The 2011 ASHS Annual Conference

Native wildflower seed is needed to restore rangelands of the Intermountain West. Commercial seed production is necessary to provide the quantity of seed needed for restoration efforts.  A major limitation to economically viable commercial production of native wildflower seed is stable and consistent seed productivity over years. In native rangelands, the natural variations in spring rainfall, soil moisture, and other factors result in different seed productivity from year to year.  For commercial seed production in an arid environment, supplemental irrigation may be often required for successful flowering and seed set because soil water reserves may be exhausted before seed formation.  Thirteen native forb species were tested for their seed yield response to three low rates of drip irrigation at the Oregon State University Malheur Experiment Station in eastern Oregon. Drip tape was installed 0.3 m deep and 1.52 m apart. Four rows of seed were drilled 0.76 m apart so that the seed were alligned equidistant from a drip tape. Each plot of each specie consisted of four rows of plants with the middle two harvested for seed yield. Each irrigation treatment consisted of four irrigations that were applied approximately every 2 weeks starting independently with the flowering of each forb species. The three irrigation treatments were a non-irrigated check, 25 mm per irrigation (100 mm/season), and 50 mm per irrigation (200 mm/season).  The total irrigation requirements for these arid-land species were low and varied by species.  The seed yields of Sphaeralcea parvifolia, S. grossularifolia, and S. coccinea and Penstemon acuminatus did not respond to irrigation.  Penstemon speciosus and Lomatium dissectum had quadratic seed yield responses to irrigation and required approximately 100 mm of irrigation.  Lomatium grayi, L. triternatum, and Eriogonum umbellatum responded quadratically to irrigation with optimum near 150 to 200 mm.  The other species tested had insufficient plant stands to reliably evaluate their responses to irrigation. Species varied considerably in their longivity (2 to 6+ years) and delay to first seed set (1 to 4 years).