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Mulch in Colors Nature Never Knew

By Adrian Higgins
Washington Post Staff Writer
Thursday, April 28, 2005; Page H01

For gardeners who care about trends, an old product suddenly has become daringly different.

Colored mulches are the fastest growing segment in the huge but unquantified mulch trade. Although sales of such sober tints as black and dark brown are growing, "the most popular is the red for whatever reason," said Steve Titko, a mulch guru at Scotts Miracle-Gro Co. in Marysville, Ohio.


Cocoa shells are the byproduct of chocolate making and create a long-lasting and attractive mulch. It may prove a hazard to dogs that eat it.

These pigmented mulches are meant to retain their fresh look for a full growing season. Natural mulch, dark and rich-looking when laid, is soon bleached by the sunlight.

The Scotts version of red mulch is actually subdued compared with others. Coastal Supply Co. in Dagsboro, Del., offers a brighter shade. "If you like it, go for it," said Steven Liffers, Coastal's chief operating officer. "We put it around our house, and it's bright."

Bright red mulch is nothing more than an acknowledgment that mulch is as much for the gardener as it is the garden, perhaps more so. Mulch hides hardpan clay. It forms a neat, unifying rug in new beds until the plantings mature. It tidies the late-winter garden before plants erupt.

And now it comes in a range of colors.

For the garden, however, mulch is better laid in May than March. Spread it too early, and you retain winter's chill in the soil and risk smothering emerging perennials and spring bulbs.

And as lush as the designer mulch seems, its colorants may be hiding more than just its tendency to turn pale. Colored mulches are used by some producers to mask that they are made of recycled scrap, including wood pallets.

Wood from pallets is not inherently bad for the garden, but it is more likely to be part of a waste stream that includes building construction and demolition products that may contain pressure-treated woods impregnated with copper, chromium and arsenic.

Protecting the integrity of an unregulated product has been "the hottest button in our industry," said Titko, who is officially director of technical services for growing media at Scotts. The company has joined other members of a trade association, the Manassas-based Mulch and Soil Council, to establish voluntary regulations for mulch sources. In order to get council certification, the products are tested for heavy metals and other contaminants at a laboratory run by North Carolina State University.

The council's certification requires manufacturers to meet standards for selling bark mulch, which is considered by purists superior to mulches made from shredded wood. Bark mulch doesn't break down as quickly as wood, is not as attractive to termites and doesn't deprive plants of nitrogen in the same way that wood mulch does as it decays. (Both types are made by large and powerful grinding machines.) A product labeled, "bark mulch" must have at least 85 percent bark, said Robert LaGasse, the council's executive director.

Scotts mulches are made only of hardwood or pine bark, or of rot-resistant cypress and cedar with barklike qualities, said Titko. Coastal Supply's colored mulches are made from wood, but the company does not use pallets or other recycled wood, said Liffers.

Wood mulches function like bark mulches but can take nitrogen from the soil as they decay. As a general rule, the smaller the particles, the faster the wood decays from mulch to soil-building humus and, correspondingly, the larger its appetite for nitrogen. Smart gardeners lay some form of nitrogen fertilizer with the mulch to compensate; otherwise, you risk leaf yellowing and stunting in nitrogen-starved plants.

But just as buying mulch can be fraught with problems, so can using it. Mulches conserve soil moisture, suppress weeds and can shield foliage from soil-borne diseases. Organic mulches build the soil as they decay. Experts recommend a layer of two to three inches.

Laid too thickly or incorrectly, it can do far more harm than good. Mulch that is too thick will prevent moisture, air and nutrients from reaching the soil and become a growing medium for plant roots. When the mulch decays, roots are left exposed to the air, with disastrous results. Another common problem is the piling of mulch against the base of trees and shrubs. This cooks bark, promotes more inappropriate root growth and can also harbor bark-chewing rodents. Some material, even when laid thinly, can form an unwanted soil barrier, notably matted grass clippings, unshredded fall leaves and unamended peat moss.

Andre Viette, a perennial nurseryman in Fishersville, Va., cautions against laying organic mulches on the crowns or rhizomes of perennials, such as peonies and bearded iris, and on dry-climate perennials, such as thyme and creeping sedums. "This is one of the big problems in perennial gardens," he said. Better to use a gravel mulch. Viette likes crushed pea gravel; others favor chicken grit, which will retain soil moisture but keep crowns and foliage dry.

Bagged mulch is more expensive than a delivery of bulk mulch but is easier to handle and spread. And in small city gardens, bags may be the only way to haul mulch.

Bulk mulch is more likely to turn sour from being stored in a wet and airless state, causing the build up of compounds so acidic that they poison plants. Sour mulch smells bad, like rotten eggs or vinegar, but getting it returned once it is dumped in your driveway may prove a challenge. Perhaps you should take a whiff before it is unloaded. Mulch should smell earthy. Its color, increasingly, is a matter of choice.


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