Prairie Spiderwort

All of the chromosome counts cited by E. Anderson (1954) for this species are attributable to Tradescantia occidentalis var. occidentalis.

Herbs, erect or ascending, rarely rooting at nodes. Stems 5--90 cm; internodes glaucous, glabrous. Leaves spirally arranged, sessile; blade linear-lanceolate, 5--50 ´ 0.2--3 cm (distal leaf blades equal to or narrower than sheaths when sheaths opened, flattened), apex acuminate, glaucous, glabrous. Inflorescences terminal, often axillary; bracts foliaceous. Flowers distinctly pedicillate; pedicels 0.8--3 cm, glandular-puberulent, rarely glabrous or glabrescent; sepals 4--11 mm, glandular-puberulent, usually with apical tuft of eglandular hairs, occasionally with scattered eglandular hairs among glandular, rarely glabrous or glabrescent; petals distinct, bright blue to rose or magenta, broadly ovate, not clawed, 6--16 mm; stamens free; filaments bearded. Capsules 4--7 mm. Seeds 2--4 mm.

Tradescantia virginiana Linnaeus var. occidentalis Britton in N. L. Britton and A. Brown, Ill. Fl. N. U.S. 1: 377. 1896

Tradescantia occidentalis, the prairie spiderwort or western spiderwort, is a plant in the dayflower family, Commelinaceae. It is common and widespread across the western Great Plains of the United States, as well as in Arizona, New Mexico, southern Utah, and Sonora, but is listed as a threatened species in Canada.

Like in a few other species of Tradescantia, the cells of the stamen hairs of Western spiderwort are normally colored blue, but when exposed to neutron radiation or other forms of ionizing radiation, the cells mutate and change color to pink. Thus the plant can be used as a bioassay for radiation.