Researching Maintenance

Cocoa hulls I have been looking, without luck, for cocoa hull mulch. How can I find some?-Via the Internet

Because of its greater expense and shorter life, this material is better suited for use by gardeners, many of whom feel its soil enriching and aesthetic properties are worth the tradeoff. Check with retail nurseries, garden departments and the like. Though many do not carry this material, they're your best bet. Sooner or later, you'll probably run into some at a retail outlet.

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Cocoa hulls-the byproduct of cocoa beans processed to make chocolate-have higher nutrient content than wood or bark mulches and improve the underlying soil as they decompose. They also have a natural look and distinctive smell that many people find pleasing.

However, cocoa hulls are imported and usually available only in bags, so they are considerably more expensive than most mulches. Plus, they decompose after about one season. Therefore, using this material entails greater effort and expense-both short- and long-term-than conventional mulches. That's why commercial operators rarely use this material.

Fish bait I am looking for a material that you can pour onto a lawn to bring earthworms to the surface for harvesting. However, I have had no luck locating such a product.-Via the internet

Paul Backman, a researcher at Washington State University, has studied earthworms extensively and recommends a method developed by Dr. Catherine Fox, a Canadian researcher at the Southern Crop Protection and Food Research Centre (London, Ontario). In Backman's experience, Fox's method is effective and essentially harmless to the worms (in case you want to save them for fishing bait, for example, or return them to the soil). However, it is not practical for harvesting earthworms on a large scale, something that is currently not economically viable.

Fox recommends using a mixture of hot mustard powder and water. The resulting solution can be poured onto the ground to flush out the worms.

Use about 2 ounces of hot mustard powder (such as you'll find in a food store). A bit at a time, add about one-half cup of water to form a paste. Let this stand for at least 2 hours to allow the "heat" to develop in the paste. Then thoroughly mix the paste with 1.5 gallons of water.

At the site where you want to flush out earthworms, place a 2-foot-square wooden frame on the ground and bank soil against the outside edges to help it retain the liquid. Pour the mustard solution into the frame. Earthworms should begin to emerge within 1 to 2 minutes.

Fox advises wearing latex gloves when mixing and applying the mustard solution because some people's skin is sensitive to mustard.

For more detailed instructions on using this method to extract worms, visit http://res.agr.ca/lond/pmrc/faq/wormsoil.html.

Fall fertilization What is the current view on fall fertilization of trees and shrubs?-Kentucky (via the internet)

The answer involves several issues. What concerns many horticulturists most is that a late-season application of nitrogen might trigger a flush of growth that would make the plant more susceptible to winter injury. That's why many withhold all but the mildest fall applications.

Dr. Stuart Warren, a woody-plant specialist at North Carolina State University, feels that fall is as good a time as any to fertilize trees and shrubs if you adhere to typical rates-that is, avoid heavy applications.

Warren notes that the timing of a fall application is important as well. In North Carolina, "fall fertilization" means late September or early October. In more northern regions, the schedule should be moved up accordingly. If you fertilize too early, the plant may be in a physiological state that could allow new growth. Conversely, the application should be early enough that the leaves are still photosynthetically active. If they are preparing to drop, little nutrient uptake will occur and the application will have been largely wasted.

Fall may be a safe time to fertilize, but is it the most effective time to fertilize? That, according to Warren, is difficult to answer, though it is receiving more attention lately. Warren conducted research on red maples and found that it didn't seem to matter whether the applications took place in spring or fall. Further, while fertilized trees performed much better than their unfertilized counterparts, rates up to 6 pounds of nitrogen per 1,000 square feet produced no more growth than a more-modest 2 pounds.

A modern dogma of the landscape industry is that xeriphytic plants reduce water use. This is repeated so often that few stop to consider that using drought-tolerant plants is only half of the solution. After all, xeriphytic plants reduce only the need for water. The other, more difficult, part is changing people's irrigation practices so that they actually apply less.

Many cities, particularly in the arid Southwest, provide incentives for converting conventional landscapes to xeriscapes. Similarly, homeowner and community associations frequently enact rules to promote or require the use of xeriphytic plants. Residents are told that xeriscaping can reduce landscape water use up to 50 percent compared with a similar-sized bermudagrass lawn. But does this savings actually occur?

Researchers at Arizona State University recently tested that assumption. One reason to call it into question is the fact that while xeriphytic plants tolerate drought, many also can use copious amounts of water if it is available. For example, the researchers note that blue palo verde and mesquite often use more water in irrigated landscapes than Chinese elm trees. The key to saving water with xeriscapes, therefore, is not only using the right kinds of plants; it's also cutting back on your irrigation.

To determine whether differences in water use existed between xeriscapes and conventional landscapes, the investigators retrofitted water meters to irrigation systems in both types of landscapes. Surprisingly, they found that the xeriscaped sites consistently used more water than the "mesic" sites, not less.

To illustrate how xeriscaping can fail to conserve water, the researchers compared two xeriscaped residences. Both used similar plants (creosote, acacia, palo verde, etc.) and were devoid of turf. However, one residence used 1.2 gallons per square foot, while the other applied 9.9 gallons per square foot. The yearly water-use difference between the two would amount to about 218,000 gallons. Despite this, there were no visible differences in plant appearance or health.

As part of their study, the researchers surveyed Arizona homeowners about their attitudes regarding landscapes and irrigation habits. The results help explain the water-use patterns of xeriscaped residences. Most homeowners do not want a "desert" in their yards. Rather, they prefer more of an "oasis," with at least some areas where plants appear lush and vigorous. Thus, residents install xeriphytic plants, as they are often told to do, and then tend to overwater the entire landscape to promote growth and vigor.

This study illustrates the need for better educating the public about irrigation practices, which would help xeriscapes fulfill their intended purpose of reduced water use.

However, it also reveals that the push for strictly xeric landscapes goes against the preferences of many homeowners. Alternatively, designs that incorporate largely or entirely unirrigated areas with a few "oases" to add some greenery-a strategy some experts already recommend-would help satisfy homeowners as well as reduce water consumption.

Little more than a year ago, the University of Maryland's Dr. Peter Dernoeden and some colleagues described a new turfgrass disease-bentgrass dead spot (BDS). Since that time, the disease has been identified in several East Coast states.

The initial symptoms include small purple-red clusters of leaves, creating 1- to 3-inch reddish spots on putting greens. The outer leaves remain purplish in color and eventually produce a 0.5-inch diameter "halo" that helps distinguish this disease from ball marks and other diseases. No mycelium is visible on dewy mornings as it is with dollar spot.

The BDS fungus-Ophiosphaerella agrostis-is related to certain pathogens associated with spring dead spot and necrotic ring spot. However, this particular fungus was previously unknown.

It infects leaf sheaths, crowns and roots, and seems to be most active in spring and fall.

Curiously, BDS seems to be more common on greens that receive good light and air circulation. Further, it often occurs on 3-year-old greens constructed to USGA specifications.

Currently, no fungicides have labeling for BDS. However, North Carolina State's Dr. Henry Wetzel has found the high label rates of Daconil Ultrex, Cleary's 3336, Consyst and Spectro provide good suppression.

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