If azalea leaves are turning yellow, the soil might not be acid enough


I planted azaleas two springs ago. The first year the leaves were dark green, but last year they started to turn yellow shortly after flowering. Would a soil pH problem cause this?

Yes, that might be the case. Most azaleas like a soil pH between 4.5 and 6.0. When the pH is too high, they may suffer from iron chlorosis and turn pale yellow. If that is the problem, you should consider removing the azaleas and planting something else that tolerates a higher pH. Or, you could treat the soil with a soil acidifier, such as aluminum sulfate. This is not a one-time fix. You will need to treat the soil in coming years to maintain the lower pH.

But before you do anything, test your soil. If your soil pH is appropriate, you will need to look for other causes of the problem. For example, azalea lacewings are insects that feed on the underside of azalea leaves in summer and cause them to turn a creamy yellow color. You should look for evidence of them.

We would like to grow some grapes this year. Do you have any advice for getting started?

I have seen some very nice grapes in Baltimore. Grapes are considered easy to grow; however, they are susceptible to black rot disease, which will need to be managed. They grow best in deep, well-drained soil that is average or even slightly poor in fertility.

If the soil is too fertile, the plant will produce an abundance of foliage but few fruits. Be sure to start with clean, disease-free vines that have been grafted onto a disease-resistant rootstock.

Grapes can be planted in fall or spring in a sunny location, 6-8 feet apart on a trellis. Pruning is a very important part of grape production. Your vines will need to be trained on the trellis during the first two years, and will need to be thinned after that. Thinning will promote good air circulation and discourage disease.

Concord is still the standard table grape and is widely available through nurseries and mail-order catalogues; however, it is susceptible to black rot disease. Several varieties that exhibit some disease resistance are 'Canadice' (red), 'Himrod' (yellow) and 'Steuben' (blue). For more information on grapes and grape growing, please call the Home and Garden Information Center at the phone number below.


1. Lettuce seed can be directly sown outdoors or started indoors and transplanted out. Start seeds at two-week intervals to ensure a continuous supply of lettuce through early summer.

2. Avoid pruning maple trees this time of year. Because sap "runs" in maples during late winter, they will bleed profusely from pruning wounds.

3. When cleaning the yard, watch for emerging spring bulbs. The shoots can be damaged by rakes or by being stepped on.

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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