In many cases, controlling winter weeds in the dead of winter is not a great idea. Once cold weather sets in, winter weed growth slows down significantly. Even nonselective herbicides struggle to kill weeds such as henbit, annual bluegrass and perennials such as white clover when applied in winter months. Winter weeds will basically go dormant but stay green and survive through snow and ice. When spring and warmer temperatures approach, winter weed growth and development resumes quickly. Spring would be a better time to successfully control winter weeds once they resume growing. Turfgrass that have winter weeds in winter months had winter weeds in fall months as well. Whether from procrastination or just the fact that the weeds were so small they were not noticeable in the fall, winter weed control applications are possible in some instances.
Warm-season turfgrasses, especially bermudagrass, allow for winter applications of certain herbicides because of dormancy. There are several herbicides (selective and nonselective) that are effective on annual bluegrass, various winter annual broadleaf weeds and wild garlic, but could be injurious to transitioning or fully green warm-season turfgrass. Therefore, the ideal timing for these herbicide applications would be winter months when the turfgrass is dormant. Check actual herbicide labels for the most accurate information concerning turfgrass tolerances, rates, adjuvant requirements, timings and weed species controlled.
Dormant bermudagrass only: annual bluegrass and various annual broadleaf weeds
Roundup, Finale and QuikPro are nonselective herbicides that must only be applied to dormant bermudagrass. Do not apply these herbicides to dormant zoysiagrass, centipedegrass or St. Augustinegrass! Injury (delayed greenup and possibly death) will be observed during spring transition. When temperatures are 60 F or greater, apply Roundup at 0.5 lb ai/A, Finale at 3 to 6 qt/A or QuikPro at 5 to 9 oz/A depending on weed species and size. At these rates, very few perennial weeds (dandelion, white clover) will be controlled. Sencor 75 Turf must also be applied to dormant bermudagrass before spring transition or greenup will be delayed. Sencor 75 Turf applied at 0.67 lb/A controls annual bluegrass and various winter annual broadleaf weeds.
SureGuard is a new herbicide from Valent USA Corporation. SureGuard applied to dormant bermudagrass at 8 to 12 oz/A will control annual bluegrass and winter annual broadleaf weeds such as henbit, chickweed, geranium and hairy bittercress. Another benefit of SureGuard is preemergence crabgrass control. With proper application timing, SureGuard provides postemergence winter annual weed control and preemergence summer annual grass control through mid-summer with a single application. Do not apply SureGuard to actively growing or transitioning bermudagrass as unacceptable injury and/or greenup delay will occur!
Wild garlic control
Image 70DG is recommended for wild garlic control in winter months only, because warm-season turfgrasses are affected when transitioning to active green growth. Image 70DG can be applied up to 0.7 lb/A to dormant bermudagrass, centipedegrass, zoysiagrass and St. Augustinegrass.