This year's new growth of liriope should reveal the cause of last year's disturbing brown leaves

Backyard Q&A

April 27, 2003|By Dennis Bishop | By Dennis Bishop,Special to the Sun

Late last summer, the leaves of my liriope plants began turning brown, and I was concerned that they were dying. Was this due to the drought, or could there be another cause?

The drought may have damaged your liriope, or you may have a disease called liriope anthracnose. If drought was the problem, I would suggest that you cut out all the damaged foliage and allow the plants to recover this spring. They should put out a nice flush of growth and look like new. If disease were the problem, I would do the same thing, but be prepared for the disease to return this summer.

Liriope anthracnose causes the tips and margins of leaves to turn brown. The best way to limit this disease is to keep your plants healthy and avoid overhead watering. Liriope grows best in well-drained soil that has been supplemented with ample organic matter. It is best planted in partial shade. When grown in less than ideal conditions, the plants will be weaker and more susceptible to the disease.

In a column you wrote last year, you mentioned a new treated lumber called ACQ.

Can you tell me more about this lumber and its use in the garden?

ACQ (alkaline copper quat) is a chemical that is now being used to treat lumber. Some manufacturers are using it in the same way that CCA (chromated copper arsenic) has been used to pressure-treat lumber.

ACQ was developed amid increasing concerns over the use of arsenic in CCA-treated lumber. Arsenic is a known carcinogen, and research has shown that it leaches from the wood and can contaminate soil. Arsenic can also be picked up on the skin when the wood is touched or handled.

Because ACQ does not contain arsenic, it is purported to be safer for use in the garden. It is available through some local lumberyards; however, it may require a special order. It will cost 20-25 percent more than CCA-treated lumber.

If you would like to build raised beds, a deck, or play equipment, ACQ lumber seems to be a good alternative. Given that the EPA is banning the use of CCA-treated lumber for most residential purposes, it may be your only alternative in the coming years.

Checklist

1. Tender annuals like petunias, peppers and tomatoes can be protected from late frosts with paper bags, cardboard boxes or 1-gallon milk jugs.

2. Thin out carrot, radish, turnip, lettuce and spinach seedlings from beds where seed was sown thickly. Thickly grown plants will not be productive.

3. If you observe leaf spot diseases on mature ash, hickory, maple, sycamore and oak trees, do not spray. They are not harmed by these diseases.

Dennis Bishop is an urban horticulture educator for the Baltimore office of the Maryland Cooperative Extension Services. If you have a gardening or pest problem, you can call the Home and Garden Information Center hot line (Monday through Friday, 8 a.m. to 1 p.m.) at 800-342-2507. You can also e-mail questions, order publications and diagnose plant problems by visiting the Web site www.hgic.umd.edu.

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