Foxtail weed is the common name for several species of grasses in the genus Setaria and related genera, widely recognized for their distinctive, bristly seed heads. This widespread grass is a common sight across North America, often found in disturbed soils, lawns, fields, and along roadsides. While the plant is not chemically poisonous, it poses a significant physical danger to both domestic animals and livestock. The sharp, arrow-like seeds detach once mature and can embed themselves in soft tissue, migrating dangerously inside the body.
Identifying the Plant and Its Growth Habits
Foxtail grasses are typically summer annuals, though some species can behave as perennials, growing in clumps with a fibrous root system. In their early, vegetative stage, they resemble common turf or crabgrass. The danger begins when the plant transitions into its reproductive stage, usually from mid-summer to fall, developing the characteristic seed head.
The seed heads, which give the plant its name, are dense, cylindrical spikes composed of numerous individual seeds with fine bristles. Common varieties include yellow foxtail (Setaria pumila), green foxtail (Setaria viridis), and giant foxtail (Setaria faberi). These bristly heads can range from a few inches to over half a foot in length, often having a fuzzy, brush-like appearance. The mature seed head easily breaks off when dry and is designed to cling to fur and clothing.
Understanding the Mechanism of Harm
The threat posed by the foxtail seed head lies in the unique, one-way design of its awns. These needle-sharp bristles are covered in backward-pointing barbs that act like a ratchet, allowing the seed to move only in a forward direction. Once embedded in soft tissue, normal muscle movement causes the seed to burrow deeper, preventing it from backing out naturally.
Foxtails are most commonly found lodged in a pet’s paws, ears, eyes, nose, and throat. A pet constantly licking their paw, developing a swollen lump between the toes, or limping may indicate a foxtail embedded in the skin of their foot. If a seed enters the ear canal, symptoms include violent head shaking, persistent scratching, or a noticeable head tilt.
The seeds can also be inhaled, leading to lodging in the nasal passage, which results in explosive sneezing or bloody nasal discharge. If swallowed or inhaled deeply, the awn can migrate into the lungs or other internal organs, causing severe abscesses or a life-threatening condition like pyothorax. Because the body cannot break down the plant material and the barbs prevent reverse migration, veterinary attention is mandatory for any suspected internal lodging.
Eradication and Control Methods
Effective foxtail management requires an integrated approach combining mechanical, cultural, and chemical controls. The most important preventative measure is to remove the plant before its seeds mature and drop. Once seeds are present, mowing is ineffective and can spread the seeds, allowing the plant to continue dispersing.
Mechanical removal involves hand-pulling individual plants, ensuring the entire fibrous root system is removed. If a larger area is infested, tilling the soil can turn the plants under, helping them degrade. For lawns, a strong cultural control program is the best defense, as a dense, healthy turf crowds out the foxtail. This includes proper fertilization and irrigation to encourage vigorous growth.
Chemical control is divided into pre-emergent and post-emergent strategies. Pre-emergent herbicides are applied in early spring before the foxtail seeds germinate, creating a chemical barrier in the soil. For existing plants, selective post-emergent herbicides targeting grassy weeds must be used, as broadleaf weed killers are ineffective. Post-emergent treatments are most effective when the foxtail plants are young, often requiring follow-up applications.