The ABCs of mulch

Don't know much about mulch? Here are some guidelines.

By Times and wire reports
Photos by Jim Damaske
© St. Petersburg Times
published April 12, 2003

You might not think much about mulch. Just buy it, apply it and let nature take its course, right?

Not exactly.

The notion that one mulch fits all is so 20th century. And judging from the varieties on the market, from cocoa shells to straw, your choices are substantially broader these days.

Mulch is basically a multifunctional soil covering. It's used to help control weeds, retain soil moisture by limiting evaporation into the surrounding air and provide an insulating layer to reduce soil temperature fluctuations.

It's important to remember that different areas in your garden and/or landscape have different needs. One area might benefit from organic matter; another might do fine with inorganic materials. You also need to factor in cost, durability and availability.

Here are a few other things to consider:

As beneficial as mulch can be, too much can be harmful. The spreading distance depends on the type of mulch. A general rule of thumb is to spread mulch 2 to 3 inches thick. (For example, 37 cubic yards of a bark mulch will cover a 100-square-foot area at 3 inches deep. For other types of mulch, rocks or stones, coverage may be more or less.)

It's best not to pile mulch against a tree trunk or the stems of plants because mulch can trap moisture, which leads to root rot, diseases and insect infestation.

"Citrus trees are a good example," said Opal Schallmo, urban horticulturist for the Pinellas County Cooperative Extension Service.

"Their bark is thin and easily damaged. A disease called phytophthora, or 'foot rot,' is just waiting to attack at the soil line. Mulch not only traps the moisture against the trunk, it also hides the damage until it is too late to save the tree."

SOME TYPES OF MULCH

Bark mulch

Cocoa shells

Cypress

Pine needles

Grass clippings

BARK MULCHES are the byproducts of pine, spruce, milled fir and Douglas fir. They can be shredded, chipped or chunked. Bark mulches are attractive, resistant to wind and retard weed growth. The commercial availability of bark mulches offers greater selections, but some bark mulches can be toxic to young plants. Suggested retail: $2.49-$2.89 for a 2-cubic-foot bag.

COCOA SHELLS are lightweight, easy to spread, retain moisture well, keep weeds down and smell great (the chocolaty aroma lasts about two to three weeks). Cocoa shells also do not deplete soil nitrogen in decomposition. A harmless mold may appear if the temperature is very high, but rain or watering will wash it away. Hershey's Cocoa Mulch can be obtained from local distributor Bill Dodson at (727) 647-8235 or through the Web site at www.wtdhersheyscocoamulch.com. Also Willow Tree Nursery at (727) 522-2594. Suggested retail: $8.95-$9.80 for a 2- or 3-cubic-foot bag.

CYPRESS is the most common mulch available to consumers and is easy to apply. Cypress mulch is made of lumber byproducts and trees, and some caution that its manufacture is causing depletion of cypress wetlands. Suggested retail: $1.49-$3 for a 2-cubic-foot bag.

PINE NEEDLES work well with acid-loving plants such as azaleas and gardenias. Pine needles decompose slowly, are light and airy, and are easy to spread. They can be difficult to find commercially, but they are abundant in nature.

STRAW from wheat, oats, alfalfa or barley is widely available at feed stores and is inexpensive. Straw is a good mulch for tomato plants, strawberries, basil and blackberries. On the down side, it can harbor rodents, contains weed seed that can germinate, is easily uprooted by wind and is highly flammable. Some feed stores may have straw available.

WOOD CHIPS are available in a variety of colors. They are attractive, durable and stay in place. It's important to make sure that the chips have not been chemically or pressure treated. Suggested retail: $2.29-$2.89 for a half-cubic-foot bag.

STONES, PEBBLES AND GRAVEL look good but are expensive. They are available in a variety of sizes and some colors. They are fire resistant and won't blow away. Moisture retention and weed control are fair. Suggested retail: $2.99-$3.49 for a half-cubic-foot bag.

YARD WASTE (GRASS CLIPPINGS, LEAVES) makes excellent mulch because it adds nutrients to the soil, and best of all, it's free. Some cities and Pinellas County offer free recycled mulch; you just pick it up. Check with your local county extension service for more information. Use grass clippings that do not contain weeds or that have gone to seed (do not use Bermuda or Zoysia grass because these cuttings can take root). Grass clippings decompose quickly, so reapplication is needed often. Leaves can be used year-round as mulch, but landscapes, perennial beds and bulbs benefit from the insulation they provide during fall and winter. Slugs can present a problem when leaves are used as mulch.

Related stories

Homes