Overlap the strips of black plastic weed barrier so weeds can’t sneak their way through the edges of the material.
Apply a 2- to 4-inch layer of organic mulch over the entire surface of the black plastic weed barrier. Spread the mulch over the edges of the weed barrier so the black plastic doesn’t show.
Things You Will Need
Weeds are the enemy of gardeners around the country. These pesky plants decrease the beauty of your yard and rob vital moisture and nutrients from your flowers, vegetables and lawn. Mulch helps minimize weeds but also retains more moisture and helps moderate the temperature of your soil. The trick to keeping weeds from growing through your mulch is to put a layer of weed barrier underneath.
Use several layers of old newspaper in place of black plastic weed barrier if you want a more environmentally friendly way to reduce weed growth through your mulch. Lay the newspaper down and cover with a 2- to 4-inch layer of organic mulch. You’ll have to replace the newspaper and mulch more often, however, because the newspaper will biodegrade over time. Fabric weed barriers are another option, though they aren’t always as effective as plastic in preventing weeds from growing.
Black plastic weed barrier
If you haven’t applied mulch yet, landscape fabric or weed barrier cloth is a safe way to block weeds while still allowing water to pass through to the soil. Unfortunately, landscape fabric isn’t a perfect solution because some determined weeds will push through the fabric, and those weeds will be extremely difficult to pull.
Other than hand-pulling, mulch is probably the single most important means of weed control. However, mulch works best when used as part of a multi-pronged approach along with pre-emergent herbicides.
Mulch acts as physical barrier against weeds, but it must block sunlight in order to be effective. If you notice weeds coming up in mulch, you may need to thicken the layer as blocking light generally requires at least 2 to 3 inches (5-7.6 cm.). Replenish mulch as it decomposes or blows away.
To stop weeds in mulch with pre-emergent herbicides, begin by raking mulch off to the side, then hoe or pull any existing weeds. Apply the product, following manufacturer directions to the letter. Pay attention to the label, as some plants don’t tolerate certain types of pre-emergent herbicides.
How to Kill Weeds in Mulch with Herbicides
Weed control is one of the primary reasons for applying mulch, yet pesky weeds may persist, even through a carefully applied layer of bark chips or pine needles. This happens when weed seeds are buried in the soil or are distributed by birds or wind. What should you do if you’ve got weeds coming up in mulch in spite of your best intentions? Keep reading for a few helpful tips.
Sometimes, good old hand-pulling is still the most effective way of getting rid of weed growth in mulch.
A Note about Glyphosate: You can use glyphosate to stop weeds in mulch, but this approach requires extreme care because glyphosate, a broad-spectrum herbicide, will kill any broad-leaved plant it touches, including your favorite perennials or shrubs. Apply glyphosate directly to weeds, using a paintbrush. Be extremely careful not to touch nearby plants. You can also protect plants by covering them with a cardboard box while you’re applying the herbicide. Don’t remove the box until the treated weeds have time to dry completely.
Getting Rid of Weed Growth in Mulch
Replace the mulch carefully, being careful not to disturb the just treated soil. At this point, you can provide extra protection by applying another layer of herbicide over the mulch. A liquid herbicide works best because it adheres to the mulch instead of falling through to the soil.
When used correctly before weeds sprout in early spring, pre-emergent herbicides are one effective way to prevent weeds coming up in mulch. They won’t, however, do anything for weeds that have already sprouted.