Moore, K.A., A.L. Shober, E. F. Gilman, C. Wiese, S.M. Scheiber,  M. Paz and M.M. Brennan

Posttransplant growth of container-grown wild coffee, copperleaf, and orange jasmine is affected by irrigation frequency

The survival of shrubs planted into the landscape depends on sufficient irrigation during the establishment period.  Few studies have investigated the effect of irrigation frequency on the post-transplant growth of landscape shrubs.  We conducted two studies in USDA hardiness zone 10b over a 2-year period in which we compared canopy growth index (GI), root extension to canopy spread ratio, canopy dry weight, and root dry weight of shrubs irrigated at different frequencies.  In the first experiment,  wild coffee (Psychotria nervosa) and orange jasmine (Murraya paniculata ‘Lakeview’ ) shrubs were planted in Sept. 2004, Dec. 2004, Mar. 2005, and June 2005 and irrigated for 28 weeks after planting (WAP) every 2, 4, or 8 d with 3 L of water per irrigation event.  In the second experiment, copperleaf (Acalypha wilkesiana ’Macafeeana’) and orange jasmine shrubs were planted in Sept. 2005, Dec. 2005, Mar. 2006, and June 2006 and irrigated for 28 WAP every 1, 2, or 4 d with 3 L of water per irrigation event.  Canopy GI and root extension to canopy spread ratio were determined at 28, 52, and 104 WAP.  The entire canopy and roots were harvested 52 and 104 WAP to determine dry weight.  In expt. 1, wild coffee and orange jasmine plants irrigated every 2 d had greater GI than plants irrigated every 8 d at 28 WAP but GI was not different at 52 or 104 WAP.  Canopy dry weight at 52 WAP was greater for plants irrigated every 2 d than 8 d, but there was no difference at 104 WAP.  There was no difference in wild coffee or orange jasmine root dry weight or root extension to canopy spread ratio among the irrigation frequencies.  In expt. 2, there were no differences in GI, canopy dry weight, root dry weight or root extension to canopy spread ratio of copperleaf or orange jasmine irrigated every day compared to plants irrigated every 2 or 4 d.   From the data collected in these studies, it appears that irrigating wild coffee or orange jasmine every 8 d during the first 28 WAP limited canopy growth but not root development. However, after 52 WAP, rainfall events appeared to be sufficient to eliminate any initial effects from irrigation frequency.  Our data suggest that wild coffee, orange jasmine, and copperleaf from 3-gal containers can be successfully established in the landscape when irrigated with 3L of water every 4 d for the first 28 WAP.