Flora of North America species comparison

Froelichia floridana ranges from broad-leaved stout herbs surpassing 1 meter in height to much-branched plants forming bushes to 2 meters in diameter and single-stemmed, erect herbs 1 dm in height. Much of the variation in the species has been difficult to ascribe to either geographic or ecologic differences and reflects inherent genetic variability and wide environmentally induced plasticity. Although specialists and taxonomists have implied the existence of well-delineated morphologic taxa with a strong geographic correspondence, this is not always true, and, in fact, one encounters typical specimens of any given variety sporadically throughout the range of the species.

Some variability in Froelichia floridana is clearly attributable to geography, principally in terms of general morphologic trends. There is a cline toward long, narrow, almost linear leaves as one moves east along the Gulf Coast and into Florida. This would culminate in the little-known var. pallescens Moquin-Tandon, a linear-leaved form (leaf length more than eight times width) from peninsular Florida. Additional variation ascribable to geography is observed in plants traditionally included in F. drummondii, these being large, stout plants with broader leaves, more obtuse leaf apices, and more densely fulvous pubescence on the abaxial surfaces of leaves. Plants of this form are generally restricted south of the Brazos River and continue to the southern extent of the range in Kenedy County, Texas. Further work examining this variation using micromorphology or molecular markers may elucidate a reliable means to identify intraspecific taxa within F. floridana.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The current range of Froelichia gracilis is due in large part to its introduction via railroads during the past 100 years, and the majority of records for the species east of the Mississippi River occur on or near railroads. S. F. Blake (1956) discussed this eastern spread of the species. Froelichia gracilis is considered a minor invasive weed in the Northeast; its adaptation to open sandy or gravely soils will restrict its spread to open sites with poor soil.

In regions where their ranges overlap, Froelichia gracilis may hybridize with F. floridana. Plants with intermediate form from Texas and the Midwest have been noted. Suspected hybrids appear closest in habit to F. gracilis and will generally key to that species. Floral structure will be intermediate and variable; the branching will be typically less than in F. gracilis and present distal to the base.

(Discussion copyrighted by Flora of North America; reprinted with permission.)