On the Discovery of Eastern Leatherwood (Dirca palustris)

The existing scientific literature dates the discovery of Eastern Leatherwood (Dirca palustris L.) to the 1730s and assigns John Clayton, a plant collector in the Virginia Colony, and Dutch botanist Jan Frederik Gronovius as the discoverers. But Michel Sarrazin, an early Canadian naturalist, was apparently the first to report on this species in 1700. Moreover, he also sent a living specimen of leatherwood to France. This case reminds us that the earliest information on some North American species predates the Linnaean binomial name.La littérature scientifique courante attribue la découverte du bois de plomb (Dirca palustris L.) dans les années 1730 à John Clayton, un collectionneur de plantes dans la colonie de Virginie, et au botaniste hollandais Jan Frederik Gronovius. Cependant, le premier rapport sur cette espèce a été rédigé en 1700 par Michel Sarrazin, l’un des premiers naturalistes canadiens. En outre, il a envoyé un spécimen vivant de bois de plomb en France. Ce cas nous rappelle que les premières informations sur certaines espèces d’Amérique du Nord précèdent le nom binomial linnéen.

Cold Hardiness of the Rare Dirca occidentalis: Comparisons to Dirca palustris from Disparate Provenances

We determined the cold hardiness of Dirca occidentalis (western leatherwood) within its restricted natural distribution in northern California and made comparisons to Dirca palustris (eastern leatherwood) from northern (Iowa) and southern (Florida) provenances. Stems of western leatherwood were sampled twice while all or some plants were dormant (October 27 and December 8, 2004, respectively) and again on January 19, 2005, when flowering and incipient vegetative shoot growth of most plants had begun. Stems of D. palustris were sampled on the same schedule and on March 2, 2005 (Iowa and Florida) and April 13, 2005 (Iowa) such that the last sampling date coincided with flowering and incipient vegetative shoot growth. Lowest survival temperature was determined based on visual assessments of the viability of cambium and phloem of stems exposed to progressively lower temperatures in a freezer. Lowest survival temperature of western leatherwood was −6 to −3C (21 to 27F) regardless of date. Eastern leatherwood accrued hardiness through mid-winter and then deacclimated; minimal lowest survival temperature of eastern leatherwood was −33C (−27F) in Iowa and −17C (1F) in Florida. The minimal cold hardiness of western leatherwood is consistent with its natural distribution in specialized niches within a Mediterranean climate. Unless western leatherwood accrues increased hardiness when planted where winters are harsh, its horticultural use will be restricted to areas with mild winters. In contrast, widespread use of eastern leatherwood is feasible if production challenges are resolved and selections from climatically appropriate provenances are used.