What are chickweed and henbit?
Chickweed and henbit are winter annual weeds that grow during cool weather. The seeds germinate primarily in the fall, and the plants continue to grow and live through the winter. They develop new seeds from April until early summer. Then they die.
Herron, J. W. and Thompson, Warren C., "Stamp Out Chickweed and Henbit from Alfalfa" (1966). Agronomy Notes. 209.