RUSSIAN THISTLE, Solsola
koli L. var. tenuifolia Tausch. 1, branch; 2, root;
3, portion of older branch; 4, seed in hull; 5, seed,
hull removed. Annual, reproducing by seed. Stem profusely
branched, 1 to 3 feet (30 to 90 cm) high, forming typical ball-like tumbleweed
at maturity. Young plants soft, succulent; mature plants stiff and woody.
Leaves cylindrical or awl-shaped. Young leaves long, soft. Later
leaves short, stiff, prickle pointed. Flowers numerous, small, without
petals, axillary on upper branches. At maturity, entire plant may be splashed
with red color; stem breaks from root and moves freely across open fields
with winds scattering the seed. Found in spring grain and legume
seedings. An important annual weed, it is most troublesome in dry years.