Several kinds of weeds common to lawns can be treated at this time of the year with considerable success. This includes chickweed, henbit, dandelion, plantain, ground ivy (creeping charlie) and crabgrass.

There is one thing to consider before attacking the weeds. If they are destroyed, will there be any vegetation left? The weeds are better than nothing, they are green and help prevent erosion. It is late in the season to try to seed a bluegrass lawn, but a good time to put down sod.

Chickweed is a low spreading plant 4 to 12 inches high with small smooth leaves somewhat pointed at the tips. In the spring it is covered with tiny starry-white blossoms. It has a fibrous, shallow root system and is rather easy to pull or rake out.

Henbit grows erect to two feet, branches near the top, and purple (and sometimes white) flowers are borne in tight clusters in axils of leaves. It is about the only thing in bloom with tiny purple flowers (other than violets), so there can be little mistake in identifying it. It has an extensive but shallow root system and a small infestation can best be taken care of by pulling it out.

According to specialists, a weedkilling chemical containing silvex (sometimes sold as Chickweed Killer) is effective against both chickweed and henbit, and will not harm the grass if directions on the label are followed closely. Keep it away from broadleaf plants such as azaleas. Wait three months after seeding before spraying with silvex.

The dandelion is probably the most common of all lawn weeds other than crabgrass and needs no introduction. It has long, fleshy tap roots. When dug out, if only a tiny piece of the root is left, it will start new growth. On the credit side, the roots furnish a useful drug, the leaves are used as greens, and its flowers make an acceptable wine.

Plantain (the most distinctive thing is the upright seed stalk) has thick fleshy roots which develops numerous lateral rootlets making it one of the most difficult plants to eradicate by pulling or digging. It is a prolific seeder.

Spraying with 2,4D can be effective against both dandelion and plantain, without harm to the grass. Directions on the label should be followed closely. Don't spray with 2,4D when the least bit of wind is blowing.

Ground ivy is a low growing vine, propagated by seeds and rooting stems. The stems are 15 to 30 inches long forming roots at the nodes. Crushed stems or leaves have a minty odor. Small blue flowers are borne in clusters in the axils of leaves. Silvex and dicamba are the most effective weed-killers for ground ivy. Apply only when the weed is making active growth. Follow directions on label.

Crabgrass develops from seed produced in previous years, making its appearance only after hot weather has set in. Frost will kill crabgrass, leaving brown spots in the lawn. The best way to control crabgrass in lawns with only a few scattered plants is by persistent hand weeding before seed formation. Several weed-killing chemicals are available at large garden centers. Directors on the labels should be followed closely.