How to Use Mulch in Your Garden

Mulch solves so many problems it ranks pretty high on a gardener’s list of best friends. Mulch controls weeds, keeps soil moist, and prevents erosion and runoff. Organic mulches enrich the soil when they decompose, adding nutrients and improving soil structure. A blanket of mulch maintains even soil temperature, which promotes healthy plant growth. In winter in northern climates, for example, mulch keeps the soil from the freezing and thawing that disturbs root systems. Mulch also makes a garden look good, giving beds a consistent and finished appearance.

What to Use for Mulch

The best mulch materials are free or inexpensive and available locally, even in your own back yard. Leaves make terrific mulch, especially if you chopped them up first. (A lawnmower is good for chopping leaves.) Leaves left to decay for a few years make leaf mold—great for the soil. Grass clippings make good mulch—but only if they have not been treated with herbicide because herbicide residue can kill your plants. Spread grass clippings thinly or they will get moldy and clumpy. Compost is the ideal mulch; just spread it on top of the soil instead of mixing it in. Although not very attractive, newspaper (don’t use glossy or colored paper) is a good mulch; top it with leaves or grass clippings and you won’t even know it’s there.

Depending on where you live, you might have free access to seaweed, cedar shavings, or pine needles. Pine needles increase the acidity of the soil, so you might want to reserve them for acid-loving plants like azaleas and blueberries. Some towns keep piles of wood chips for residents to use. If arborists are doing tree work in your neighborhood you can ask them to drop a pile of chips in your yard. Fresh chips actually use up nutrients as they age, so save them for a few months before you put them on your garden.

If you can’t find enough free or almost free mulch, you can certainly buy it. Hay and straw are popular mulches for vegetable gardens; straw is less likely to have weed seeds so it’s a better choice even though it is usually more expensive. Flower and shrub borders mulched with bark chips look very professional. You can buy bark mulch in bags or by the truckload. Be sure you know what kind of mulch you are buying; you’ll want to avoid cypress mulch, for example, because it’s made from endangered bald cypress trees.

Stones, shells, and other inorganic materials make attractive mulches. While they don’t add nutrients or improve soil structure, they do keep weeds down and the soil moist. Plastic, rubber, and other synthetic mulches may be useful in certain situations. If you’re using stone mulch, decorative garden stones often look nice placed in the garden beds nearby.

How to Apply Mulch

Remove weeds before you mulch. Three inches is the recommended depth for applying most organic mulches. If your leaves are dry, spread them about six inches deep. Three to six sheets of newspapers are enough. To protect plants from insects and diseases leave at least an inch between the mulch and the stems of the plants.

The best time to apply mulch depends on what you are growing and your purpose for mulching. For flower or vegetable gardens it’s best to wait until the ground warms up; otherwise the mulch will keep the soil temperature low and inhibit plant growth. Wait until seedlings are a couple of inches tall before mulching around them. If you want to keep soil temperature from fluctuating during the winter, apply mulch after the ground freezes.

Want to learn more about using mulch in your garden?

We’ve just scratched the surface of the topic of mulch, and it’s an important subject for any gardener. To learn more about the what, why, and how of mulching, check out these sites:

The U.S. Department of Agriculture Natural Resources Conservation Service has an excellent guide to mulching.

North Carolina State University offers guidance on mulching trees and shrubs.

The University of Georgia College of Agricultural & Environmental Sciences
Cooperative Extension Service has a fact sheet on mulching vegetables.

Lynne Lamstein gardens in Maine and Florida and is currently working on a sustainable landscape. She has a degree in ornamental horticulture from Temple University.