Conradina canescens (Torr. & A. Gray ex Benth.) A. Gray — Overview

False Rosemary learn more about names for this taxon

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False rosemary (Conradina canescens) is a small woody perennial shrub, one of about 22 species in five genera known as the scrub mints.  The scrub mints evolved in the pine scrub or sand scrub habitats that dominated the Southeastern United States until about 12,500 years ago.  These habitats are now much reduced in scope, and imperiled by human development.  Genus Conradina consists of seven known species, five of which are listed as threatened or endangered.  The species have very localized distributions in the southeast, all in Florida except one (C. vertacillata), which is found in Tennesee. 

Of the seven closely related Conradina species, C. canescens is the most common and widespread.  It occurs along the Gulf coast between the very eastern corner of Mississippi and the western Florida panhandle.  As its name implies, it resembles rosemary (Rosmarinus officinalis), in that it has similarly shaped flowers, needle-like leaves adapted for dry environments, and minty scent but it is not used in the kitchen.  Both are members of the mint family (Lamiaceae), however rosemary has a European origin and the two are not closely related. 

False rosemary grows to about 1 meter (3 feet) in height, in upland, well drained, scrublands behind primary sand dunes and into oak or pine forests.  Its stems are highly branched, and have small, fleshy leaves (4-8 mm long).  It prefers to grow with open spaces between individual plants, and produces chemicals that deter the growth of grasses.  Pretty light blue/lavender flowers grow in bunches up to six to a branch.  The tube-shaped flowers have dark purple spots on the inside of the tube.  The flowers grow from a green sheath at the base (the calyx) which is generally covered with dense hairs.  Many bees and other insect pollinators visit the flowers.  False rosemary is an important part of the habitat for beach mice subspecies in Alabama and Florida.    

Conradina brevifolia (short-leaved rosemary), which occurs as a small disjunct population in central Florida (Polk, Highlands and Osceola counties), was included as part of C. canescens by several authors (Wunderlin 1982, 1998; Delaney and Wunderlin 1989; Chafin 1990 as cited by Edwards et al. 2006) based on morphological similarities.  Subsequent genetic analyses indicate that C. brevifolia is a distinct species from C. canescens, and in a different species grouping within the genus (Edwards et al. 2008).  However this incorrect relationship persists in some web literature (e.g. Wunderlin 2008).  Distinguishing these species is crucial for policy decisions to provide protection for those that are endangered, but it can be difficult this genus is thought to have diversified very recently. 

Recently some populations of Conradina species were found in sheltered, shady, inland environments of Santa Rosa county in western Florida.  Considerably less hairy than nearby C. canescens, they were considered a potentially separate species.  Genetic analysis, however, finds these to indeed be C. canescens, which apparently can grow thicker hair to protect them when growing in harsher environments exposed to more wind and sun.

Conradina canescens is also known as minty-rosemary, blue-sage, and hairy rosemary.

(Brazis 2010; Edwards et al. 2006; Edwards et al. 2008a; Edwards et al. 2008b; Edwards et al. 2009; Fischer et al. 1989; Frater and Monello 2011; Kral and McCartney 1991; NatureServe 2015; Wunderlin 1998; Wunderlin and Hansen 2008)


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