Carya Species for Use in the Managed Landscape: Predicted Drought Tolerance

Impressive ornamental features including exfoliating bark and golden fall color are among the reasons why hickories [Carya (Nutt.)] are sought after by horticulturists. Their potential for application in the green industry continues to grow as producers and consumers in the United States become more interested in adopting native plants; however, an absence of knowledge that defines which species are tolerant of abiotic stresses in the landscape limits their use. If production of stress-tolerant hickories increases, they could be used to diversify urban forests and may bolster the resiliency of managed landscapes. We examined the predicted leaf water potential at the turgor loss point to estimate drought tolerance among several species of hickories and pecans adapted to growing in northern climates in the United States. Our hypotheses were that because some bottomland habitats experience seasonal drought in addition to flooding, taxa adapted to these sites may be more drought tolerant than previously assumed, and that the degree of drought tolerance would be variable within species and populations. Predicted mean leaf turgor loss measured in summer across species was 23.38 MPa. Kingnut hickory [Carya laciniosa (F. Michx.) Loud.] exhibited the lowest mean summer leaf turgor loss point 23.64 MPa), whereas pignut hickory [Carya glabra (Mill.) Sweet.] exhibited the highest (23.20 MPa). Provenance of trees studied influenced estimated drought tolerance of C. laciniosa. Variability between individual trees within each species was observed, suggesting clonal selections of each taxon can be made for droughtprone landscapes. The results of this work imply that all the species studied are at least moderately drought tolerant and should be considered for planting in managed landscapes. Further, species often associated with riparian habitats may exhibit substantial tolerance to drought and should not be excluded from use on drought-prone sites.