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Friday, September 29, 2023
Sept. 29, 2023

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Gardening with Allen: Got weeds? Get mulch


My husband and I spent all Saturday afternoon weeding our vegetable garden and all of our beds. Is there some way we can avoid repeating this a few weeks from now after the weeds have grown back again?

When you weeded, you turned up a whole new crop of weed seeds that will sprout now that they are exposed to the sun. If you cover those weed seeds with mulch, they will no longer be able to see the sun and 90 percent of them will not grow. Mulch also provides a physical barrier so most of the rest will not grow either.

The most popular mulch material is bark. Bark is available in two different size chunks and finer sizes called bark dust. Other materials commonly used for mulch include compost, grass clippings, leaves, lava rock, pea gravel and river rock. I have a flower garden next to a large evergreen tree that drops needles. I leave these needles as a mulch. My wife prefers the appearance and uniformity of bark dust, so we cover the needles with an inch of bark dust.

You can achieve 100 percent weed control for trees and shrubs by covering the ground with landscape fabric and then covering the fabric with a granular mulch for appearance. Weed barrier fabric is a black or gray woven plastic cloth that is porous so water and air can pass through. It will normally last for several years as long as it is covered with granular mulch, so sunlight does not deteriorate it. A few weed seeds will eventually blow in on top of the granular mulch. However, they are very shallow rooted and easily controlled.

Polyethylene plastic should be used only for vegetables, with holes around each vegetable plant. If it’s used around larger plants like trees and shrubs, they will not get adequate irrigation. Plant roots grow close to the surface in order to get enough oxygen. Trees and shrubs need deep, anchor roots for support. Black or red poly mulch not only controls weeds around heat-loving vegetables like tomatoes and melons; it also heats the soil underneath, which speeds growth.

I use grass clippings as a mulch for vegetables. It turns brown as it dries and condenses. I just add a new layer every couple of weeks. It gets tilled in with the chopped-up vegetable plants at the end of the growing season.

Multiple layers of newspaper also make good mulch for vegetables. However, it is necessary to put some soil on the edges to hold it in place.

Organic mulches such as bark and compost are converted by worms and micro-organisms into humus and eventually release nutrients to the plants growing underneath them.

Typically, bark and compost mulches are added every year or two. Organic mulches also improve water penetration and reduce water evaporation.