Abronia fragrans and Abronia elliptica are very similar plants.  They are recognized as two distinct species by Kartesz, the Flora of North America, and Weber, but they are combined into A. fragrans by Welsh in his 4th edition of A Utah Flora.   The most agreed upon characteristic that separates the two as distinct species is the shape of the seed:  A. fragrans fruits are (in Weber's words) "thick-walled, hard, the wings leathery , not folded together".  A. elliptica fruits are (again in Weber's words): "thin-walled, delicate, the wings not rigid or stiff, 2 of them folded together to form a groove".   FNA further indicates that the fruit of A. fragrans is arrowhead-shaped versus heart-shaped in A. elliptica.

    Welsh indicates that the species (A. fragrans) is "tremendously variable", and although he recognizes that others have separated A. fragrans into two species (or into subspecies) on the basis of fruit and other characteristics, he indicates that both types of fruit can be found in the same head.  Welsh, therefore, concludes that "the separation [into two species or subspecies] seems to be arbitrary and is not correlated with other features".

    A personal communication to me by Bob Sivinski (noted botanist with the New Mexico Forestry Division) indicates that at least one of the photographs below (second from the bottom) does show A. elliptica, not A. fragrans, as evidenced at least by the close spreading of plants, probably from underground roots.   Bob indicates that although "none of the floristic manuals say it, ... A. elliptica has branching underground stems in most cases - you just have to dig deeply to find them".  Welsh addresses this point: "Recognition of the occasional rhizomatous plants, which occur sporadically through the range of the species, at any taxonomic level seems unwarranted". 

    One further characteristic that is sometimes said to separate the plant into two species is the hairiness of the stems, leaves, and/or peduncles.  But I can find no agreement from one authority to another on these characteristics.

   Those breaking the plant into two species or subspecies only generally agree on the range.  Both Kartesz and FNA show A. fragrans as a plant of the eastern Colorado plains, eastern Wyoming, just a few western counties of Kansas and Nebraska, much of New Mexico, northern Arizona, and only San Juan County (the very southeast) of Utah.  FNA agrees with Kartesz except that it omits most of Arizona and includes almost all of Colorado.  The two are more in agreement on the range of A. elliptica: It is found, they claim, in northern Arizona, most of Utah (Kartesz says "all of Utah"), the northwest corner of New Mexico, and central and southwestern Wyoming.  Kartesz also places it in eleven counties in Idaho and three in Montana. 

    Although Kartesz and FNA indicate that Abronia elliptica is found in much or all of Utah (actually having Utah as its central core of distribution), the acknowledged expert on the flora of Utah, Stanley Welsh, states that there is no Abronia elliptica, nor Abronia fragrans variety elliptica, in his state; all of the plants, says Welsh, are Abronia fragrans.

    One final twist on all of this:  In Harrington's Manual of the Plants of Colorado (1964), Harrington indicates that A. fragrans grows in Colorado, but he does give two supspecies, A. fragrans elliptica and A. fragrans glaucescens, separated from each other and from A. fragrans on the basis of the hairiness of the plants.  Harrington also defines two other species, A. carletoni (which Kartesz indicates exists only in a few counties of New Mexico and western Texas) and A. salsa, (which Kartesz indicates is a synonym for A. elliptica).