Crabgrass is portrayed as the great American scourge. I suspect no other weed has been vilified in as many comics or satires as this one. To a gardener facing crabgrass problems in the lawn, it is definitely not a comedy.

Crabgrass is a warm-season, annual grass. Similar grasses include barnyard grass and foxtail. These grasses start growing in the spring when soil temperatures rise. They grow throughout the summer and die with the first frost. Therein lies their vulnerability and our ability to control them.Crabgrasses and related annual weeds are successfully controlled with pre-emergence herbicides. Pre-emergence herbicides are put down prior to germination. It is erroneously supposed that pre-emergence herbicides prevent weeds from growing up or kill weed seeds. They do neither. Pre-emergence herbicides are placed on the soil before the plants grow. They then form a barrier in the top layer of the soil. As weed seeds germinate, the tiny shoot contacts the barrier, and the shoot absorbs small amounts of the herbicide. The seeds are not affected until they begin to grow nor is the herbicide effective after the seedling emerges.

After crabgrass preventers are applied, don't disturb the barrier. Aeration, hand or power raking, and other operations must be completed prior to applying the herbicide. Disrupting the barrier by mechanical means can allow seeds to emerge. Pre-emergence herbicides are the perfect way to control these annual weeds.

If the weeds emerge, what is the solution? A number of postemergence crabgrass killers are on the market, but they do not work very well. They must be applied after the plants emerge. These include the arsenical products such as DSMA or MSMA.

One new herbicide that's very effective on postemergence crabgrass is Acclaim, which is a very expensive product and not available to homeowners, but many lawn care services apply this product. Again, it only works if the plants are small, so if you see crabgrass emerging after mid-April, you may want to use a lawn service.

Postemergence control of spurge is much more difficult. Most broadleaf weed killers list on the label that they control spurge. Unless they are sprayed on the spurge in the early part of June when the plants have only two or three leaflets, they are ineffective. Most people don't even notice the spurge plants until late July or August when they form a fast-growing network of low-growing vines across the surface of the grass.

Organic control of weeds includes good lawn maintenance practices. Adequate fertilizer and high mowing are both effective in discouraging these weeds. Crabgrass seeds need light and warm temperatures to germinate. They are not competitive and will not grow well with other grasses. Crabgrass usually comes in dead area in the lawn or along sidewalks where traffic or other problems suppress the growth of desirable grasses.

Crabgrass preventatives are applied by biological dates. It has been recommended for many years controls be applied when the forsythia blooms, but that is too early. A better biological date would be when the crab-apples bloom, particularly "Radiant" crab-apples. Applying pre-emergence herbicides too early is counterproductive, since most are only active for six weeks. If the application is made too early, seed continues to germinate after the herbicide loses effectiveness.

Grasscycling is a new name for an old way of caring for your lawn. Grasscycling is practice of leaving the clippings on the lawn. This is a radical change for some Utah gardeners, but it is the most ecologically sound way of managing turfgrass areas. Few large turfgrass areas, including city parks departments and universities, pick up grass clippings. It simply is too costly and is not needed. Grasscycling is a more natural way of caring for your lawn and reduces fertilizer use while improving the soil.

Contrary to popular opinion, clippings do not cause thatch. Thatch is composed of below-ground portions of the grass including the decaying roots and rhizomes. Clippings are mostly water and decompose rapidly in most situations. Leaving the clippings does not spread diseases, nor does it damage the lawn if the lawn is mowed frequently enough to avoid piles of clipping left on the lawn.

Generally any lawn mower can grasscycle, providing you keep the blade sharp and mow when the grass is dry. Presently, landscape waste, including grass clippings, account for about 20 percent of the curbside waste going to the landfill. Grasscycling helps prevent this waste of landfill space and of the valuable soil improving qualities of the decomposing grass clippings.

If you'd like to know more about grass-cycling, you can attend a grasscycling kick-off program on April 13 at the Salt Lake City Building, 400 S. State St. The public is invited. Future columns will provide additional information on grasscycling.

As part of County Government Week, Salt Lake County is offering free trash bags at any county fire station as long as they last. Drop by for a handful this week. The Salt Lake Valley Landfill is also offering no-fee dumping at its 6030 W. 1300 South location during April.

- Budding and grafting, April 16, Tuesday, County Government Center, 2001 S. State, S1007, 2-4 p.m. or 7-9 p.m. Learn techniques, $2 material fee. Preregistration requested. Call 468-3170.

- Larry Sagers is a horticulturist with the Utah State University Extension Service.