Chemicals & Horticulture

Tennis, anyone? I am seeking information regarding the maintenance of grass tennis courts. Can you point me in the right direction?--Address unknown (via the internet)

Similar to golf greens, grass tennis courts are constructed with a gravel base and drain tiling. However, instead of a sand-based root-zone medium such as you'd use for a golf green, the turf grows in a clay-loam mix to provide a firmer surface than you could obtain from a sand-based medium.

Grass tennis courts require most of the typical practices--mowing, irrigating, fertilizing, controlling disease, aerating, topdressing, etc.--but with unique variations. Tennis-court mowing heights range from 0.25 to 0.75 inch, depending on the playing characteristics you seek (shorter turf provides a faster game). The turf species you select depends on the climatic zone you're in and the mowing height you intend to use.

An annual fall renovation is standard practice for many grass courts, involving aerating, dethatching, topdressing and reseeding. Then, turf can recuperate until play resumes in spring. Such a practice is necessary because grass tennis courts can become badly worn after a season's play.

The U.S. Tennis Association (USTA) and the U.S. Tennis Court and Track Builders Association publish a book, Tennis Court Construction and Maintenance, that provides detailed information on grass tennis-court maintenance and construction. Call the USTA at (914) 696-7000 for more information.

Pruning azaleas I am doing some heavy pruning on older azaleas. Should I push some new growth with fertilizer before fall to ensure good flowering?--Maryland

Many references suggest withholding fertilizer from azaleas after August. Although some experts overstate the danger presented by late-season fertilization, it still is a valid concern, and August is a good cut-off date. Further, it is probably not necessary to add more fertilizer than normal to push new growth. If you already have your plants on a good fertility program, they should possess adequate resources to do so.

Your question shows you are aware that azaleas flower on newer growth. This being the case, spring generally is the best time to prune, just after bloom. However, some types require particular timing for best results. Therefore, I recommend consulting a reference on azaleas for variety-specific information.

Many azaleas require little pruning, and you can typically reach your shaping goals by clipping out small branches--not the kind of thing that would result in a heavy flush of growth. However, some people prune old, leggy specimens nearly to the ground for "rejuvenation." This questionable practice often succeeds but also poses some risks. Not all varieties respond to severe pruning with new growth--some simply die. Look for small shoots at the base of the larger branches. If present, it's likely the plant will recover with new growth. If you see none, you would be wise to first cut back just a few branches to see how they respond before cutting all of your shrubs back.

Humic substances are important chemical constituents of humus, long recognized as a highly beneficial component of soil. Humic products marketed for turfgrass use have become more common in the last several years, and superintendents have reported improved summer stress tolerance in bentgrass, among other benefits, from their use. However, although researchers have confirmed the positive effects of humic substances on other grasses (such as cereal crops), few studies have looked at their effects on turfgrass. Therefore, researchers at North Carolina State University conducted an experiment to clarify whether bentgrass can benefit from humic substances as research has shown other crops to and as anecdotal reports suggest.

Using hydroponically grown 'Crenshaw' bentgrass plugs, the researchers added various concentrations of humic acid to the growth solutions. They then measured its effects on photosynthesis, chlorophyll content, root dehydrogenase activity (a measure of root-tissue respiration), tissue-nutrient levels and root-mass regrowth of the bentgrass.

Although the effects of the humic acid were not dramatic, the researchers noted some positive results. At the highest concentration of humic acid (but not at lower concentrations), photosynthesis increased significantly. Chlorophyll content did not also increase, so the rise in photosynthetic activity was due to some factor other than more chlorophyll. At higher concentrations, the humic acid increased dehydrogenase activity and root-mass regrowth, though it had neutral or even negative effects at lower concentrations.

The researchers also found that the humic acid increased tissue levels of certain nutrients by small amounts. However, they suggest that the differences were too small to be "biologically significant." Therefore, the positive effects noted in this study were probably due to something other than direct nutritional factors. The researchers do note, however, that their growth solution contained ample nutrition. In field situations where nutrient availability often is much more limited, nutritional effects of humic substances may be much more pronounced. This, in addition to the greater root and photosynthetic activity seen in this study, may help explain the positive field reports resulting from the use of humic substances. Actual field studies would help further clarify humic substances' effects on turfgrass.

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