Native Plants Journal

With about half the amount of water, subirrigated Metrosideros polymorpha Gaud. (Myrtaceae) grown 9 mo in a greenhouse were similar to those irrigated with an existing fixed overhead irrigation system; moss growth was about 3X greater in the fixed overhead system after 3 mo. Moss growth was affected by the rate of preplant controlled release fertilizer added (more fertilizer, less moss) and moss maturity, quantified as presence or absence of sporangia, was slowed with subirrigation. About 5 g nitrogen (N) leached per m2 (0.02 oz/ft2 ) of greenhouse bench under the fixed irrigation system, whereas none was lost from subirrigation. Besides Metrosideros macropus, the USDA Forest Service and Purdue University are evaluating subirrigation for nursery production of other species. To date, the results indicate subirrigation may be a useful technique for growing native plants with large canopies where conventional irrigation systems are less effective, or where water use or other environmental concerns are paramount.