Now is the time to control winter ANNUAL WEEDS
By Eric Barrett
OSU Ext. educator
Have you noticed lots of little seedlings that are staying small in the landscape? This late in the season, many of us are growing as tired as many of our plants. The lack of adequate rainfall the past few weeks has things looking rather down.
But we need to be paying attention to those little seedlings in flower beds, around sidewalks and around landscaped shrubs and trees. If you are looking closely, you’ll see the seedlings, ever meek and mild this time of year. They just emerged and will continue to gain strength through the late fall. When spring arrives, they will grow with explosive speed, bloom and create seed before you can blink. There is never time to get rid of them in the spring.
These weeds are called winter annuals. That is because they germinate now, stay green all winter and are done by early spring. Unlike summer annual weed species in the spring, winter annual weed species grow more actively at temperatures near freezing.
To control these weeds now, mulch is your best friend. Before mulching, use a hoe or string trimmer to remove the seedlings. Apply a fresh coat of mulch 2-3 inches thick on the area to block out the sunlight. This prevents other weed seeds from germinating.
In addition to weed control, the mulch will help moderate soil temperatures, aiding your plants through the freezes and thaws of early fall. This will allow roots to get a good foot hold before the colder temperatures of winter arrive.
In general, these weeds will be located where you had issues in early spring. If you know you had blooming weeds in an area in March, there may be a carpet of seedlings in that area right now. The three most abundant winter annuals we see in our clinic each year are:
Hairy bittercress. This plant will soon look like a small, rounded rosette of scalloped leaves. It emerges as two round cotyledons, then gains two scalloped, true leaves quickly. It is a lime-green color. It is a member of the mustard family. In spring, it will send up a central flower head with white flowers.
Purple deadnettle. The seedling looks similar to hairy bittercress at first, but is softer to the touch and has more of a spade shaped leaf. In spring, the upper leaves expand, turning a purple color with tiny pink/purple flowers.
Chickweed. These seedlings have more elongated, pointed leaves. It is a bright lime-green color.
Pictures of these annuals can be found at go.osu.edu/winterannuals.