No abstract

Hydrangeas are popular seaside plants; however, other than in anecdotal reports, there are no studies measuring their relative tolerance to salt spray. We examined response of ten cultivars and one subspecies of Hydrangea representing five species to foliar-applied salt solutions to recommend selections for seaside landscapes. Objectives were to determine whether there are differences in responses to salt spray among cultivars and species, and to determine whether varying concentrations of sodium chloride differentially damaged the plants. Plants were treated with a full-strength (ion concentration approximate to seawater) salt solution, a half-strength salt solution, or a control of tap water. Plants were rated after seven once-weekly applications based on percentage necrotic leaf area, an aesthetically and physiologically important symptom of damage. Cultivars of Hydrangea macrophylla and Hydrangea serrata were more tolerant of full-strength salt spray than cultivars of H. paniculata, H. anomala and H. arborescens. At half strength but not full strength, H. anomala ssp. petiolaris was most tolerant. Hydrangea macrophylla and H. serrata were the second most tolerant of half-strength applications. Hydrangea macrophylla or Hydrangea serrata should be planted where maritime salt spray will occur.

Oak (Quercus) hybrids were created using over 40 diverse parent species. The developed hybrids were used as stock plants and asexually propagated annually over four years. This was done to measure the effectiveness of a modified stool bed layering technique on diverse members of the oak genus, and this study is part of a long-term project to select superior urban-tolerant oak hybrids for introduction as named cultivars into the nursery industry. The number of shoots produced by a stock plant each year and the probability for those shoots to root were found to vary between different maternal parent species. Results suggest the shoots of the hybrids that are the progeny of rhizomatous shrub Quercus spp. are more likely to develop roots when propagated using the described technique. This article also identifies and describes in detail a reliable technique to clone oaks.

This study evaluated a diverse range of oak (Quercus) hybrids for tolerance to alkaline soils, which is a common site condition in urban landscapes that often limits the growth and longevity of many tree species. Different oak hybrids display varying severities of iron-deficiency induced leaf chlorosis when grown in a highly alkaline medium. Severity of leaf chlorosis was found to vary between different maternal parent species, with the results suggesting that hybrids with the maternal parents Q. macrocarpa (bur oak), possibly Q. muehlenbergii (chinkapin oak), and Q. ‘Ooti’ (ooti oak), are more likely to maintain healthy green leaf color when growing in a highly alkaline medium. These findings suggest that breeders interested in developing oak hybrids that are both cold-hardy and tolerant of alkaline soils should utilize these species in their crosses, and avoid Q. bicolor (swamp white oak), hybrids of which were generally found to be intolerant of alkaline soil. This study is one phase of a long-term project underway at Cornell University's Urban Horticulture Institute to select superior urban-tolerant cultivars of oak hybrids for future introduction into the horticulture industry.