Foxtails are annual summer grasses. Three species are common in the United States: yellow foxtail (Setaria pumila or Setaria glauca), green foxtail (Setaria viridis) and giant foxtail (Setaria faberi). These grasses have many structural similarities and share a characteristic brush-like seed head that resembles the tail of a fox. Foxtails often are serious weed problems in lawns, gardens, cropland and orchards. They multiply rapidly because they produce a lot of seeds. To identify and differentiate foxtail grasses from other grasses, note where they grow and examine their stems, blades and seed heads.
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Habitat and Distribution
Foxtail grasses usually grow in clumps, and green and yellow foxtails grow 1 to 3 feet tall, while giant foxtail ranges between 3 and 7 feet in height. The habitat for foxtails is in disturbed areas, such as croplands, gravelly areas along roads, and cracks in sidewalks and parking lots that expose bare soil. Foxtails prefer fertile soil, but will sometimes grow in poor soil. The grasses are less likely to grow in natural undisturbed areas. You can find yellow and green foxtails all across the United States, while giant foxtail predominates in the southeast.
Examination of the collar region helps you identify and distinguish different types of grasses. The stems of grasses are enclosed by a sheath and the collar region is the juncture where the sheath meets the grass blade. The juncture contains a thin membranous projection, called a ligule, that characterizes and can differentiate grasses. Pull the grass blade slightly back to get a good look at the ligule. The ligule of foxtail grasses contains a distinguishing fringe of short dense hairs.
Foxtail blades are flat and range from a width of 1/4 to 1/2 inch in green and yellow foxtails. The blades of giant foxtail are 1/2 inch wide or wider. Both yellow and giant foxtails have hairs on the upper surfaces of their blades, while green foxtail has a smooth blade surface.
The seeds in foxtails develop from small flower heads that are attached to bristles. Yellow foxtails have seedheads up to 3 inches long and have short, coarse bristles. Green foxtails have soft, nodding seedheads up to 6 inches long, while giant foxtails have 3- to 7-inch seedheads that tend to droop. Bristles on green and giant foxtails are longer than on yellow foxtails. The flowers of foxtails are pollinated by wind, and when the seeds develop, they drop to the ground and are spread to other areas by wildlife after the animals ingest the seeds.