Attractive Plants for Minimally Irrigated Landscapes in Colorado

In a plant taxa evaluation program conducted in conjunction with Plant Select® (http://plantselect.org/), almost 100 plant taxa have been evaluated over a two- to four-year growing period at Colorado State University’s W.D. Holley Plant Environmental Research Center.  The evaluation area was designed with two irrigation zones so that each taxa could be evaluated for its response to limited amounts of irrigation.  So that meaningful information pertaining to plant growth and survival could be obtained for each taxa, ten plants of each taxa were planted in each of the two irrigation zones.  In order for a plant taxa to gain access into the Plant Select® program, it must meet specified criteria, including: ability to grow in a broad range of garden situations in the Central Rocky Mountain Region, possess resistance to pests, thrive when grown under low water conditions, provide a long season of beauty in the garden, be non-invasiveness, possess capability of being mass produced, possess longevity in containers, and be fairly easy to propagate using basic propagation techniques.  Not all plant taxa that are in the evaluation program possess all the necessary requirements for acceptance into the Plant Select® program.  However, several taxa exhibited remarkable ability to not only survive, but to thrive when receiving only 39.1, 31.2, 41.9, and 23.1 cm of precipitation annually for 2009, 2010, 2011, and 2012 respectively.  Although the area received supplemental irrigation in all four years, irrigation amounts were not measured until the 2012 growing season.  Plants growing the in Minimal Water Zone received only about 4,542 mL of supplemental water the 2012 growing season. Seventy percent of the Penstemon wilcoxii planted in 2009 were still alive as of August 16, 2012.  One hundred percent of the Allium altaicum, Globularia punctata, and Sanguisorba tenuifolia; and 90% of the Penstemon fruticosus and Salvia multicaulis planted in 2010 were still alive as of August 16, 2012.  One hundred percent of the Centaurea bella, and 80% Tetraneuris scaposa (formerly Hymenoxys scaposa) planted in 2011 were still alive as of August 16, 2012. These plant taxa that can survive with little or no supplemental irrigation should be considered for planting in semi-arid areas and especially in areas where supplemental irrigation may not exist.