Low-Down on Mulch
Mulch is a favorite because it unifies the overall look of landscaping and promotes healthy plant growth. When properly applied, mulch suppresses weeds and helps the soil retain water. It also insulates plants’ roots, cooling them in the summer and warming them in the winter. Here are some things to think about when choosing mulch for your yard or garden:
- The Mulch and Soil Council: You may have noticed that some brands of mulch are certified by the Mulch and Soil Council, a national non-pro fit trade association that sets industry standards. It’s important to understand that the MSC is not a government regulator or an environmental watchdog. It is an industry trade group with a lot of corporate backing (including Scotts of Roundup fame).
- To Dye or Not to Dye? Some consumers are concerned that the dyes in colored mulch might be a problem, especially when used in kitchen gardens or around fruit bushes. According to the Mulch and Soil Council, most mulch dyes are vegetable-based, and therefore safe. But author George Weigel is skeptical of these claims. As Weigel explains in his article “Do Colored Mulches Harm Plants?” there are “too many unknowns.” Figuring out exactly what’s in a particular bag of colored mulch is close to impossible, so we advise caution. After all, the dye in colored mulch is for aesthetic purposes only. For those ready to embrace a more natural look, un-dyed mulch products are a very smart choice.
- Chromated Copper Arsenate (CCA): Sound unpleasant? It is. CCA is an insecticide used in older pressure-treated lumber, and mulch made from recycled wood poses a risk because it can contain harmful levels of arsenic. The Mulch and Soil Council tests for the presence of CCA and does not certify any brand that fails the test. And while we take MSC’s stance on dyed mulch with a grain of salt, MSC is the only organization offering anything close to comprehensive testing for CCA. Therefore, we do recommend looking for the MSC certification on the label when buying mulch.
- Best Bets: Natural un-dyed products like Pine Straw, Pine Bark Nuggets, and Cypress Mulch are great alternatives for everyday mulching. Check with your local plant-nursery staff or a landscaping professional if you’re not sure exactly which of these will work for your situation.
- DIY Mulch: You can create natural mulch right in your own backyard. Just run a mower over fallen leaves to cut them into the right size for mulching (a bagging mower is ideal for this). In most cases, leaves make better mulch than grass clippings, because the grass can mat together into a tight mass. Chopped leaves have a looser consistency and are less prone to problems like mold growth.
- Too Much of a Good Thing: Don’t put a big pile of mulch right around the base of a tree. “Volcano-Mulching,” as this is called, can suffocate the roots and promote rotting of the lower trunk. The volcano also gives a leg up to rodents that like to chew on bark. For mature trees it’s best to spread only a very thin layer of mulch approximately a foot-and-a-half around the base of the tree and then a thicker layer (3-4 inches deep) as far out as you want. Newly transplanted trees do best inside a donut-shaped ring with no mulch covering the area directly above the root ball. For more information go to the University of Georgia’s Agricultural Extension website and check out Keith Mickler’s article Too Much Mulch Can Kill Trees.