Technical Abstract: Arrowleaf balsamroot, Balsamorhiza sagittata (Pursh) Nutt, is a common, sometimes dominant, long-lived forb that flowers early in spring from the foothills to upper montane areas of the northern Rocky Mountains and Intermountain West. Public land managers desire its seed for rangeland rehabilitation. Through manual pollination field trials, the species was found to have a mixed pollination system. It is primarily xenogamous (46% of ovules yielded plump achenes) but partially self-compatible (31% of achenes were plump). Unvisited flowers formed virtually no mature achenes; only plump achenes contained seeds with endosperm. Freely-visited flowers in two populations produced as many achenes as thorough manual outcross pollinations, suggesting that seed production was not pollinator limited. For two species of Osmia bees that rely largely on Balsamorhiza and its close relative, Wyethia, for pollen, minimum stocking densities are estimated at 240 females/ha to achieve thorough flower visitation in cultivated seed production fields.