Foxtail is a common summer annual grassy weed that challenges lawn owners because it is botanically similar to desirable turfgrasses. Controlling it requires a selective treatment that targets the weed without harming the surrounding lawn, as most non-selective herbicides will kill both. Selective control relies on exploiting the subtle differences in biochemistry and life cycle between the weed and the turf.
Identifying Foxtail Species and Growth Patterns
Effective management of foxtail begins with accurate identification of the species present. The three most common types found in turfgrass are Green, Yellow, and Giant foxtail, all of which share a summer annual life cycle. Foxtail seeds begin to sprout when soil temperatures consistently reach 65°F, with optimum germination occurring between 70°F and 85°F.
Distinguishing the species involves examining the leaves and seed heads. Yellow foxtail has sparse, long, silky hairs located at the base of the leaf blade, while Giant foxtail features dense, short, fine hairs across the entire upper leaf surface. Green foxtail is typically hairless on the leaf blade, and its seed head is smaller and more slender than the others.
Preventing Foxtail with Pre-Emergent Herbicides
The most effective method for controlling foxtail without harming established grass is prevention through the use of pre-emergent herbicides. These products work by creating a chemical barrier near the soil surface that kills the foxtail seedling shortly after the seed germinates.
The timing of application is paramount for success, requiring treatment before soil temperatures reach the 65°F threshold for foxtail germination. Applying the product too late means the foxtail seeds have already begun to sprout, rendering the barrier ineffective. Common active ingredients used include prodiamine, pendimethalin, and dithiopyr, which are safe for most established turf varieties.
Selective Post-Emergent Chemical Control
When foxtail plants have already emerged and are actively growing, a post-emergent herbicide is necessary to achieve selective control. This approach uses chemicals absorbed by the foxtail plant to disrupt its growth processes, while the desirable turfgrass remains largely unaffected. The specific product choice depends heavily on the type of turfgrass in the lawn, as selectivity is not universal.
Cool-Season Grasses
For cool-season grasses such as Kentucky bluegrass, fescue, and perennial ryegrass, active ingredients like quinclorac or fenoxaprop-p-ethyl offer good control. Quinclorac is effective against young foxtail plants by disrupting cell wall synthesis, but it can harm certain warm-season species like St. Augustinegrass. Fenoxaprop-p-ethyl, often marketed as Acclaim Extra, inhibits fatty acid synthesis in the foxtail without damaging the cool-season lawn.
Warm-Season Grasses
Managing foxtail in warm-season turfgrasses, including Bermudagrass and Zoysiagrass, often involves different active ingredients. Metsulfuron methyl provides control of various weeds, including foxtail, and is safe for use on many warm-season lawns. Another option is topramezone, which inhibits a specific enzyme in the foxtail, causing it to turn white and eventually die.
Cultural Practices for Long-Term Foxtail Management
Beyond chemical intervention, adopting sound cultural practices is an effective long-term strategy for minimizing foxtail infestations. The goal is to create a dense, vigorous turf canopy that outcompetes the annual weed for sunlight, water, and nutrients. A thick stand of turf naturally shades the soil, which keeps the ground temperature lower and inhibits seed germination.
Raising the mowing height to between three and four inches allows the desirable grass to develop a deeper root system and provides more shading. Proper watering techniques are also important; deep, infrequent watering encourages strong, deep-rooted turfgrass growth, whereas frequent, shallow watering favors the annual foxtail. Care should also be taken with fertilization, particularly reducing nitrogen applications during the foxtail’s peak germination period to avoid fueling the weed’s growth.