Rhododendron roots could rot in wet, poorly drained soil

Backyard Q&A

In the Garden

November 23, 2003|By Dennis Bishop | Dennis Bishop,Special to the Sun

We planted seven rhododendrons two years ago. They made it through last year's drought, but now four of the plants seem to be dying. We have kept them mulched and watered. What might cause this?

Rhododendrons grow naturally on the slopes of hills and mountains in organic soils. They are generally mixed with trees and grow best in filtered light or partial shade. If your property has conditions such as these, you should be able to grow rhododendrons. If not, you may have problems.

While rhododendrons do not have to be planted on a slope, they require well-drained soil and should not be planted in low-lying areas or heavy clay. In wet, heavy soils they are very susceptible to phytophthora root rot. The fungal disease destroys plant roots and eventually kills the entire plant. I would suggest that you carefully dig up one of your damaged plants and examine the roots. If the roots appear to be rotting, this is the most probable cause.

Unfortunately, this disease is very difficult to control under these conditions. You will need to remove the plants and plant something else. Do not replace them with yew, cherry laurel, boxwood or juniper. They are also susceptible to the disease. If the roots appear healthy, please call the Home and Garden Information Center at the number below to get further assistance.

I just purchased three new trees for my yard, but I was surprised by the high cost. What makes trees so expensive?

Small trees are generally not expensive, so I will only comment on the cost of large trees. All large landscape trees started off small and have been cared for by a wholesale nursery for a number of years.

Each year of care (pruning, watering, fertilizing, weeding) contributes to the cost. Large trees also have to be handled differently from small trees. They must be dug, balled, burlapped and caged in the field, and then brought in for shipping. Because the root balls are large and heavy, there is a significant shipping fee for each tree. Finally, every tree must be displayed for retail sale, provided with a guarantee and sold. Each of these items contributes to the cost. When it is all added up, the price of large tree seems very reasonable and the price of a small tree is a true bargain. Your new trees will grow in value every year and will greatly contribute to the resale value of your home.

Checklist

1. Patio plants like hibiscus and flowering maple will overwinter in your home. Place plants in a bright window and keep them watered through the winter.

2. Check all bulbs before planting. They should be solid and firm. Soft bulbs may be diseased and should be discarded.

3. This is a good time to transplant shrubs and small trees. Be sure to dig carefully to preserve the roots.

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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