---

This is the time of the year when homeowners turn their attention to lawn care. It's soon time to renovate, seed, and fertilize. It's also the time of year to begin a weed control program.

Weeds are plants out of place. A plant may be desirable in one situation and a weed in another. Weeds detract from the beauty of lawns due to the contrast in color and texture between the desired grass plants and the weeds. In addition, weeds compete with the desired grass plants for available water and nutrients, usually resulting in thinning of desirable plant cover.

Lawn weeds may be divided into two classes based on the way in which they emerge from seed.

Monocots emerge with a single seed leaf where as dicots emerge with two seed leaves. Most monocot weeds found in turf grass are termed weedy grasses. Examples include crabgrass, annual bluegrass, tall fescue and quack grass.

Dicots, on the other hand, is the term for broadleaf weeds and include such plants as dandelion, clover, ground ivy (creeping charlie), knot weed and plantain.

Weedy grasses and broadleaf weeds are further divided into groups according to the plants length of life. Perennial weeds have a life of more than two years, though new seeds may be produced every year. Biennial weeds have a life of two years, generally storing up food reserve in the leaves and roots the first year and producing seed in the second year.

The biennial weeds often are grouped with perennial weeds since control is similar. Annual weeds germinate from seed, grow, flower, and produce seed in less than one year. Summer annuals germinate in the spring and mature in the fall, and winter annuals germinate in fall or late winter and mature in late spring.

The most effective method of controlling lawn weeds is to maintain a dense and vigorously growing turf cover. Weeds are often an indication of problems in the grass plant environment and killing the weeds without correcting the underlying problem will lead to unsatisfactory results.

A combination of proper cultural practices plus prudent use of chemicals is sometimes necessary to control weeds effectively in turf. Whenever herbicides are used, container labels should always be read and followed carefully.

Pre-emergent herbicides affect germinating seeds. To be effective, these chemicals should be watered into the ground two weeks before you expect crabgrass seeds to sprout. The best time is usually late April or early May. (Typically, crabgrass sprouts around Memorial Day in the Twin Cities area.)

For serious crabgrass problems, apply pre-emergent herbicide a couple of weeks earlier to "hot spots" along curbs, sidewalks, and driveways, and sunny, south-facing, slopes. Do the rest of the yard in early May. Then repeat the application again the second or third week of June.

Crabgrass does not all sprout at once, so it might still be worthwhile to apply a pre-emergent herbicide even after a little crabgrass has begun to show up. It won't damage the plants that are already visible, but will prevent more from sprouting.

Crabgrass is an annual, meaning the roots do not survive from one year to the next. Instead, new seedlings sprout each year from seeds left behind during past growing seasons. There are many different pre-emergent herbicides formulated for home use. Only one pre-emergent chemical, siduron (also called Tupersan) can discriminate between new grass seed and the crabgrass seed. Siduron is the active ingredient in several products including Scott's Starter Fertilizer Plus Halts. These products should be used if you are planning to plant grass seed and need to be watered into the soil after you've planted your grass seed.

Post emergence herbicides are used to kill weeds after the weed plants are up and growing. To be effective, most post emergence herbicides must be absorbed through the leaves. Therefore, liquid sprays generally work better than a dry, granular material. However, granular may be the most practical way for homeowners to apply these materials

Selective post emergence herbicides are usually used to control annual, biennial, and perennial broad-leaved weeds because they will kill many broadleaf plants without damaging grasses plants. These herbicides can severely damage or kill tress, shrubs, and flowers, so they should be used with great care near these plants.

Post emergence herbicides may be applied any time the weed is actively growing and the air temperature is between 60 degrees and 80 degrees. There should be no wind and no rain in the forecast for 48 hours. Most effective control of perennial broadleaf weeds is obtained when applied in early fall between August 15 and October 15. If applied in the spring, it should be between May 1 and June 1. These products are not very effective during our typical hot July weather.

Some resources for more information:

www.extension.umn.edu/proj ects/yardandgarden/ygbriefs/h506crabgrass.html

www.extension.umn.edu/infou/plants/BG531.html

w.extension.umn.edu/distribtion/horticulture/DG1137.html

+++++

The next classes in our 'Garden Fever' series are:

Saturday, April 28 -- Organic Gardening Methods, Improving your Soil, and Beneficial Insects

May 1 -- Michelle Grabowski, Regional Extension Educator, will talk about using organic and low-impact disease control methods in your yard and garden.

Class brochures as well as the plant order forms are available on the website at www.extension.umn. edu/county/chisago or you can call the Extension office at 651-674-4417 to have one mailed to you.

A cutback in staffing has made it necessary for the Extension Office to limit hours of operation. At present, the office will be open on Tuesdays and Thursdays. We would suggest that you call ahead to verify that the office is open before you stop by.

+++++

We still have some bare root plants for sale although we are running low on some varieties. Due to the office hours at the Extension Office in North Branch being reduced, some requests for information may be delayed. Therefore, I do not mind if you call me at my home regarding plant orders or class offerings. My number is 651-257-4496.

---