Abstract

Leitneria floridana Chapman (Florida corkwood) is native to the southeastern and south-central United States. This rare shrub has been cultivated north of its natural habitats. However, the cold hardiness of the species, and potential differences in hardiness among geographical provenances, have not been established. Our objective was to determine midwinter cold hardiness of stem segments from indigenous plants in Texas and Missouri, and from plants that had been cultivated for many years in northern Illinois, but were originally native to Missouri and Arkansas. After exposure to controlled low temperatures, the cortex and phloem were stained with 2,3,5-triphenyltetrazolium chloride (TTC) and compared with discoloration of the same tissues to determine midwinter cold hardiness. The two assays correlated positively, and marked provenance differences in cold hardiness were found. The estimated temperature at which 50% of stems were injured (T₅₀) was ≈ −20C (−4F) in December and−10C (14F) in January for samples from Texas. The estimated T₅₀ for stems from Missouri and Illinois was at or below the lowest temperature tested [−35C (−31F) in December and-60C (−76F) in January]. Stems from cultivated plants in Illinois and from plants indigenous to Missouri were similarly hardy within the range of temperatures used. Autumnal acclimation and vernal deacclimation of L. floridana remain uncharacterized, but midwinter cold hardiness of L. floridana seems sufficient to permit its use north of its natural habitat. Substantial provenance differences in cold hardiness should be considered when selecting plants for landscaping outside the native range of L. floridana.