Summary: Young trees, particularly those in Ellepots, are very susceptible to temperature fluctuations. In 2021, damage from frost and an extreme heat dome severely injured many of the young trees in our outdoor pot-in-pot planting. Trees killed or significantly damaged included the positive control, ‘Mahaleb’, the negative control, ‘Mazzard’, and the rootstock I was most interested in testing, ‘MaxMa 14’. Future studies like this should be completed in a greenhouse so the temperature can be controlled. In addition, we can rely on X-disease survey data to rule out rootstocks that are susceptible and symptomatic to X-disease infection. Based on my survey study, we should not include ‘K.6’, ‘Gi.12’, or ‘Gi.6’ in future studies. Data from WSU may have insights into the susceptibility of ‘K.5’ and ‘Gi.5’. I believe it would be more efficient and effective to focus on newer rootstock and more infrequently used rootstocks, like ‘MaxMa 14’.
