Foxtail grasses are common annual plants found across North America, often appearing innocuous in fields, along roadsides, and in residential areas. These plants are frequently categorized as invasive weeds that spread easily in disturbed soil. While the vegetative part of the plant is harmless, the structure designed for seed dispersal poses a significant and often unexpected threat to domestic animals and, in some cases, livestock. Understanding the unique physical structure of the foxtail seed head is the first step in recognizing the danger it presents.
Detailed Physical Characteristics
The danger of foxtails lies within the dry seed head, which is technically a cluster of spikelets that resembles a bottlebrush or the tail of a fox. Early in the growing season, these seed heads are soft, green, and relatively harmless, but as summer progresses, they mature and dry out, turning stiff, brittle, and a pale golden-brown color. This maturation process causes the seed cluster to break apart easily, releasing individual spikelets, also known as awns, which are the problematic components.
Each individual awn is slender, rigid, and tipped with a sharp, pointed end. The most concerning feature is the presence of microscopic, backward-facing barbs that cover the awn’s surface. These retrorse barbs are angled away from the tip, creating a highly specialized structure that functions like a one-way ratchet. The awn’s geometry allows it to easily slide forward when pressure is applied, but prevents it from backing out of a material. This barb structure is an evolutionary adaptation for seed dispersal, helping the awn cling to fur or clothing. The hardened tip allows the awn to penetrate soft tissue with minimal resistance, meaning that once lodged into a host, any subsequent movement will only drive the seed deeper into the body.
Where Foxtails Thrive and Spread
Foxtail grasses are not a single species but a collection of plants, including varieties of Setaria and Hordeum, that share this common, dangerous seed structure. While they are native to North America, they have become widespread weeds, particularly prevalent in the western United States. Their distribution extends across most of the country, especially in areas with hot, dry summers.
These grasses flourish in environments characterized by disturbed soil and minimal competition from other plants. Common habitats include open fields, vacant lots, agricultural margins, roadsides, and unmaintained lawns. Foxtails are annual grasses, sprouting in the spring and producing their seed heads from late spring through the summer months. A single plant can produce hundreds of barbed awns, which are readily dispersed by wind, water, animals, and human activity. The seeds remain viable in the soil for months, ensuring a new crop of plants the following year.
The Danger: How Foxtails Cause Harm
The primary danger arises from the awn’s ability to penetrate and migrate through soft tissue, acting as a foreign body that can carry bacteria deep inside the host. The backward-facing barbs prevent the body’s natural muscular and skin movements from expelling the awn. Instead, movement, such as walking or shaking the head, only serves to propel the barbed seed further along its path.
Common entry points for these migrating awns include the sensitive, thin skin between a dog’s toes, the ear canal, nasal passages, and the eyes.
Symptoms of Foxtail Penetration
When a foxtail enters a paw, it often causes limping or excessive licking, and if left untreated, it can track deep into the limb, leading to abscesses and severe localized infection. Awns entering the ears often cause sudden, violent head shaking and pawing at the ear, sometimes resulting in a ruptured eardrum as the seed migrates toward the inner ear.
Inhalation is a particularly severe risk, where a foxtail can be drawn deep into the nasal cavity, triggering intense, persistent sneezing or a bloody discharge. From the nose, the awn can potentially travel into the pharynx, and in rare but serious cases, migrate into the chest cavity, leading to a life-threatening condition called pyothorax, or pus accumulation in the lungs. Once inside the body, the awns can continue to travel, causing chronic inflammation, infection, and abscesses in almost any organ or tissue they encounter.
Strategies for Management and Removal
Managing foxtail grass in the environment requires consistent effort, focusing on preventing the plants from reaching the dangerous, dry seed-head stage.
Environmental Control
In smaller areas, like residential yards, the most effective physical control method is hand-pulling the grass before the seed heads begin to mature and turn brown. If the plants have already formed seed heads, they should be carefully removed and bagged rather than composted, as the seeds can survive and spread. For larger areas, applying a pre-emergent herbicide in early spring, before the seeds germinate, can significantly reduce the population for the season. Regular mowing can help, but it must be done before the seed heads fully develop, as mowing mature, dry foxtails will simply scatter the barbed awns across the property.
Pet Prevention
Preventative measures for pets are paramount during foxtail season, especially in the summer. Thoroughly inspecting a pet’s fur immediately after outdoor activity is highly recommended. Inspection should focus on areas like between the toes, around the ears, under the armpits, and in the groin area. Long-haired breeds may benefit from shorter summer haircuts to reduce the surface area where the awns can attach and hide. If a pet exhibits any sudden, persistent symptoms like extreme head shaking, violent sneezing, or constant licking of a paw, immediate veterinary examination is necessary to locate and remove any embedded awns.