Rush skeletonweed is an exotic herbaceous biennial or creeping perennial plant indigenous to Central Asia and the Mediterranean region. Introduced into the eastern United States during the 1870s, it has since become troublesome in many western states. Rush skeletonweed is an aggressive plant that infests cropland, rangeland, and other disturbed areas. In particular, rush skeletonweed threatens the productivity of a) cropland (small grains, potatoes) due to an extensive root system that enables it to effectively compete with crops for water and nutrients (especially nitrogen), and because of its strong wiry stems and latex sap that interfere with harvest equipment; and b) rangeland through displacement of native or beneficial species, thereby reducing forage for livestock and wildlife.
Overall acreage infested with rush skeletonweed in the Pacific Northwest (defined here as Washington, Oregon, and Idaho) and California is in the millions and continues to increase, elevating rush skeletonweed to a top priority for many land managers. Rush skeletonweed is designated “noxious” and targeted for intensive control or eradication in the Pacific Northwest as well as California, Colorado, Montana, and Nevada. Arizona and South Dakota have taken action to prohibit the introduction of rush skeletonweed into their states. Curiously, rush skeletonweed is not currently listed by the federal government as a noxious weed.
Rush skeletonweed is a broadleaf plant in the sunflower (Asteraceae) family. It occurs as a rosette (Fig. 1A) from fall through early spring after germination and emergence and as a 1–4-foot-(0.3–1.2 m) tall plant during the summer. The rosette leaves are 2–5 inches (5–12 cm) long, ½–2 inches (1–5 cm) wide, hairless, and broader toward the tip than the base. The leaf margins have deep, irregular teeth with lobes that point backward toward the leaf base, similar to the rosette leaves of a dandelion
DISTINGUISHING RUSH SKELETONWEED ROSETTE TRAITS
- Teeth of leaves curve and point back toward the crown, resembling a dandelion
- Leaves are
- Leaves contain milky latex
KEY PLANT ID POINTS
- Wiry stems 1–4’ in
- Stem and aerial branches are nearly leafless and skeleton-like.
- Downward-pointing hairs cover the lower 4–6” of stem; the upper stem is smooth and
- Stems, leaves, and roots contain milky latex
- Roots have lateral shoots from which new plants develop.
Rush skeletonweed flower heads develop during the summer and bloom into late fall until the first killing frost. The bright yellow flowers (Fig. 1D) are small—less than an inch (2.5 cm) in diameter—and are scattered