The windblown pollen of Russian thistle can cause an allergic reaction in people during summer. As it uncoils, the taproot extends into the soil within about 12 hours, making the germination period quite rapid and giving Russian thistle a decided advantage under limited moisture conditions. A minimum amount of moisture, lasting only a few hours, will allow germination and root growth to deeper, subsurface moisture. Germination normally occurs in late winter or early spring when the seed can take advantage of winter moisture. Seed viability is rapidly lost in soil.
Russian thistle is extremely drought tolerant.
The taproot can extend several feet into the soil to reach subsurface moisture. Early leaves are linear and fleshy, much like pine needles, but as the plant matures, later leaves are short and spiney and much more capable of conserving moisture. Russian thistle normally matures in late summer. An abscission layer forms in the stem near the soil surface that allows the shoot to break off from the taproot in fall and early winter. A large Russian thistle plant may produce more than 200,000 seed.