It’s one of the basics of any garden. Mulch blocks weeds, regulates soil temperature and moisture, fights erosion, and keeps gardens looking neat and trim. Yet some mulch can actually harm your plants and the environment. By minding your mulches, you can find mulch that is both garden- and eco-friendly.
A mulch to avoid
Shredded cypress is one of the most popular mulches on the market. However, this relatively low-priced mulch comes with high environmental costs. According to University of Florida data, timber companies grind some 129,000 tons of the state’s cypress into mulch each year, part of a cycle that takes nearly 3 million more cubic feet of cypress than it replaces.
Cypress thrives in freshwater wetlands, where it stores and filters water resources and provides a vital wildlife habitat. This graceful native tree grows slowly and, once cut, is difficult to replace. Today logging companies clear-cut younger stands, and though mill remnants make up some cypress mulch products, entire trees make up others.
Cypress also has some mulching drawbacks. Shredded cypress, like many other shredded woods, will fade in color and decay within a year or two. Cypress mulches can also form fungal mats that inhibit water drainage.
Unlike cypress, renewable eucalyptus grows rapidly on commercial plantations. The mulch’s pleasing scent doubles as a deterrent to fleas and other lawn and garden pests. Eucalyptus also retains its color longer than cypress, aging from golden yellow to reddish tones. You may need to replace eucalyptus more frequently than pine bark or other wood chips, however, because it settles into the soil.
Exotic Australian melaleuca (Melaleuca quinquenervia), or paperbark tea tree, has invaded more than half a million acres of Florida wetlands. Spreading rapidly by fire, melaleuca has turned vast portions of the Everglades’ saw grass prairie into dense, monoculture forests. Forestry Resources of Fort Myers, Florida, has joined environmental groups seeking to remove melaleuca. The company processes melaleuca into mulch and other products and helps replant native cypress.
Termites do not favor melaleuca, the mulch will not significantly alter soil pH, and it holds its shape well.
Tired of lugging around heavy bags of mulch? Cocoa hulls, available in many larger and regional garden centers, are both lightweight and a feast for plants.
The byproducts of commercial cocoa grinding, these small, shell-shaped hulls contain 2.5 percent to 3 percent nitrogen. Their low acidity makes them an ideal choice for roses. Snails and slugs are said to shy away from this mulch, but dog owners should beware, as cocoa hulls contain theobromine, the chemical that makes chocolate toxic for canines. Cocoa mulch may develop a layer of harmless mold that can be removed with water or raking.
Pine bark and needles
Woodsy pine bark chips retain their shape and color longer than shredded wood mulches, while pine needles can nourish acid-loving plants. Usually obtained as byproducts of other lumbering uses, these commonly found mulches make use of resources that might otherwise be wasted. Pine bark chips do tend to float away in heavy rain, making them unsuitable for sloped landscapes.
Old tires can have new lives as mulch. A number of companies sell shredded rubber mulches in long-lasting natural and fanciful tints. This inorganic mulch is soft on gardeners’ knees and won’t fall prey to hungry insects. For even less maintenance around trees, look for preformed, recycled rubber tree rings.
A local rubber mulch producer may be nearby. If not, many garden centers now carry recycled rubber mulches, and some companies will ship this specialty mulch to you.
Local resources such as straw, peanut and pecan shells, corn husks, chemical-free sawdust, or composted manures work well as mulch. Some tree service companies will unload truckloads of chippings at your doorstep. When using freshly chipped wood, be sure to add a nitrogen fertilizer to offset decaying wood’s tendency to tie up soil nitrogen. Also call around to local landfills and recycling centers. Many provide free tree waste mulch.
Make your own
Shred nonglossy newspaper and spread it several inches thick, then dampen and cover with a thin layer of wood mulch or grass clippings. To block weeds further, lay down several full sheets of newspaper.
Instead of bagging, shred autumn leaves with a mower. Compost the leaves for a season into “leaf mold” or spread in a loose, six-inch mulch layer that will compost in place. Other lawn materials such as fallen twigs, hedge trimmings, and Spanish moss also make fine mulches.
You can have too much of a good thing. Overly thick mulches can suffocate roots. Most mulches work best in two- to four-inch blankets.
When mulching trees, mulch out to the tree’s drip line but leave a few inches bare around the trunk where piled mulch could harbor wood-harming pests and lead to devastating trunk rot. If mulch becomes hard and matted, fluff to allow air and moisture to get through. Also always check the freshness of bulk mulches. If mulch smells sour or rotten, it could harm your plants.
When to mulch
In colder climates, a good replenishing layer of organic mulch just before freezing can help plants and bulbs weather winter extremes. Allow soils to warm up a bit in spring before applying new mulch, which will keep soil temperatures as much as ten degrees cooler in the hotter summer months and prevent disease susceptibility. By periodically mulching or installing long-lasting mulch beds, you can keep up with your garden’s mulching needs and enjoy mulch’s many benefits.