Winter Lawn Weed Management
During February, March, and April each year, my office receives numerous calls on weeds in lawns. The best time to control these weeds 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. Soil testing is the best place to start. The North Carolina Department of Agriculture and Consumer Services will start charging $4 per soil sample as of November 27, 2013 through March 31, 2014. If you want to bring a soil sample by the Pitt County Extension office so it will get to Raleigh prior to the charge, I suggest having it to us by November 22. After that date contact the Master Gardeners to determine the best way to get samples to the lab. The results will tell you if lime and fertilizer are needed.
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 for the grass. 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 get started if you see weeds showing up in large numbers or have had weed problems in the past. Winter annual weeds start to germinate in September, grow slowly through January, and begin rapid growth and flowering in February and March. If you wait until February, March, or April, most weeds have grown so large that control is limited without costly and time consuming repeated applications. If you start now weeds are small and easy to control. Three way herbicides containing 2,4-D, mecoprop, and dicamba 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, Weed Stop, Weed Out, and Weed-B-Gone 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. 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 the fall. Control of wild garlic or wild onion can be obtained with Image herbicide, containing imazaquin now through December. 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. Starting November 18, Master Gardeners will shorten their office days from Monday through Friday to Mondays and Thursdays from 10 a.m. to 12 p.m. for walk in visitors and to take and return calls.