Cool season turf weeds are getting well established as we move into late October. This weed group includes annuals and perennials such as wild garlic, henbit, chickweed, hop clover, annual bluegrass and many others. These weeds are particularly troublesome because they come to maturity when our warm season lawns are just getting started for the new growing season. So we end up with what tends to be the most unsightly and aggressive weed infestations of the year, at precisely the time when our lawns are most vulnerable to herbicide damage.

 

The best strategy for avoiding this scenario is to get serious with weed control prior to Christmas, rather than waiting until March or April. Our wild garlic and wild onion populations provide a good place to start the conversation.

 

These perennial cool season weeds began to emerge in September, and are now actively growing and easy to spot. On centipedegrass, spot sprays with a labelled turf herbicide containing 2,4-D; or a product containing imazaquin (Image, others), can be quite effective during mild weather when the wild garlic and wild onion plants are small and growing rapidly. Spraying now also leaves time for a follow up spray prior to spring, which will likely be needed when using 2,4-D.

 

Metsulfuron should also be mentioned. While considered a professional applicator product in the past, various metsulfuron products are now showing up on the homeowner market – although primarily on line. Metsulfuron should be handled carefully, and often leads to temporary yellowing of the turf. But especially if a lawn care professional is making the applications for you, metsulfuron is a very effective tool to consider for wild garlic and wild onion.

 

Most of the broadleaf winter turf weeds can be controlled using the same products. One point of clarification is that you will most likely access 2,4-D in one of the “three-way” home lawn products containing 2,4-D + MCPP + Dicamba. These products often contain an additional material such as carfentrazone or sulfentrazone, which enhances efficacy of the product against a broad range of weed species. An agricultural 2,4-D product with no mention of centipedegrass on the label will likely be too strong for safe use on centipedegrass (or St. Augustinegrass), and the label won’t be of any help in providing rate and application instructions.

 

Annual bluegrass (Poa annua) is in a unique category as a winter annual grassy weed. Especially given the limited range of homeowner products available for control of this weed, timing is critical. Products containing atrazine can be applied in mid November to control annual bluegrass that has already emerged, and to also provide pre emergent control of later germination. Certainty is a fairly new product to consider for annual bluegrass. It’s relatively expensive compared to other home lawn herbicide products, but in addition to annual bluegrass control, it’s also highly effective against the summer annual Virginia buttonweed.

 

Carefully evaluate site conditions this winter, and remember that herbicides cannot be relied upon to keep a lawn “weed free” (“weed free” being an unreasonable goal in the first place). Many lawn areas are too compacted, too shady, too wet, too sandy, or too something to support a healthy cover of turf. In these cases, improving site conditions or switching to something other than turf will be the more sustainable, environmentally friendly option.