3. Croton L. (croton)

Plants annual (perennial herbs, shrubs, or trees elsewhere), monoecious or dioecious (in C. texensis), taprooted, with the sap clear (somewhat colored but not milky elsewhere), pubescent with branched or stellate hairs, these sometimes with branches more or less fused and then appearing as minute, scurfy, peltate scales; stinging hairs absent. Stems usually solitary, erect or ascending, unbranched or more commonly branched, sometimes from near the base. Leaves alternate but sometimes appearing opposite or whorled because of stem portions with very short internodes, sessile to long-petiolate, the petiole sometimes with 1 or 2 large, saucer-shaped glands at the tip, attached at the base of the nonpeltate blade. Leaf blades linear to nearly circular, tapered, angled, or rounded at the base, rounded or angled to tapered to a bluntly or sharply pointed tip, the margins entire or nearly so (regularly toothed in C. glandulosus), usually pinnately veined (sometimes only the midvein apparent). Stipules absent (in C. michauxii and C. willdenowii) or usually not apparent at flowering, then either minute (less than 1 mm long), lanceolate to ovate, tan scales that are shed early or small glandular dots that are obscured by the pubescence. Inflorescences terminal, axillary, and/or from the stem branch points, appearing as short, dense, spikelike racemes or dense clusters, the staminate and pistillate flowers variously positioned, each flower usually with an inconspicuous, short, slender bract (often threadlike, brown, and shed before flowering). Flowers with a nectar disc, this entire or with lobes equal to the number of calyx lobes. Staminate flowers with the calyces usually deeply 5-lobed, corollas of 5 petals (except in C. texensis) about as long as the calyx, the 5–20 small stamens (more elsewhere) with the filaments free. Pistillate flowers with the calyces usually deeply 5–12-lobed, corollas highly reduced or absent, the ovary with 1–3 locule(s) and 1 ovule per locule, the 1–3 style(s) free (or in some 3-styled species fused at the very base), each deeply 2-lobed, the lobes sometimes lobed again or branched. Fruits unlobed or slightly 3-lobed (circular in cross-section or nearly so), dehiscent except in C. michauxii and C. willdenowii. Seeds nearly spherical to oblong-ovoid or ovoid, the caruncle absent or a small, light-colored knob at the end adjacent to the attachment point, the surface smooth and often shiny, yellowish brown or reddish brown to dark brown, sometimes mottled. More than 800 species, nearly worldwide, but most diverse in tropical and subtropical regions.

The taxonomy and phylogeny of this large and morphologically variable genus still requires much further study. As noted by Webster (1967), for its size Croton contains surprisingly few species of economic importance. The common houseplants with brightly colored variegated leaves referred to as croton actually are Codiaeum variegatum (L.) A. Juss., a paleotropical member of the family not particularly closely related to the true crotons. The seeds of the Asian Croton tiglium L. are the source of croton oil, which has uses similar to those of castor oil (see the treatment of Ricinus). The stellate hairs sometimes are shed easily when plants are handled and can cause eye irritation.