Russian thistle, Salsola pestifer A. Nels., [SASKR, soude roulante, Saltwort, Tumble-weed, chardon de Russie, herbe roulante de Russie, Salsosa iberica Sennen & Pau. S. Kali L. var. tenuifolia Tausch, S. tragus L. subsp. iberica Sennen & Pau ] Annual, reproducing only by seed. A very bushy, much-branched, spiny plant 5 - 120 cm (2 in. - 4 ft) high, its diameter often exceeding its height; stems green, usually striped with red lines, and rough with short, firm hair; cotyledons (seed leaves) very narrow and grass-like, gradually lengthening and reaching 3 - 5 cm (1 - 2 in.) long; first true leaves apparently opposite (2 per node), as long as or longer than the cotyledons, needle-like. round or slightly flattened in cross-section, softly sharp-pointed; later leaves gradually shorter but mostly alternate (1 per node); young plants often with crowded erect leaves and resembling a grass; older plants with firm, short, bract-like leaves, usually only 6 mm (¼ in.) long, with a broad base tapering to a slender point and ending in a hard, sharp spine; flowers small, lacking petals but with 5 pinkish to greenish-white, membranous winged sepals, stalkless in the axle of each cluster of 3 spine-tipped bract-like leaves. At maturity, the brittle stem breaks at the top of the root and the whole plant is rolled and tumbled by the wind, dropping seeds with each bounce and turn. Seeds cone- or top-shaped, the broader end flattened or hollowed and with a small point in the centre, about 2 mm (1/12 in.) across and the same long; the coiled embryo being visible through the nearly transparent seed coat. Flowers from July to August.
Russian thistle occurs throughout Ontario, usually in coarse soils along roadsides, railroads, waste areas, and occasionally in pastures and fields on sandy soils. It is distinguished from most other plants by its spininess and nearly spherical shape and from other so-called "tumbleweeds" by the long, thin, needle-like leaves of the young plant, and by the short, bract-like leaves and extremely spiny nature of the older plant.
(Source: Ontario Ministry of Agriculture and Food, Publication 505, Ontario Weeds)
