Geranium 'Gerwat'

Summary

UC Davis is located in Davis, California, this site has a silty clay loam soil and plants are irrigated with potable water. More information about the field sites is located in the Nuts & Bolts section.

This hardy geranium cultivar has been in the trade for years, and was a recipient of the Royal Horticultural Society Award of Garden Merit (AGM) in 2006.  In our hot climate, mortality during the establishment year meant we entered the second year with uneven numbers across treatments, which made really meaningful statistical comparison impossible. Each treatment lost one additional plant during the deficit irrigation season, leaving us at the end of the trial with 4 plants on 80%, 4 plants on 60%, 5 plants on 40%, and 2 plants on 20% of ET₀.  The average size reached by these plants was 3’ wide (91.2 cm) and 16.7” wide (42.3 cm).  All treatments flowered at some level from April through October with the most abundant flowering in June and July, and the highest annual flowering rating on the highest irrigation treatment.  All treatment levels were pest and disease free.  The greatest vigor and overall appearance ratings were on the two highest irrigation levels, with ratings only falling under the acceptable 3.0 level in August on the 20% treatment, in September for the 60% and 40% treatments, and October for the 80% treatment.  Since this is a tender perennial that dies back in fall anyway, these are not terribly surprising or disappointing findings.  What is significant is that it rated as well as it did on our spare irrigation regimes in the full sun in our harsh site.  We feel that this plant may best be suited to afternoon shade in interior sites where it would provide acceptable appearance on twice monthly deep irrigation.