This small tree is widely scattered across southeastern states, especially on dry calcareous soils. There is much variation that needs further study; the more northern C. pumila Pursh appears closely related and would have priority if combined;. C. tenuifolia has often been confused with laevigata or occidentalis but hybrids may not generally occur (Hayes et al. 2022). Previously suspected hybrids with occidentalis in Ky. are up to 5-9 dm dbh and 15-20 m tall. but these are referrable to C. laevigata var. smallii (JC from ANDE, FAYE). C. tenuifolia is a triploid (2n = 30), probably resulting from hybridization of laevigata and occidentalis, and then generally reproducing through apomixis (Y, Hayes 2019, Hayes et al. 2022) But artificial pollination by other species is still possible (A. Whittemore in Y and unpublished); "some puzzling forms found in the wild may have originated by pollination of apomictic C. pumila [tenuifolia] by pollen from C. laevigata or C. occidentalis" (Y). Most tenuifolia from Ky. fits the relatively pubescent and coriaceous-leaved var. georgiana (Small) Fern. & Schub., but further assessment of that taxon is needed. Using older treatments, some plants with more serration have been identified as C. occidentalis var. pumila (Pursh) Gray (or C. pumila var. deamii Sarg,), which has a more northern ranges (to N,D. Que and New England). Whittemore (Y) has distinguished pumila (sensu lato) from laevigata as follows: mature trees mostly 3-8 (up to 12?) m tall (versus 8-30 m); trunk usually smooth over most surface (versus usually with corky warts or ridges); sun leaves usually pale green to glaucous below (versus bright green); pedicels and twigs usually short-pilose to glabrate (versus largely glabrous except for sparse longer hairs). Other authors (F, Cr) have emphasized the relatively small size of leaves in tenuifolia, with less serration, more pubescence, and less elongated shape on fertile shoots (blade L/W = mostly 1.6-2 versus 2-2.3), but these characters may be unreliable (Y). C. laevigata often has small broad entire leaves with similar shape to tenuifolia. No single character seems to be consistently diagnostic.