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The Homeowners Column
Winter Annuals Enjoy Cold Weather
Extension Educator, Horticulture
As you wander your landscape you may be surprised to see the fresh green leaves of a few seemingly confused plants. We think seeds typically germinate only in the spring. However some seeds purposefully germinate in the fall, especially when we have warmer-than-usual weather.
Plants whose seeds germinate in fall or late winter and then flower and set seed in early spring are called winter annuals. The young plants are very cold hardy and often stay green late into fall and are often the first plants to grow in early spring. The same plants that raise their heads in fall are the same plants that flower in early spring. The original plant dies but leaves a multitude of seeds in our garden beds long before we dig out our garden boots. Winter annual seeds germinate in non-mulched, bare soil areas in flower beds and vegetable gardens and along driveways and paths.
A common winter annual, Henbit (Lamium amplexicaule) is often confused with Creeping Charlie (Ground ivy), Glechoma hederacea. Both have square stems and are in the mint family with small tubular flowers. Henbit flowers are more in the purple/lavender color range and are clustered at stem tips with clasping leaves below the flower cluster. Creeping Charlie flowers are blue without the clasping leaves. Both plants have round shaped, scalloped leaves and are often considered weeds.
A couple differences between Henbit and Creeping Charlie include the life span and flowering time. 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 purple flowered Henbit early in the season.
Common Chickweed, Stellaria media, is a low spreading winter annual 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, commonly grows here and may be flowering right now. The leaves are small with scalloped edges. The flowers are blue with a white center.
Shepherdspurse, Capsella bursa-pastoris, plants may be abundant now as deeply lobed leaves in flat rosettes. In early spring the small white flowers appear on 6-8 inch stalks. The flowers develop into triangular shaped seedpods.
For wild food foragers winter annuals are a tasty treat as fresh greens when most other plants are brown. Chickweed salad comes to mind. Whether your goal is slathering with butter or slaughtering with a hoe, accurate plant identification is crucial. Check your library for weed identification books or bring samples to your local U of I Extension office.
If you choose to control winter annual weeds, hoeing or hand pulling now is a good option. Smothering with wood chips also works. Broadleaf herbicides can be effective if used while weed is actively growing or before it flowers in early spring. Remember herbicides are not effective at cold temperatures. Be sure to read and follow all label directions.
Once annual plants flower and form seeds, destroying the original plants help little in stopping future plant development. Beat 'em or eat 'em winter annuals are green and growing when other plants are dead and decomposing.