The perennial Juncus of section Poiophylli in the Canadian prairie provinces

Specimens of the perennial Juncus of section Poiophylli in major Canadian herbaria were examined to clarify the status of the group in the prairie provinces and to evaluate diagnostic characters. Six taxa are recognized. Of these, Juncus interior, which occurs in the prairie region of southern Manitoba, southern Saskatchewan, and southern Alberta, has been largely overlooked. Juncus confusus, frequently confused with Juncus tenuis, is confined to southwestern Saskatchewan and southern Alberta. Juncus dudleyi is widespread and common throughout the three provinces, whereas Juncus vaseyi is widespread but clearly less common in the prairie region than in the more northerly boreal forest areas. Juncus tenuis, also found mostly in the boreal forest region, is apparently frequent only in central Saskatchewan and is rare elsewhere. Juncus compressus is recently adventive in southern Manitoba. Reports of Juncus gerardii are discounted and J. oronensis is considered to be a rare hybrid. The diagnostic value of characteristics of the leaf auricle is affirmed through correlation with other distinctive characters such as the shape of the bracteole apex and bracteole length and to a lesser extent with anther length and seed length. Although seed lengths differ between J. dudleyi and J. interior, there is sufficient overlap in the prairie provinces to make this character unreliable for identification. Other taxonomic characters are discussed and an illustrated key and distribution maps are included.