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. All county centers of North Carolina Cooperative Extension have soil testing boxes and sheets that can be filled out to send your sample to the North Carolina Department of Agriculture and Consumer Services for testing. 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 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 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. 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 902-1705. Leave your name, address, telephone number, and the type of grass you have. We have calendars for bermudagrass, centipedegrass, Kentucky bluegrass, St. Augustine, tall fescue, and zoysiagrass. Lawn care calendars are a great guide to proper maintenance for your lawn type during specific seasons. You can also find them online at www.turffiles.ncsu.edu. Beware of generic recommendations that do not list specific grass types. Also, 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 weeds. If you have lawn or gardening questions you can also email pittcomgv@hotmail.com. From now through February, Master Gardeners will be in the office on Mondays and Thursdays from 10 am to 12 pm to take and return calls. If you are interested in becoming a Master Gardener the application deadline is November 16 so call 902-1709 now.

Written By

Danny LauderdaleExtension Agent, Agriculture (252) 902-1701 Pitt County, North Carolina

Posted on Nov 26, 2012

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