Irrigation Needs For Seed Production

Native wildflowers—or forbs— in the Intermountain West are well adapted to arid environments, and their water needs are usually satisfied by yearly precipitation in their native habitat. When producing wildflower seed commercially, growers must consider the habitat shift from native ecosystem to cropland and irrigate accordingly to the relatively low water needs of rangeland wildflowers. Because yearly precipitation will still primarily satisfy a large part of wildflowers’ water needs, seed growers should only supplement yearly precipitation to maximize seed production (Shock, et. al, 2013). Research done by the OSU Malheur Experiment Station has shown that drip irrigation offers benefits for wildflower seed production, including weed control and water conservation.

When choosing irrigation methods, it is important to analyze the differences in sustainability of irrigation systems. Buried drip irrigation systems, (subsurface irrigation, or SDI) are effective for water delivery and weed prevention. SDI reduces weed pressure by providing water to plants at depth; consequently, weed seeds at the soil surface have limited water to promote germination (Shock, Feibert, Saunders, Shaw, & DeBolt, 2007). Efficient irrigation was obtained by burying drip tape 12 inches (30.5 cm) below the planting soil surface and centered between plant rows for forb seed varieties (Parris, Shock, Feibert, & Shaw, 2010).

Water requirements for native wildflower seed production varies by species, growing location, growing season, spring rainfall, and soil moisture. Because of their environmental adaptations, including extensive and deep root systems, native wildflower plants are especially efficient in water usage and are highly drought tolerant (“Thorn Creek Native Seed | About,” n.d.). However, inadequate or excess moisture could stall flowering and prevent plants from abundantly producing seeds. In the Ontario, Oregon area, where the average rainfall is 10 inches per year, it is recommended that most species be watered 1-2 inches every 2 weeks upon flowering (U.S. Climate Data, 2010; Shock, Feibert, Saunders, Shaw, & Sampangi, 2011). For optimum seed production in Lomatium grayi, only 6-8 inches of supplemental water is suggested to be applied throughout spring and into early summer, receiving a total of approximately 16-18 inches of moisture per year. Typically, wildflowers require water treatments at an earlier time of the year than traditional row crops due to early emergence from dormancy in the late winter and early springtime followed by each flowering and seed set (Shock, Shock, & Feibert, 2012).

Furrow and sprinkler irrigation should be avoided on silt loam because prolonged soil moisture encourages the establishment of weeds and fungal pathogens at the soil surface. Native wildflowers cannot compete with weeds; fungal pathogens negatively affect the growth and health of wildflowers such as Penstemon acuminatus and Penstemon Spectabilis (Shock, Feibert, Saunders, Shaw, & Sampangi, 2011). Furrow and sprinkler irrigation can aggravate soil surface crusting, decreasing the chance of forb seedling emergence (Stevens, Jorgensen, Young, & Monsen, 1996). Drip irrigation can help minimize these complications in wildflower seed production.