Q. These plants are growing in my lawn. Can you tell me what they are and how to control them? And what about controlling crabgrass?
A. See image with arrows and names of your samples. Without knowing what type of turf you have, I’m assuming your priority is maintaining a centipedegrass lawn rather than bermudagrass. That being the case, bermuda can be very hard to suppress, but your best option on the garden center market will be a product containing sethoxydim. This is a post-emergent, over the top material that can selectively kill or suppress grassy weeds in centipedegrass during the growing season. Brand names might include Poast, Vantage or Hi-Yield Grassy Weed Killer. The safest herbicide for controlling annual bluegrass in centipedegrass is probably atrazine. Unfortunately, the time to apply atrazine for annual bluegrass would have been mid-November and mid-December. There isn’t much hope of selective control this time of year. Regarding crabgrass, pre-emergent products in the dinitroaniline (DNA) group (such as benefin, oryzalin, prodiamine, pendimethalin, and trifluralin; also, the non-DNA dithiopyr) can damage centipedegrass root tips, and aren’t the first choice. Atrazine, however, is very safe on centipedegrass and can be used about anytime. A preemergent application for crabgrass could be made in mid- March. Once the lawn has fully greened up, ideally no sooner than mid to late May, you could use sethoxydim to selectively suppress crabgrass. Also, carefully assess the site to make sure infested areas aren’t more suitable for weeds than for turf.
From an NCSU information note: Management practices that encourage annual bluegrass persistence include: 1) excessively close mowing; 2) shallow, frequent irrigation; 3) poor soil drainage; 4) improperly timed fertilization; 5) aerifying or dethatching during primary periods of germination; 6) use of heavy equipment causing compaction; and 7) shade.
Many other winter annual and biennial weeds are growing in landscapes as well, and intervention is needed to clean things up and reduce seed production for next year. Carolina geranium (Geranium carolinianum) is one of the most prominent, but there are many others including hairy bittercress, annual bluegrass, chickweed and common vetch. In landscape beds, management can include spot sprays of postemergent non-selective herbicides (for example, glyphosate or one of the organic products), but hand-pulling is also effective in landscape beds if the square footage is not overwhelming. Pulling the weeds now, prior to seed production, is a critical part of long-range management. Look at it as a routine chore during January through March. Just a few minutes of hand-pulling a day can make a huge difference.
The mission of the Craven County Extension Master Gardener Volunteers is to provide research-based information about gardening, environmental stewardship and best horticulture practices to the community. If you have gardening questions, you can email [email protected], call 633-1477, stop by at our Saturday Farmers Market booth or attend one of our many lectures, tours or workshops.
