At this time of year, crabgrass is usually gone from the lawn. The first frost kills it. In its place appear two winter annual weeds, chickweed and henbit, along with two perennial weeds, dandelion and wild garlic.
Seeds of chickweek and henbit germinate during October and November. The plants grow in late fall and winter, bloom from April until early summer, then die. They produce millions of seeds. The tiny white flowers of chickweed and reddish-purple ones of henbit stand out in early spring when few other things are in bloom.
Dandelion is a pernicious weed with a long, fleshy taproot. The flowers make an acceptable wine, the leaves are good eating as greens and the roots furnish a useful drug.
But there's nothing good to be said for wild garlic. The bulbous base produces myriad secondary bulbs or bulblets, each of which can produce new shoots the following year. Pulling the plants by hand multiplies them instead of decreasing them.
Fall is probably the best time to try to rid your lawn of these weeds. They're just getting started and are easiest to control when small. Also, there's less chance of damaging shrubs as they're making little if any above-ground growth this time of year.
A measure of control of chickweed, henbit and wild garlic can be achieved with just the lawnmower. But for more control, specialists recommend spraying with dicamba. Spray on a day when there is no wind blowing and the temperature is above 60 degrees. Directions on the label should be followed closely.
If the first application doesn't get rid of them, repeat the treatment two weeks later.
Only the tops of wild garlic will be killed: This keeps the top from producing food for the bulblets. If this is accomplished for about three years, the bulblets will die of starvation.
Dicamba will control weeds without harming the grass, but may be hazardous in areas where tree roots are growing. When using weed-killing chemicals, instead of treating the entire lawn, spray only the places where the young weeds are.
Fertilizers containing dicamba or other weed-killing chemicals should be applied with caution. Roots of established trees and shrubs often extend far beyond the drip-line of their branches; when applied on slopes, the chemicals can wash downhill in the first heavy rain and damage these roots.