Wood chips in vegetable garden will rob soil of vital nitrogen


May 30, 1999

Q. Is it OK to use wood chips in my new vegetable garden?

A. No, stay away from wood chips. They can damage tender plant stems and they will rob your soil of nitrogen. Microbes in the soil will use up available nitrogen for protein synthesis as they break down the cellulose in the wood. Select other types of organic mulches for your garden, such as grass clippings, newspaper covered with straw, or leaf mold.

Q. My beautiful climbing rose was attacked by some type of insect (I suspect gypsy moth) while I was away on vacation. The leaves are all half-eaten. Will my plant grow new leaves?

A. The gypsy moth is innocent. Your rose was visited by the bristly rose slug, a common type of sawfly. The slender, green- yellow larvae skeletonize the leaves. You can pick them off the undersides of the leaves, but wear gloves because they can irritate your skin. The slugs can also be controlled with insecticidal soap or horticultural oil.

Your plant will grow out of the damage. Fortunately, there is only one generation of bristly rose slug each year.

Q. The leaves and twigs at the ends of the branches of my 7-year-old Bradford pear trees are turning black. I grew up on an apple farm and I know that what I'm seeing is not fire blight. Is there some other disease that is causing this? What can I do about it?

A. The same symptoms were observed widely in the spring of 1998, after the severe drought of 1997. Your trees probably have been drought-stressed for the past two years. They expended their limited stored food reserves this spring, producing flowers, foliage and shoots. Terminal dieback occurs in this situation because trees are unable to support the new growth.

Water your trees deeply and regularly during drought, and prune out the dead terminals.


1. Put tropical lilies out in backyard ponds. Most varieties require a minimum of five to six hours of sunlight each day.

2. Construct and install stakes, trellises and cages for supporting tall flower and vegetable plants. Waiting too long could mean damage to newly emerging plant roots.

3. Pinch the flower buds of mums and asters to prevent early flowering.

4. Head back first-year raspberry and blackberry canes to 3 feet from the ground to encourage the growth of laterals. Keep laterals pruned to 18 inches.

Garden tips are provided by the Home and Garden Information Center of the Cooperative Extension Service of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at www.agnr.umd.edu/users/hgic.

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