Soil meter is not precise

Garden Q&A

March 02, 1997

I'm thinking about buying a soil pH meter I saw advertised in a seed catalog. How accurate are they? Are they worth the money?

Typical soil pH testers have a set of probes that are inserted into the soil. They cost $20-$25 and may be accurate to within half a pH unit. For example, if your soil pH is 7.0, a meter may register a pH value between 6.5 and 7.5. The same is true of do-it-yourself soil tests that contain litmus paper or powders. With certain plants, such as azaleas, a reading that is off by half a pH unit can mean the difference between growing success and failure. Our recommendation is that you have your soil tested through the University of Maryland's Soil Testing Laboratory. For a $5 fee you will receive a report listing your soil pH, phosphate, potash and magnesium levels and a fertilizer and lime recommendation. This test only needs to be done every three to four years. Call the toll-free number listed at the end of this column to order a soil-testing kit.

I just moved into an old home. There are numerous boxwood bushes around. They have yellow foliage and look very unhealthy. What can I do to bring them back? And can I transplant some of them to other locations around the property?

Boxwoods are susceptible to a number of insect pests and diseases. The yellowed foliage may have resulted from boxwood leaf miners, boxwood mites, scale insects or boxwood psyllids. These are all pests that suck plant sap, causing leaves to look bleached out.

A fungal disease called volutella, exacerbated by high rainfall, was especially troublesome last summer and fall. During the growing season, the fungus produces very noticeable masses of salmon-colored spores on infected branches. This disease can cause considerable dieback in boxwoods.

This is a good time to prune out any damaged or dead branches in your hedges. If you're not sure what is alive or dead, just scrape the bark with a sharp knife and look for green tissue. Green is the sign of life. If your boxwoods are in serious decline, you would be better off cutting them down to within 4 inches of the ground. They will begin to regrow in the spring. Don't move these shrubs. They have fine, shallow roots; moving them will only cause further damage.

I've heard that creeping thyme releases a pleasant fragrance when walked on. I'd like to plant some around my pathways if that is so. Also, is creeping thyme the same kind of thyme you use for cooking?

There are at least nine or 10 species of thyme. Several varieties have small, low-growing leaves that creep along the ground when planted at the edge of a pathway. These low-growers do indeed release a fragrance when crushed. When you buy thyme plants, ask a knowledgeable salesperson to help you select the appropriate type. All of the creeping thyme plants can be used in the kitchen.

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.

Checklist

Keep birdbaths filled with clean water and continue to feed wild birds through the remaining weeks of winter.

Remove branches, twigs and bark thrown in the compost bin over the winter. It will take years for these woody materials to break down.

Evaluate the quality of your lawn-service company. If you're not happy with it, now is a good time to switch -- before the first service of the year.

Pub Date: 3/02/97

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