Vascular Plants of Williamson County

Croton texensis [Euphorbiaceae]
Texas croton, skunkweed

Croton texensis (Klotzsch) Müller Arg., Texas croton, skunkweed. Annual, taprooted, 1–stemmed at base, with a spreading, flexible lateral branch from each node above midplant, erect, 40—85 cm tall; dioecious; shoots with only cauline leaves, mature foliage grayish green from reflective shieldlike (peltate), stellate hairs having a clear center (not aging brownish), unexpanded leaves whitish with dense pubescence, each hair with mostly 10—15 rays from top of stalk fused at base and forming a plane or bowl; pleasantly aromatic; latex clear.

Stems

Stems cylindric, to 4.5 mm diameter, flexible and tough, branch axes wiry, light yellowish green, stellate–pubescent, lower stem lacking leaves when flowering begins, aging reddish orange with scattered stellate hairs later appearing glabrous after outer portion peels in sheets (exfoliate).

Leaves

Leaves helically alternate, simple, petiolate, with stipules; stipules 2, attached to base of petiole, hairlike and inconspicuous, < 0.3 mm long, tannish, early–deciduous; petiole cylindric, to 14 mm long, green with ± dense stellate hairs; blade linear–lanceolate, < 30—62 × < 5—15 mm, ± rounded and symmetric at base, entire, acute at tip, pinnately veined with midrib sunken on upper surface and raised and other principal veins slightly raised on lower surface, typically 3–veined at base, ± green but uniformly stellate–pubescent.

Staminate inflorescence

Staminate inflorescence raceme, terminal and axillary, terminal array usually cymelike of 3 racemes commonly with a subopposite pair of lateral racemes, each raceme several–flowered, in bud ± deltoid and densely whitish peltate–stellate pubescent; bract subtending lateral raceme leaflike but diminutive and folded upward, of upper lateral raceme mostly 4—5 mm long at the start of blooming and < inflorescence, of lower lateral raceme mostly 5—10 mm long and > inflorescence, whitish with dense pubescence, deciduous; peduncle slender and flexible; bractlet subtending pedicel linear, ca. 1 mm long, early–deciduous; pedicel 1—1.5 mm long increasing 2× during blooming then abscising from base.

Staminate flower

Staminate flower radial, 2—2.5 mm across; calyx deeply 5–lobed, hemispheroid, ± 1.5 mm long, densely stellate–pubescent on outer surface, cells of outer surface domed; tube ca. 0.5 mm long, green at base and white above; lobes rounded–ovate, ca. 1 × 1 mm, white, with stellate hairs on inner (upper) surface above midpoint; corolla absent; nectary disc reduced to 5 separate glands opposite sepals, the glands deltate, ca. 0.3 × 0.4 mm, greenish, thin; stamens (8—)11—12, free; filaments erect, exserted, 1.2—2 mm long, white, conspicuously villous to midpoint, the hairs appearing mostly unbranched; anthers basifixed, dithecal, 0.5—0.6 mm long, light yellow to white, longitudinally and sideways dehiscent; pollen light yellow; pistil absent.

Pistillate inflorescence

Pistillate inflorescence cyme, several–flowered, flowers on short pedicels, densely stellate–pubescent, the hairs with to 25 arms; bractlet subtending flower linear, to 2 mm long, deciduous; pedicel short increasing slightly in fruit.

Pistillate flower

Pistillate flower radial, 3—3.5 mm across; calyx deeply 5—6–lobed, green, stellate–pubescent; tube < 1 mm long; lobes erect, subequal (5) or conspicuously unequal (6), triangular, 2—3 × 1.5 mm (typically); corolla absent; nectary disc below and surrounding ovary, ringlike, irregularly lobed, upper margin free, yellow, thin; stamens absent; pistil 1; ovary superior, spheroid and weakly 3–lobed, ± 2.1 mm, green, covered with peltate–stellate hairs and having spaced, low projections more densely covered with hairs (“warty”), 3–chambered, each chamber with 1 ovule attached to center; styles 3, ascending, tentaclelike with 2 forks to form ca. 6 terminal branches per style (= 18 per pistil), to 1.5 mm long, white, the first fork near the base and second fork at midpoint, with stellate hairs to below the second fork, papillate and stigmatic (presumably) on remaining faces.

Fruit

Fruit capsule, 1—3–seeded, weakly 3–lobed, 5.5—6.5 mm wide and tall, ± schizocarpic by dehiscing along septa and splitting from central axis into 3 segments, covered with stellate hairs (abscising) and not apparently warty when raised tufts of hairs lost.

Seed

Seed with fleshy appendage (caruncle), ovoid and often 2–sided, 4—4.5 × 3—4 mm (including caruncle), smooth, brown with rectangular patches of tannish white and low convex inner side mostly tannish white occasionally with brown patches, outer side well rounded and puberulent above midpoint, inner side with groove separating lateral faces; caruncle caplike and tightly covering tip of seed drying to inner side not visible from outer side, when fresh ca. 1 mm long, whitish.

A. C. Gibson