Controlling Winter Lawn Weeds
During February, March, and April each year, my office receives numerous calls on lawn weeds. The best time to control them is between now and February. The first question we usually get is what should I spray to kill these weeds? This is a natural reaction, but it is not the only option for managing weeds. Proper lawn care and a healthy lawn are the best ways to prevent weeds. A lawn that is mowed at the proper height, aerated at the proper time, fertilized at the correct rates and times, and watered right will have fewer weeds.
Weeds in a lawn indicate poor growing conditions. Small hop clover, a common yellow flowering winter weed, indicates dry soil and low nitrogen. Annual bluegrass, a clump forming grass, grows actively during the winter and forms numerous seeds in the spring and indicates overly wet soils, compaction, and excess nitrogen. Moss indicates excess shade, poor drainage, and compacted soils. Other weeds commonly found in winter are dandelions, henbit (often identified by its attractive purple flowers), chickweed (a mat forming winter annual), wild garlic (most people call it wild onion), and Carolina geranium.
If an area is shaded, on a slope, or in a wet depression, grass cannot compete effectively against weeds that are better adapted to these conditions. If you have areas like this, you should consider landscape options other than grass. Ornamental ground covers can be used for shaded areas and slopes. Ornamental plants tolerant of wet sites can be used in wet areas.
When weeds occur in small numbers, pull or dig to remove the entire plant, including the roots. Where weeds occur in large numbers or are difficult to control, herbicides can be used to manage weed growth while cultural practices are improved to develop healthier grass.
Now is the time to control the weeds you normally see in late winter. Winter annual weeds start to germinate in September, grow slowly through January and February, and begin rapid growth and flowering in March. If you wait until March or April most weeds have grown so large that control is limited without costly and time consuming repeated applications. Weeds are smaller and easy to control now. Three and four way herbicides containing 2,4-D, mecoprop, dicamba, and possibly carfentrazone are recommended for bermudagrass, zoysiagrass and tall fescue lawns. Some herbicides containing these same ingredients are labeled for centipedegrass and St. Augustine lawns at lower rates, so use caution and always read the label before application. Southern Weed Killer for Lawns, Speed Zone Southern, Weed Stop, Weed Out, and Weed-B-Gone for Southern Lawns are a few of the over the counter products available with the ingredients listed above. St. Augustine, zoysiagrass, centipedegrass, and dormant bermudagrass can be treated with herbicides containing atrazine in November and December but if you missed that application due to wet or warm weather it is still OK to apply now. Atrazine controls annual bluegrass and many winter annual broadleaf weeds. Do not use atrazine on lawns over-seeded with annual or perennial ryegrass or other cool season grasses.
Wild garlic or wild onion is another weed that shows up in fall and winter. Control of wild garlic or wild onion can be obtained with Image herbicide, containing imazaquin now. With small infestations, spot treatment is suggested. Do not use Image with imazaquin on cool season grasses like tall fescue or warm season lawns over-seeded with annual or perennial ryegrass.
To ensure weed suppression, make sure to maintain lawns correctly. To obtain a lawn care calendar for the type of grass you are growing or ask a question call the Extension Master Gardener Volunteers at 902-1705. They have calendars for bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass. Leave your name, address, telephone number, and the type of grass you have. You can also find lawn calendars online at www.turffiles.ncsu.edu. Beware of generic recommendations that do not list specific grass types. Also be aware there are many specialty lawn herbicides available that may work better than the typical over the counter products I have listed here, particularly if you have hard to control perennial weeds. If you have lawn or gardening questions you can also email firstname.lastname@example.org.