2012-05-31 / News

Mulches for the ages

Over the years my vegetable garden has benefitted from a 2-inch layer of compost that I add most springs to keep the weeds in check. In most cases, I can push a hand about a foot deep into the soil without hitting a rock. Fruiting shrubs have also benefitted from having a layer of compost spread around their base. Even potted plants come in for their share of compost. It is spread about an inch deep on top of the potting soil. The compost serves as a biodegradable mulch that helps suppress weeds, but also gives the plants a nutrient boost. However, that is not the case with most mulches.

Many mulches – especially wood chips and pine bark – absorb nutrients from the soil as they degrade. Thus, with the heat and dryness of summer coming ever nearer, it pays to look at how to mulch your garden beds and provide nutrients for your plants.

The first job before spreading any mulch is to suppress weeds. Professionals simply spray the area with Roundup or some other weed killer and call it a day. Amateur gardeners are probably better off hoeing the surface of the soil to kill off any weeds. If you leave weeds growing – even partially – they will grow back through the mulch. If you wish, you can apply a weed mat over the area to be mulched, but I have found that weeds simply grow up through the holes in the mat. (This makes it easy to remove them later. Simply rake off the mulch and roll up the mat. The weeds usually come with it.)

A far better idea is to sterilize the soil if you want to suppress a large area. This is easily done by spreading a large piece of clear polyethylene over the area, weighting the edges down, and leaving it in bright sunshine for about 10 days to two weeks. The heat created under the polyethylene is usually enough to kill off weeds and weed seeds.

If you have plants in the area to be mulched, your plants will love you if you spread some compost or fertilizer around them before applying mulch. Only after all these preparations are made should you mulch the area.

So what type of mulch should you use? There are many types of mulch: pine bark, hemlock, cocoa brown, crushed shells, small stone, wood chips, and the aforementioned compost are just a few. You can also use newspapers, cardboard, plastic, shredded tires, stone dust and gravel.

Colored-bark mulches tend to retain their color for at least one season, often two before they fade. They also come in several colors. Dave Ruggieri, president of Hopedale Trucking where I get all my mulch, makes three colors of wood-bark mulch. The most common is red (using iron, as in rust), black (with carbon), or brown, made with a mixture of iron and carbon.

“All the materials are organic and occur naturally in soils,” he said. “As long as mulch has bark in it, it will not harbor insects. That’s why pine park mulch is so good. It is illegal to treat mulch with insecticides.” Hopedale Trucking will deliver mulch right to your doorstep in loads of up to 20 cubic yards – but you have to spread it!

When spreading mulch, I like to put down flattened cardboard on the soil first. The cardboard prevents weeds from coming up through the mulch and eventually rots away. Cardboard, after all, is made of wood pulp. With the cardboard in place, the mulch can be applied. A layer 2 to 3 inches thick is best. If the layer of mulch is too thick, it can actually prevent moisture from reaching the plant roots.

When applying mulch around trees and shrubs, only bring the mulch to the present level of the roots – don’t bury the lower part of the trunk. If you do, you provide a perfect opportunity for mice to tunnel under winter snow through your mulch and chew on the tree bark. Taper the level of your mulch near the edges so that you don’t get mulch washing out of the garden bed.

That’s all there is to it. Spread your mulch and enjoy a weed-free summer.

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