Perennial plants (flowering in the first year from a slender taproot but eventually producing a woody taproot and woody, branching caudex) with pinnatifid basal and lower cauline leaves with long petioles persistent after the blades are gone (Figs. 7–19, Figs. 7–14 showing increasing development of a woody caudex). The pinnatifid leaves usually are crowded along 1–4(–8) cm of the stem base. Such plants, which I have annotated at various times and referred to (e.g., Nesom 2006) as the "Erigeron accedens form" of E. divergens, occur widely in Arizona and into adjacent
In Arizona, Erigeron incomptus occurs at (1350–)2000–5000(–rarely to 6500) feet and flowers March–June, continuing sparsely into August and very rarely to October and November. Elsewhere it has been documented in flower as early as February and at elevations as low as 600 feet.
Erigeron incomptus occurs sympatrically with annual forms. Most chromosome counts of E. incomptus have been triploid, and apomictic seed production associated with triploidy in Erigeronprobably contribute to its apparent morphological stability. Vouchers for triploid counts are shown in Figs. 16–19; a voucher for a tetraploid count is cited below from Doña Ana Co., New Mexico. The coherent geographical distribution in Arizona suggests that at least the triploids of E. incomptus had a single origin.
It seems likely that E. incomptus is of hybrid origin, the parental combination speculative. Whether the California and Baja California plants are long-distance disjuncts or of independent origin is not clear –– typical E. divergens occurs in both areas but both areas are outside of the range of E. flagellaris and E. tracyi, which presumably are the closest relatives of E. divergens and among potential parents (if E. incomptus is a hybrid). Basal leaves in California and Baja California populations are unlobed but otherwise similar in morphology and placement to those eastward.
Plants apparently intermediate between Erigeron incomptus and annual forms are shown in Figs. 5–6. If they indeed are genetic intermediates, it suggests that tetraploid E. incomptus (capable of crossing with typical E. divergens) probably is more common than indicated by the limited sampling of chromosome numbers. Otherwise, it is possible that such plants are triploid E. incomptusshowing further variation in the range of its expression.
The epithet incomptus (Latin, unadorned) alludes to the ray floret ligules much reduced in size (as in the type collection) –– similar floral variants are known from other Erigeron species, including E. flagellaris.