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Early November is the most effective time to control broadleaf weeds in lawns. But what exactly are broadleaf weeds?

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

Monocots emerge with a single-seed leaf and dicots emerge with two-seed leaves. Most monocot weeds found in turfgrass are from the family Gramineae and are termed weedy grasses. Examples include crabgrass, annual bluegrass, tall fescue and quackgrass.

Dicots, on the other hand, are termed broadleaf weeds and include plants such as dandelion, clover, ground ivy, knotweed, chickweed, henbit 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 food reserves 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, whereas winter annuals germinate in fall or late winter and mature in late spring.

Effective control of weeds in turf is based on correct identification. Many books and charts are available to help in identifying common lawn weeds, or you can bring your weed samples into the extension office for identification.

At this time of year, dandelions have produced a flush of new growth, and new plants have germinated. Also, the winter annual weeds such as henbit and chickweed have germinated and are now starting to be seen in those thin areas of turf.

These young plants are small and easily controlled with herbicides such as 2,4-D or combination products (Trimec, Weed-B-Gon, Weed-Out) that contain 2,4-D, MCPP and dicamba. Even established dandelions are more easily controlled now than in the spring because they are actively moving materials from the top portion of the plant to the roots. Herbicides will translocate to the roots as well and will kill the plant from the roots up.

Be sure to choose a day that is 50 degrees or higher. The better the weed is growing, the more weed killer will be moved from the leaves to the roots. Cold temperatures will slow or stop this process.

Weed Free Zone (also sold under the name of Speed Zone) is a relatively new herbicide and contains the three active ingredients mentioned above plus carfentrazone. It gives a quicker response than the other products and will work better when temperatures drop below 50 degrees.

Of course, the most effective method of controlling lawn weeds is to maintain a dense and vigorously growing turf cover. Weeds grow well in open spaces where there is minimal competition from turf grasses. With proper maintenance, you can help your lawn out-compete weeds for light, nutrients and water.

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.

For example, a problem with knotweed and this time of year, chickweed, is usually an indication of severe soil compaction. Control of these weeds without correction of the soil compaction will only lead to sparse soil cover until the area is again invaded by weeds that grow in compacted soil. If white clover is your problem, it might well be you are mowing too close.

Often turf weeds can be controlled by altering the cultural practices to favor the grass plants rather than the weeds. The cultural controls may include raising (or lowering) the mowing height, changing the frequency of mowing, lengthening (or shortening) the period between irrigations, increasing (or decreasing) the application of fertilizer or aerifying the soil. When a few weeds do appear, hand digging will save time and money and is certainly healthier for the environment than herbicide treatments.

Last but not least, I have to tell you, I am not a big fan of the Weed and Feed Mixes. With herbicides and fertilizers, it's all about timing your application, and the time for fertilizing doesn't always match the timing for weed control. Use of these products can sometimes lead to unnecessary herbicide applications. When using the liquid products you have much better control over where you are applying the application. You can spray only the weeds which then minimizes usage of herbicides.

Unfortunately, herbicides are being found in the water that flows through storm sewers, most of which empty into the nearest stream. If you use these products, make sure to keep them on the lawn, sweeping any on paved surfaces back into the grass. Also, read the label before use.

Contact Karen Neill, an agricultural extension agent with the N.C. Cooperative Extension Service, at 375-5876 or karen_neill@ncsu.edu