Author
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Cane, James |
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Submitted to: Western North American Naturalist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/20/2004 Publication Date: 7/1/2005 Citation: Cane, J.H. 2005. Pollination needs of arrowleaf balsamroot, Balsamorhiza sagittata (Heliantheae: Asteraceae). Western North American Naturalist. 65(3):359-364. Interpretive Summary: Arrowleaf balsamroot 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 pollination experiments, this species was found to set no seed without pollinators. It is self-fertile, but sets more seed when outcrossed or visited by native bees. Seed production was not pollinator limited where it was studied. For two species of native cavity-nesting bee that obtain most of their pollen from balsamroots and their close relatives, Wyethia, minimum stocking densities are estimated at 120 females per acre to achieve thorough flower visitation in cultivated seed production fields. 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. |
