The Dos and Don’ts of Mulching the Garden
Mulch properly to make the difference between a thirsty, weed-infested garden and a verdant, healthy paradise that’s the envy of the neighborhood.
Mulch is any material laid over the surface of the soil to retain moisture, suppress weeds, regulate temperature, and prevent erosion. Bare soil exposed to harsh sunlight means plant roots suffer and require more water; it’s also a literally open invitation to weed seeds. Mulch combats these problems, making less toil for you, the gardener, and in addition adds an attractive finishing touch around trees, shrubs, and flower beds that enhances curb appeal.
There are different types of mulches, however, and several tricks to applying it properly to get best results for blooms, veggies, just about anything you plant. So read on for the secrets to mulching the garden, then sit back and enjoy the grow!
DO use the right mulch for the job.
Organic mulches break down into the soil, adding nutrients in the process. They include chopped leaves, manure, straw, hardwood, grass clippings, newspaper, cocoa bean hulls, and compost, and are the best option for mulching vegetable gardens or mixed borders containing a combination of trees, shrubs, and perennials. Conversely, plastic, gravel, and shredded rubber tires are all inorganic mulches that remain in place until you move them. Certain vegetables like tomatoes and peppers benefit from the soil-warming ability of plastic mulch.
DON’T use too little—or too much—mulch.
Three to four inches of organic mulch like hardwood or cocoa bean hulls applied around a plant or tree, but not touching it, is ideal for suppressing weeds, maintaining proper soil temperature, and conserving water. Be especially careful with hardwood mulch against your home’s foundation: Piled too high, it’s an invitation for termites. To prevent an infestation, only apply mulch there if absolutely necessary, tapering it so that the layer thins as it nears the house and leaves six inches of concrete is exposed.
DO time it right.
Timing is everything when it comes to mulch. In general, mulch applied in early spring prevents soil from warming, restricting early-season plant growth. The exception is plastic mulch, applied in early spring on a vegetable garden prior to planting: It will raise the soil temperature to give seeds a healthy early start. (You can leave it in place for heat-loving vegetables like tomatoes, peppers, and eggplants, but because plastic isn’t permeable, ensure that these plants receive enough water.) Cover the area around trees, shrubs, and perennials with an organic mulch when the soil warms and dries out, which could mean waiting until June or July, depending on location. Cool-weather crops like greens, broccoli, and cauliflower do better with soil-cooling organic mulches applied at the time of planting at least an inch away from plant stems to prevent rot problems.
DO consider organic materials on your property that can be converted to mulch.
Give your wallet a break with the mulch-to-be goldmine on your property. If trees are plentiful, shred fallen leaves with a lawn mower and add to your veggie patch in the fall. Growth-inhibiting chemicals in leaves known to stunt young plants and seedlings will have plenty of time to break down in time for spring planting. Or pile fallen leaves in an area of the yard, protected from wind, where they can decompose to form leaf mold. It takes six to 12 months to break down, but the result yields an excellent soil conditioner for mulching the garden. Grass clippings, as long as they haven’t been treated with herbicide or any other toxic substance, are another good choice. Give them a day or two to dry out before mulching around plants.
DON’T volcano mulch around trees.
Volcano mulching—when woodchip mulch is piled high, tight, and thick around tree trunks so that it resembles the shape of a volcano—is a common but unfortunately destructive practice that prevents water and oxygen from reaching the roots. What’s more, as hardwood mulch begins to breakdown and decompose, the temperature in the mulch rises, subjecting the tree trunk to damaging temperatures. The result is a tree that may become unable to transport water and nutrients. When landscaping around trees, two to three inches of woodchip mulch—not touching the tree trunk and distributed out to the drip line (the area directly below the outer circumference of branches)—is enough to keep roots cool and conserve moisture.
DO consider the health and well-being of your pets.
Most mulches are very safe for our four-legged friends. In fact, many dogs, and even some cats, may nibble on a wood chip or two with no adverse effects. The American Veterinary Medical Association (AVMA) advises homeowners to avoid cocoa bean mulch, also called cocoa hulls, due to its toxicity to dogs and cats. Like chocolate, another pet poison, they contain caffeine and theobromine, which can cause heart problems and gastrointestinal issues. Ingesting too much of any mulch will likely result in vomiting and diarrhea. Chunky mulches like woodchips or rocks can cause life-threatening bowel obstructions.
DON’T mulch with rocks.
Yes, they’re abundant and pretty, but rocks offer no benefits to your soil and can do more harm than good in your garden. Rocks heat up quickly in the sun and hold onto heat, which in turn can raise soil temperature, resulting in stressed, thirsty plants. Windblown weed seeds also nestle among the rocks and root in all the nooks and crannies, making weeding even more of a chore. Especially avoid rocks around common foundation plants like azalea, hydrangea, and yews; these plants thrive in acidic soils (those with a pH level below seven), and rock mulch elevates soil pH, making an acidic soil more alkaline. Opt for an organic mulch instead and collect those stones for a rock or cactus garden, where they belong.