today I'm going to be replenishing the layer of old mulch around this gorgeous planting of winterberry. You can see that the old wood chips have degraded and decomposed and there's a lot of roots starting to grow up into this area. We don't want to remove the old mulch, however,  because of those roots. We're just going to add a thin layer of new mulch to replenish it and make it look nice. I'm going to check my mulch depth again and make sure that it's not too deep. We only want three inches of mulch. And, what do we have? About five. So, I'm going to move some of this back.

Mulch can be applied at any time of year, but is most often done in the Spring when people are cleaning up and planting new plants after the ground thaws, and before we start to germinate. And, recheck it. So if you don't have a ruler, most people's hands their fingers are about three inches long so that would be the proper depth. The other thing to do at the end is pull back the mulch from the trunk of the tree or shrub, or if you have smaller plants around the crown of the plants. You don't want to keep the base of the plant too moist or you'll encourage diseases, fungi, even insects, and in the winter rodents along there. So pull the mulch back so you can see the soil. So, as we're finishing up mulching this winterberry notice that we have mulched the entire bed instead of individual plants. That makes our maintenance easier for weeding later on, and it also makes it look very nice.

You can also use pine needles, leaves or straw for mulching. These are more appropriate for mulching your vegetable garden where you don't mind if the product breaks down very quickly or mulching a new planting - especially from seed. So, if you start a lawn from seed, or in this case, a wildflower meadows from seed you put a light layer of mulch on it to help conserve soil moisture while that seed is germinating. Sometimes you'll see rocks or other inorganic materials used as mulch. Unless you have a personal preference for the way this looks, consider that your plants will be happier if you use an organic material that slowly breaks down and contributes to soil quality.

This is a good example of why we don't recommend putting landscape fabric underneath your layer of mulch. As the mulch has decomposed, the weeds have taken hold here on top of the landscape fabric and made quite a mess. So, we're going to fix that today by ripping out the landscape fabric and remulching it properly. Alright, so mulching is one of the best things you can do for your plant, or one of the worst things you can do to your plant if you don't do it properly. In this case, this is called a volcano mulch, and you see this quite commonly where mulch is piled up as much as a foot or even two foot deep around the base of a tree. That's very harmful to the plant because it keeps the base of the trunk wet, encourages diseases, insects and even rodents. It also can keep the soil too wet underneath it so that the roots can't get oxygen-- and yes roots do need oxygen.

If we took the same amount of mulch and spread it wide, instead of deep , it would be perfect. So we don't need more mulch to mulch properly we just need to distribute it in a three inch layer --and the wider you can mulch the better. Mulching through the drip line of a tree is a good practice. Even been pulling that back away from the trunk to let that bark dry out at the base. There!

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