Henbit (Lamium amplexicaule) is a cool season, ANNUAL broadleaf weed with square stems and pink to purple flowers. It is mostly noticed in the early spring after it has had a chance to grow all winter in the lawn and then begins to bloom. These blooms produce seed which will lay dormant over the hot summer, then begin to germinate in the fall as the temperatures cool. The plant itself dies completely in hot temperatures and does not come back from the roots.
Wild Carrot (Daucus carota) is a biennial broadleaf weed which behaves as an ANNUAL in our climate. Introduced from Europe, and an ancestor of the cultivated carrot, it has now spread throughout the United States. The seeds germinate in the fall when temperatures are cool. The plant forms a “winter rosette” close to the ground, eventually sending up erect single stems 1-3 feet tall. The plant blooms in spring though early summer, producing a white, flat-topped bloom which bears many thousands of seeds. The seeds have hooked spines that cling to animal fur and clothing, spreading the plant far and wide. Seeds can remain dormant in the soil for 2-5 years. When pulled, the taproot smells like carrot. The entire plant dies after blooming and setting seed. It does not come back from the roots.
Carolina Geranium (Geranium carolinianum) is a broadleaf ANNUAL weed that germinates from seed as the temperatures cool in the fall. The plant grows in the winter months from a single taproot, sometimes reaching 24” across. Small white blooms appear in early spring producing seeds that will lay dormant until temperatures cool in the fall. The entire plant dies in high temperatures and does not grow back from the roots.
Annual Bluegrass This clumping ANNUAL grass germinates from seed as the temperatures cool in the fall. We notice it more in the spring because it has produced light colored seed which is more visible. You will likely notice that the seed is produced close to the ground, so mowing will not lessen the number of seed produced for the next season. It will die off completely when it gets hot.
Rescuegrass is a cool season ANNUAL grass that has flattened seed spikelets and hairy leaf sheaths and upper sides of the leaf blades. It has become a common weed in lawns. It will die off completely in the summer months.
Common Chickweed is yet another cool season ANNUAL weed that we may not notice until spring when it blooms. It will die off completely when it gets hot.
All of these weeds have something in common. You may have noticed that I highlighted ANNUAL in red. Annual weeds live until they produce seed or when the temperatures that they prefer change. We often do not notice them until the spring, but that is NOT when they should be controlled! They are easily controlled by the application of an appropriate pre-emergent in the FALL before the seeds have begun to germinate. Young seedlings may be controlled by an appropriate selective post-emergent herbicide after the lawn is dormant in the fall. It is much easier to prevent this weed than to control it after it has germinated.