Whitlow grass (Draba verna)
Travis Legleiter, Weed Science Program Specialist, Department of Botany & Plant Pathology
Many questions are being asked of entomologists, plant pathologists, agronomists, and weed scientists about the effects of the mild winter and early spring on the upcoming growing season. While you will likely not get a straight answer out of any of these experts, a simple stroll through your yard or a drive past a couple of agronomic fields will answer one question. That is, that winter annual weeds have taken full advantage of the mild winter, early spring, and uncharacteristically warm weather of the last couple of weeks. Many corn and soybean fields have turned a mixture of green and purple with chickweed, henbit, and purple deadnettle amongst other winter annual weeds. The weather conditions have not only allowed predominate winter annual weeds to flourish, but have also allowed some typically inconspicuous weeds such as Whitlow grass to become a little more noticeable.
Whitlow grass, a member of the brassica or mustard family, is actually not a grass as the name indicates. Whitlow grass is also referred to as shad flower, nailwort, and vernal whitlow-grass. This winter annual can also exist as a biannual and is often overlooked as it flowers, sets seed, and matures prior to typical corn and soybean burndown programs in April and May.
Whitlow grass grows as a very small basal rosette with spatulate to oblong leaves that are 0.5 to 1 inch long and covered with stiff white hairs. Multiple leafless reproductive stems will emerge from the rosette and typically elongate 1 to 5” above the rosette. The reproductive stems will have multiple flowers with 4 deeply divided white petals that can be mistaken for 8 petals if not closely inspected. Small brown seedpods produced by whitlow grass are oblong and often clasped by the flower petals or sepals.
This inconspicuous winter annual weed is often overlooked because of its small size and early spring maturation, but may be more noticeable in fields this spring with the unusual weather. Whitlow grass is not considered to be problem weed or hard to control weed. Herbicide burndown programs and spring cultural practices used to control other winter annual weeds will also adequately control whitlow grass.
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Photos courtesy of John Orick, ANR Educator, Madison County