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Mulch has many benefits, so lay it on thick

Mulch is so much more than a finishing touch in landscaping. It reduces labor by controlling weeds, slowing evaporation and enriching the soil, to name just a few of its benefits.


Mulch is so much more than a finishing touch in landscaping. It reduces labor by controlling weeds, slowing evaporation and enriching the soil, to name just a few of its benefits.

I'm fond of saying that there are three things you can do to eliminate 95 percent of your gardening challenges. First, put the right plant in the right place. Second, improve the soil by adding plenty of compost and organic matter. Third, add mulch. • Of all the ways I can suggest to save time and work in our landscapes and gardens, the generous use of mulch is a key component for allowing that to happen. Here are some of the main ways mulch gives back so much.

Joe Lamp'l, Scripps Howard News Service

Suppresses weeds

One of the most loathed tasks for any gardener or weekend warrior is weeding. Although mulch won't guarantee a weed-free landscape, it does greatly suppress seed germination by blocking sunlight to the soil surface — an important ingredient many weed seeds need to germinate. Unfortunately, weeds are weeds, partly because of their ability to sprout and grow in the most challenging conditions. Birds, wind, pets and people will always be couriers of weed seeds, so they'll still sprout in your mulch. But when they do, they're easier to pull out since much of their roots are in the loose top layer of mulch.

Retains moisture

You don't need to be a horticulturist to know just how quickly exposed soil surfaces can dry out in the hot sun. Over time, moisture below the surface evaporates. Unfortunately, many roots suffer from the dehydrating effects of exposed surfaces. A 3-inch or so layer of mulch acts to provide a protective, insulating barrier from the evaporative effects of the sun and heat, holding in precious moisture far longer and deeper than exposed surfaces.

Reduces plant disease

Many disease pathogens reside in soil and can easily be splashed up onto plant foliage, which can then become infected. Mulch reduces the chance of this happening by providing a protective layer, blocking the splashing of pathogens onto stems and leaves.

Moderates soil temperatures

Similarly, that same layer of mulch moderates soil temperatures by helping keep it cooler in summer and warmer in winter. Think of mulch as a thermal insulating blanket. Having a generous layer of mulch around plants and trees can literally make the difference between life and death when it comes to extreme temperatures in summer and winter.

Improves soil

Any natural mulch will break down and decompose in a relatively timely manner. As it does, it improves the existing soil with important organic matter, a vital ingredient to sustaining soil quality and nutrients.

Buyer beware

Unfortunately, decomposing mulch can also add material you would never want in your soil. This includes substances such as arsenic, from pressure-treated wood. Play it safe with the mulch or soil you buy and look for the certification seal from the Mulch and Soil Council on approved bags. It ensures that the product you are buying is free of unacceptable chemical materials. (I almost learned about contaminated mulch the hard way when I nearly purchased a load containing old pressure-treated wood. As an eco-friendly gardener and a father, I never would have knowingly made such a purchase. I believe so strongly in this message that I became a compensated spokesman for the Mulch and Soil Council in 2007.)

In Pinellas County, free recycled mulch is available. It undergoes a natural sterilization process prescribed by the University of Florida's Institute of Food and Agricultural Sciences. Learn more at Type "mulch" in the search box.

Aesthetically pleasing

Finally, there is no denying the eye-pleasing appeal that mulch adds to any landscaped bed. On top of the valuable benefits mulch offers to the health of plants, a generous layer of mulch adds the finishing touch that complements and sets off your landscape or garden beautifully.

Joe Lamp'l, host of "GardenSMART" on PBS, is a master gardener and author. Contact him through

Mulch math

Mulch is often sold by the cubic foot, which might leave you guessing how much you'll need for your yard. Here's a formula to help you figure it out:

• Determine the square footage of the area you want to cover. For example, for a 4-by 25-foot bed, you would multiply 4 by 25. You would need to cover 100 square feet.

• Multiply the depth of the mulch by the area to be covered. Three inches, or .25 of a foot, is a good depth. In our example, we would then multiply 100 square feet by .25, for an answer of 25 cubic feet of mulch.

• Bags of mulch are typically sold in quantities of 2 cubic feet, so to determine how many bags to buy, divide the total mulch needed by 2. In our example, we would divide 25 by 2, for a total of 12.5. We would then pick up 13 bags of mulch.

Source: Hillsborough County Extension (

Types of mulch

There are many types of organic mulches, which you can buy by the bag or the truckload. The most common retail mulches are pine bark, pine straw/needles, eucalyptus and cypress. Other, less common mulches are melaleuca, compost and recycled utility mulch.

Some organic mulch can be found right in your own yard: grass clippings, oak leaves and pine needles make great mulch. Grass clippings, if left on the lawn after mowing, will decompose and return nutrients back to the lawn, contributing as much as 1/2 pound of nitrogen in a year.

Here are some typical mulches

(some are more easily found than others):

Cypress: While this mulch is commonly found at garden centers, some people avoid using it in an effort to preserve cypress wetlands. (Cypress trees do not regenerate quickly.)

Eucalyptus: This light, reddish-brown mulch is produced from Florida plantations and settles minimally over time.

Melaleuca (Punk Tree): This mulch is made from an invasive exotic and has a high termite resistance with almost no settling over time.

Pine bark: This timber industry by-product

has good color retention, though large pieces tend to float away.

Pine straw: Another timber industry by-product (if purchased) or free (if from your yard or your neighbor's), it settles quickly.

Yard waste mulch: You'll have a variety of species in this mulch, and color and size may vary.

Source: Hillsborough County Extension (

Mulch has many benefits, so lay it on thick 08/14/09 [Last modified: Friday, August 14, 2009 4:30am]
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