The 2009 ASHS Annual Conference

Eriogonum corymbosum is a highly diverse species native to the Intermountain West with aesthetic and drought tolerance characteristics that make it desirable for low water or conventional urban landscapes. Since little is known about how its performance in irrigated settings, we investigated its range of water tolerance to frequent and no irrigation in a landscape setting. Out of 15 E. corymbosum accessions two were selected. These two were collected at notably different elevations and display dissimilar leaf morphologies. The two E. corymbosum accessions, along with Cornus sericea ‘Kelseyi’ as a drought-intolerant reference, were irrigated every three days, every three weeks, or no supplemental water added. Stomatal conductance and pre-dawn water potential were measured weekly. Prior anecdotal observations suggested that E. corymbosum is damaged or dies in very wet soils, but both accessions irrigated every three days showed no injury.  In late August 2008, non-irrigated, higher-elevation accession plants averaged substantially higher stomatal conductance (524 mmol m^-2 s^-1) than the non-irrigated lower-elevation accession plants (344 mmol m^-2 s^-1). Non-irrigated C. sericea ‘Kelseyi’ appeared to be water stressed, as it averaged 18 mmol m^-2 s^-1 over the same period. However, late August water potential measurements for both the E. corymbosum accessions and C. sericea ‘Kelseyi’ were not significantly different.  Plants of C. sericea ‘Kelseyi’ grew well under frequent irrigation, but non-irrigated plants of this species ceased transpiring under initial soil drying early in the season and showed considerable margin burn by season end. The two E. corymbosum accessions showed no visible signs of water stress, but differed considerably morphologically. The high elevation accession had much smaller blue-green leaves, in compared to the larger yellow-green leaves of the low elevation accession. These data suggest that morphological differences may be linked to physiological differences observed in E. corymbosum and both will be considered in selecting the best drought-tolerant accession for further cultivar development.