Extension Educator, Horticulture
Just when you think your weeding worries are over for the year, a few weeds sneak in to your garden. We typically think of seeds germinating in the spring. However some weed seeds actually germinate in the fall. These weeds are called winter annuals. The young plants are very cold hardy and often stay green late in the season. The same plants then flower in early spring and form many seeds. These weeds are probably lurking in your garden right now. Winter annuals will appear in areas where the soil has been disturbed such as through tilling, where the dog dug, where the kids make shortcuts, etc. in lawns, gardens, fields and strawberry and asparagus beds.
Henbit, Lamium amplexicaule, is often confused with creeping Charlie, Glechoma hederacea. Both have square stems and are in the mint family. Both have lavender to blue tubular flowers. In my opinion henbit flowers tend to be more on the purple/lavender range and are clustered at stem tips with clasping leaves below the flower cluster. Creeping Charlie flowers tend to be more in the blue range without the clasping leaves. Both plants have round shaped, scalloped leaves. A couple differences between henbit and creeping Charlie include the life cycle and flowering time and therefore control measures. Henbit is a winter annual and creeping Charlie is a perennial. The original creeping Charlie plants come back every year. Henbit has to start from seed each year. Henbit as a winter annual blooms very early in the spring and well before creeping Charlie blooms. Around here you will often see whole farm fields of henbit in bloom early in the season. Forgetting the weedy aspects of the plant, it really is quite pretty.
Common chickweed, Stellaria media, is a low spreading plant that can grow 4-12 inches tall. It often grows in the shade of trees and shrubs or the north side of buildings. Chickweed has light green, small and ovate shaped leaves with pointed tips. The flowers are small, white with five deeply notched petals. The stems are creeping and often root at the leaf nodes.
Another group of winter annuals are the speedwells, Veronica spp.. Corn speedwell, Veronica arvensis, is common here. It is appearing and even flowering right now. Seeds may also germinate in early spring. The leaves are small with scalloped edges. The flowers are blue with a white center.
Shepherdspurse, Capsella bursa-pastoris, seemed to be quite prevalent this last spring, which translates into many seeds waiting to germinate this fall. In the fall shepherdspurse will appear as deeply lobed leaves in flat rosettes. It blooms in very early spring. The small white flowers appear on 6-8inch stalks. The flowers develop into triangular shaped seedpods. Someone decided the pods looked like a purse once carried by shepherds. Shepherdspurse is widely found in disturbed soil areas and the seed is long-lived in the soil.
Control of winter annuals includes removing plants now by hoeing or hand pulling. Broadleaf herbicides can also be effective if used while the weed is actively growing now or before the weed flowers in early spring. Realize herbicides are not effective at cold temperatures. Be sure to read and follow all label directions.
Once annuals flower and form seeds, controlling the original plants does nothing for future control. It only makes you feel better due to the revenge factor. Control of perennial weeds such as creeping Charlie is in controlling the original plant through hoeing, hand removal or herbicides and in controlling seed production.
With any weed control, accurate identification is important. Check your local library for weed identification books or bring samples to your local U of I Extension office. Control measures applied at the wrong time may be ineffectual so don't put away your hoe just yet.