Irrigation Requirements for Seed Production of Five Lomatium Species in a Semiarid Environment

Seeds of native plants are needed for rangeland restoration in the Intermountain West. Many of these plants are rarely cultivated and relatively little is known about the cultural practices required for their seed production. Irrigation trials were conducted for five perennial Lomatium species over multiple years. Lomatium species grown at the Oregon State University Malheur Experiment Station, Ontario, OR received 0, 100, or 200mmof irrigation per year. Seed yield responses to irrigation were evaluated by linear and quadratic regression. In general, seed yields from the three species grown for 10 years responded linearly or quadratically to irrigation. To improve the accuracy of estimated irrigation water requirements, regressions were also run on seed yield responses to irrigation plus precipitation during the previous spring; spring and winter; and spring, winter, and fall. Over multiple years, Lomatium dissectum (Nutt.) Mathias & Constance and L. triternatum (Pursh) J.M. Coult. & Rose seed yields were best estimated by a quadratic response to irrigation plus spring precipitation with highest yields at 243 and 255 mm, respectively. Lomatium grayi (J.M. Coult. & Rose) J.M. Coult. & Rose seed yields were best estimated by a quadratic response to irrigation plus precipitation during the fall, winter, and spring with highest yields at 358 mm. Two of the Lomatium species were grown for the last 6 years. The seed yields of L. nudicaule (Pursh) J.M. Coult. & Rose did not respond to irrigation. Seed yields of Lomatium suksdorfii (S. Watson) J.M. Coult. & Rose responded linearly to irrigation in 2015.