Sida 17: 565. 1997 ,.
Trees, to 10 m. Stems armed, glabrous or glabrate. Leaves deciduous; petiole 3–7 mm, glabrate; blade (lustrous dark green adaxially), elliptic-ovate, 34–69 × 15–32 mm, base attenuate to cuneate, margins plane, apex rounded to obtuse, abaxial surface densely sericeous (hairs silvery), venation obscured by hairs, adaxial surface glabrous, midrib flat, marginal vein absent. Inflorescences 6–20-flowered. Pedicels 4–5 mm, velutinous (hairs silvery white to tawny). Flowers: calyx 1.6–2.4 mm diam.; sepals 5(–6), 1.9–2.6 × 0.9–1.9 mm, silvery-sericeous; petals 5(–6), white, median segment elliptic to ovate, 1.7–2.1 mm, lateral segments lanceolate, 1.6–2 mm; stamens 5(–6), 1.9–2.4 mm; staminodes deltate, 2–2.2 mm, minutely erose; anthers sagittate, 0.9–1.3 mm; pistil 5(–6)-carpellate; ovary 5(–6)-locular, 1.5–1.8 mm, velutinous; style 1.4–1.5 mm. Berries shiny black, oblong to ovoid, 10–13 mm, glabrate. Seeds 9–10 mm.
Phenology: Flowering Jul–Aug.
Habitat: Forested hardwood hammocks on calcareous sandy soils, shell middens, lime sinks
Elevation: 0-200 m
Of conservation concern.
Sideroxylon alachuense is characterized by leaves that are green and lustrous adaxially and densely silvery- sericeous abaxially. T. D. Pennington (1990) did not account for S. alachuense. This species has been included previously within S. tenax (A. Cronquist 1945c) and S. lanuginosum. Sideroxylon alachuense is most similar to S. tenax; Anderson enumerated significant differences between these species in twig color and indument, abaxial leaf surface indument color, and lengths of sepals, anthers, and styles. The straight, appressed, silvery hairs of S. alachuense are distinctive among North American species. There are 27 individuals known from four counties in Florida and one in Georgia.