Be neither a Santa nor a Scrooge with mulch

November 21, 2012 

My daughter says I am a Scrooge. She wants me to put up the Christmas tree -- now. Actually, she wanted it put up several weeks ago. It does little good to remind her that we have not finished Thanksgiving yet. She wants to see her tree, even though the rest of the family wants to celebrate Thanksgiving first.

Salespersons in the stores seem to have the same issue. Some are ready for Christmas to come while others are content to wait. This does not separate the population into “Scrooges” and “Santas.” It is just the way we are.

When it comes to mulching plants in the landscape, gardeners seem to have a similar problem. Some people love to add mulch. They realize the benefit it has on plant growth. But some people apply too much mulch, which causes problems. Then there are the “mulch Scrooges.” They will not mulch around plants. Some even rake up the fallen leaves (which would make a pretty good mulch), and then they fail to replace the leaves with another mulch. How can we reach a proper middle ground? How much mulch is too much or too little?

Mulches around plants improve root growth. Proper mulching reduces weed competition, moderates the soil temperature, keeps the soil more moist and reduces pests. Mulching around trees means no mowing over roots while ducking low branches.

Mulch should be applied between 2 and 4 inches deep. I recommend that finer mulches such as pine straw, mini bark nuggets and shredded wood be applied 2 to 3 inches deep. Coarse mulches such as larger wood chips, leaves and bark can be applied 3 to 4 inches deep. Apply mulch out to the farthest reaches of the branches. Pull the mulch back several inches from the trunk.

Tailor the mulch to the location. Areas that stay wet may need little or no mulch. Mulching these areas can make soils too wet for good root growth. Areas through which water flows probably need a finer mulch or a stone mulch. These mulches should stay in place better when water is moving through the area. Especially avoid large bark in these areas because bark floats well. A dry river bed is a good idea in areas with lots of water flow.

Consider leaving a bare area next to buildings. This may help reduce pests inside. There should be at least a 6 inch gap between the mulch and any untreated wood on a building or any siding. Termites can use mulch as a place to hide and then gain access to the house.

Why should we worry about applying too much mulch? ”If a little is good, a lot is better -- right?” With mulch as with other good things, too much of a good thing can be bad.

Plant roots must remain moist to grow well, but they also need oxygen. Mulches that are too thick reduce the oxygen level in the soil and damage roots. Even the base of the trunk needs to “breathe.” Never pile mulch against the base of trees and shrubs. This can cause the trunk to remain too wet and to lack the oxygen it needs. The trunk can be attacked by pests hiding in the mulch: fungi, rodents and insects. Since the problem with the tree is buried underneath the mulch, you will probably not notice until it is too late.

Wood mulches are especially prone to problems when applied too thickly. They can actually become infested with fungi that will “waterproof” the top of the mulch. This prevents water from penetrating the mulch and the roots underneath die for lack of water. Dig into your mulch beds to see if this is a problem.

As the leaves are falling, remember that they make a great, economical mulch. Instead of hauling leaves away, rake them into beds around the tree to provide the benefits of mulch without added expense.

This is also a good time of year to have your landscape company mulch around your trees. Landscape work generally slows slightly after the leaves are removed and a landscape company could give you an estimate for mulching around your plants. For more information on mulching, visit http://tinyurl.com/be2tj3v.

Willie Chance works with the University of Georgia Center for Urban Agriculture.

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