Home: Species at Risk

Western Spiderwort

Western spiderwort (Tradescantia occidentalis) is the only species of Tradescantia native to Alberta. It is widely distributed in the central United States but enters Canada at only four locations: one in Alberta; one disjunct site in Saskatchewan, and two sites in Manitoba. In Alberta, western spiderwort occurs along the old dune fields east of Pakowki Lake and is restricted to the Dry Mixedgrass Subregion, an area extensively modified by agriculture with few native tracts remaining. The Alberta Natural Heritage Information Centre, because of its rarity in the province, ranks the species S1. Western spiderwort is designated as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 2000). 

The principal vegetation composition of western spiderwort sites appears to be typified by drought resistant grasses such as blue gama and needle-and-thread grass. Sand dunes exhibit a range of habitats from active dunes to stabilized sites with needle-and-thread grass and sand grass, a variety of low shrubs, primarily buckbrush and prickly rose; tall shrubs, mainly choke cherry and silverberry, and trees, including clones of aspen and scattered plains. 

Western spiderwort normally flowers from May to July. Each flower lasts only one day. The plant reproduces through seeds an by vegetative propagation. Western spiderwort is very dependent on moisture levels. There are many other indigenous species of plants that western spiderwort may be confused with in its natural habitat in southeastern Alberta. 

Reprinted from Alberta Wildlife Status Report No. 31 (2001), with permission from Alberta Sustainable Resource Development.

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