Irrigation Requirements for Seed Production of Five Lomatium Species in a Semi-arid Environment

Seeds of native plants are needed for rangeland restoration in the Intermountain West. Relatively little is known about the cultural practices required for seed production of these plants since they are mostly non-cultivated species. Irrigation trials were conducted for perennial Lomatium species over multiple years. Lomatium species were grown at the Oregon State University Malheur Experiment Station, Ontario Oregon received zero, 100, or 200 mm of irrigation per year. Seed yield responses were evaluated by regression over irrigation plus precipitation. In general the seed yields from the three species planted for a decade responded linearly or quadratically to irrigation. In order to improve the accuracy of irrigation water requirements, regressions were run on seed yield responses to irrigation plus precipitation during the previous spring, winter, and fall. Over multiple years Lomatium dissectum and L. triternatum seed yields were best estimated by a quadratic response to irrigation plus spring precipitation at 243 and 255 mm, respectively. Over multiple years Lomatium grayi seed yields were best estimated by irrigation plus precipitation during the fall, winter and spring at 358 mm. Two of the Lomatium species were grown for the last six years. The seed yields of Lomatium nudicaule did not respond to irrigation. Seed yields of L. suksdorfii responded linearly to irrigation in 2015.