Researching Maintenance

Mulch for turf establishment Which mulch is best for using over grass seed? I am now trying grass clippings. Is this effective or hurting my germination rates? - Virginia

For several reasons, grass clippings are not likely to be effective as mulching material for this use. The purpose of mulching is to prevent desiccation of germinating seedlings and to protect against soil erosion and movement of seed during heavy rains while still allowing enough air exchange to aid the germinating seed. Grass clippings do not satisfy all of these requirements.

Dr. Peter Landschoot, a turfgrass specialist with the Pennsylvania State University, explains that you would have to apply grass clippings in a thick layer to provide protection from desiccation and stabilize the soil and seed. However, doing so would create poor air exchange and smother the new seedlings. Further, clippings decompose easily and tend to rot quickly, producing a favorable environment for disease-causing fungi and a buildup of heat. To avoid these problems, you would have to apply clippings in a thin layer, but this would probably provide inadequate seed-bed protection. Plus, if the clippings dried out, strong winds could easily blow them about. Landschoot also suggests that clippings could be a source of weed seeds.

Straw is the most widely used mulch for newly seeded lawns and usually works well for this purpose. Straw, too, is not without its drawbacks - it may contain weed seed, so try to locate the cleanest straw possible. Plus, it sometimes is necessary, on slopes or in windy areas, for example, to use a binding agent or twine to keep the straw in place. Nevertheless, straw usually works quite well and is relatively inexpensive.

For slopes, you can use burlap, cheesecloth, jute or some other rolled material to minimize erosion. Other possibilities include excelsior or synthetic mulches that contain paper byproducts or wood-derived cellulose. Some of these are available for use in hydraulic seeders or in other forms such as pellets for ease of application. Though all synthetic mulches have advantages - for example, they usually are free of weed seed and may be available with charges of starter fertilizer - they also tend to be more expensive than straw. As you can see, a range of products is available for this purpose. While no perfect mulch exists, Landschoot suggests that grass clippings are a poor choice compared to other available products.

Fruit without flowers? A friend of mine has a fig tree that produces fruit, even though he's never seen it flower. He thinks that figs don't produce flowers at all, but I think they may just be inconspicuous. Who's right? - Washington

You are. In the case of edible figs (Ficus carica), the tiny flowers actually are on the inside of the fig. The fig itself, anatomically speaking, is a receptacle - the structure to which the flowers attach. The small seeds within figs develop from these fertilized flowers and are the true fruits. This seems like a strange arrangement, but it is not unique. For example, strawberries also are receptacles. The small seeds on the outer surface are its true fruits. Figs are similar, except that the receptacle is "inside out," in a way, placing the seeds on the inside. This configuration makes it seem like many other "normal" fruits, even though it is fundamentally different from them.

By definition, plants cannot produce true fruits without flowering, even though some will proceed to grow fruit even if the flowers haven't been pollinated. This is the case with figs, although certain varieties, especially some commercial types, require pollination from a minute wasp (and a male pollinator tree known as a caprifig) for the fig to develop into an edible state. Because this requires special steps (and knowledge of figs), your friend's tree apparently is one of the varieties that form edible fruit without needing pollination. Anyone who intends to plant an edible fig should ensure they plant one of the varieties that does not require pollination to produce edible "fruit." Nurseries typically stock these types, but double check anyway.

The Invasive Weed Awareness Coalition (IWAC) recently unveiled a national strategy aimed at controlling invasive non-native plants in the United States. IWAC consists of members from government agencies, businesses and non-profit organizations who are concerned about the destructiveness of invasive alien plants. The plan - Pulling Together, National Strategy for Invasive Plant Management - is a program promoting prevention, control and restoration strategies to combat these aliens.

A recent release from IWAC provides some alarming figures about invasive alien weeds: Estimates place the infested area at around 100 million acres, with an annual increase of 8 to 20 percent. Direct control costs for noxious weeds are estimated to be between $3.6 and $5.4 billion annually. Loss of agricultural productivity due to invasive weeds is pegged at around $7.4 billion. States with active programs for detecting new weeds find an average of nine species a year. Unfortunately, the typical "new" weed already has been present for 30 years and covers 30,000 acres before it is reported. Thus, current levels of detection are poor. Thousands of alien species have become established in the United States. About 1,400 of them are considered pests, and 94 are classified as noxious weeds.

The problem affects more than just agriculture, however: Waterways have become clogged, affecting fishermen and boaters. Many invasive plants are toxic, posing health threats to humans and livestock. Alien species often quickly dominate natural ecosystems, out-competing native plants and eliminating habitat for animal species.

Lest anyone think that invasive alien weeds have little impact on the turf and ornamental industry, consider that kudzu, purple loosestrife, star thistle, Japanese honeysuckle, kikuyugrass (see "Kikuyugrass revisited," at left), water hyacinth and musk thistle - all difficult weeds in their respective ranges - are alien species.

By encouraging research, education and partnership, IWAC hopes to "turn the tide" against these aggressive alien weeds. You can obtain a copy of the full report on the internet at: For a hard copy, you can call Kniffy Hamilton at (406) 255-2927 or write to her at: Granite Tower, P.O. Box 36800, 22 N. 32nd St., Billings, MT 59101.

Kikuyugrass revisited Joe Finger, a golf-course architect from Kerrville, Texas, wrote to Grounds Maintenance in response to Stephen Cockerham's recent article on kikuyugrass in California (May 1997). He implores: "Please let the public east of the Rockies areas of rainfall from about 20 inches up, kikuyugrass becomes unmanageable and a horrible nightmare." Referring to crews he has observed on golf courses in Mexico, Finger explains that they "keep it out of greens by hand picking and trenching around the periphery of the putting surface. But in the rainy season, they have to cut it every keep it from growing 2 or 3 inches. When they fail to mow it for 2 or 3 days, kikuyugrass becomes so high that when it finally is cut, it is so stemmy that balls sit on top. When it grows fast in rainy areas, it also gets a fungal disease that kills large patches and becomes unsightly."

Finger concludes by stating that many years ago, he asked the USDA to quarantine kikuyugrass to the West Coast, fearing that someone would intentionally bring this pest east. It's worth reiterating - as Cockerham noted in his article - that kikuyugrass is classified as a noxious weed. That means you cannot transport or plant it without a permit. It's also worth noting that Cockerham did not suggest intentionally planting kikuyugrass (a foolish thing by all accounts). Instead, he merely was suggesting finding a way to live with a pest you apparently have little chance of eliminating.

Interest always exists in finding uses for industrial byproducts. Here are two studies that demonstrate how our industry can use wood byproducts - sawdust and paper sludge - in turf establishment.

Sawdust. Sawmills generate large quantities of sawdust, much of which goes unused. In fact, large piles often sit for years, resisting decomposition due to extremely high carbon-to-nitrogen ratios. However, researchers at the University of Missouri discovered that composting sawdust (primarily oak) with poultry manure resulted in a product similar to peat. Could this be put to good cultural use?

To find out, the investigators applied 2 inches of sawdust composted with poultry manure to some study plots and uncomposted sawdust to others. They also added enough ammonium nitrate to the plots with uncomposted sawdust to keep the nitrogen levels similar in both treatments. Other plots with no amendments served as experimental controls. The researchers tilled all plots to a depth of 4 inches, limed and fertilized them and then seeded them with Kentucky bluegrass. This took place in October 1994.

Within a month, it was apparent that the performance of the Kentucky bluegrass in plots amended with uncomposted sawdust was less than that of the compost-amended and control plots. The turf in the uncomposted-sawdust plots was much thinner and was 20 percent shorter than turf in the check plots or those receiving other treatments.

By May 1996, differences were even clearer. Rating density on a scale of 1 to 10, the researchers ranked the turf in the uncomposted-sawdust plots at 5.5 and at 6.3 in the control plots. The compost-amended plots ranked highest, with a rating of 8.0. They also had fewer weeds and darker color.

This study demonstrates that composted sawdust can be beneficial for turf establishment. Conversely, uncomposted sawdust leads to poor results and can produce nitrogen-deficiency symptoms. The researchers note that some of the sawdust samples came from 20-year-old piles and still produced nitrogen deficiency in turfgrass seedlings, in spite of adding supplemental nitrogen.

Paper sludge. Researchers in Quebec conducted a study with the same basic aim - to determine the suitability of an industrial byproduct as a soil amendment for turfgrass establishment. This was a more complex study than the Missouri experiment, but results were similar.

In the Quebec study, the investigators used primary (residual virgin wood fibers) and de-inked (recycled) sludge, both of which are byproducts of paper mills. They mixed the sludges with various proportions of sand and organic soil and used the mixes as soil amendments. They then applied 6-inch layers of this mix to native soil and tilled it in to a depth of about 12 inches. The researchers subsequently established Kentucky bluegrass in the plots, using a variety of pre- and post-establishment fertilizer treatments (nitrogen, potassium and phosphorus). They rated the resulting turfgrass quality by visual assessment and percent cover.

As with most wood products, the main components of paper sludge are lignin and cellulose. Consequently, they suffer from high carbon-to-nitrogen ratios. Thus, it is not surprising that plots receiving supplemental fertility displayed "dramatically improved" quality. The researchers concluded that, with supplemental fertilizer, paper sludge can be an effective soil amendment.

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