Croton michauxii G.L. Webster

Slender Rushfoil


CC = 8
CW = 5
MOC = 3
SRank = S1

© SRTurner

Family - Euphorbiaceae

Habit - Monoecious forb. Plant parts are moderately to densely pubescent with minute, peltate, scalelike trichomes (except on the upper surface of the leaf blades), these with a minute, raised, brown attachment point and a relatively slender, thin, white body, the slender, stellate extensions forming a noticeable fringe around the margins, this often slightly raised and thus providing a fuzzy appearance (especially on the fruits).

Stems - Ascending, to 40 cm, usually alternately branched, with scalelike trichomes as described above.

Croton_michauxii_stem1.jpg Stems and leaves.

© SRTurner

Croton_michauxii_stem2.jpg Stems and leaves.

© SRTurner

Leaves - Alternate, simple, sessile or very short-petiolate. Blades 1.0-2.5 cm long, linear, angled or short-tapered at the base, angled or short-tapered to a sharply pointed tip, the margins entire, the upper surfaces with moderate minute, non-overlapping, stellate hairs, the branches 0.2-0.3 mm long, the undersurface paler than the upper surface and bearing numerous scalelike trichomes.

Croton_michauxii_leaf1.jpg Leaf adaxial.

© SRTurner

Croton_michauxii_leaf2.jpg Leaf abaxial.

© SRTurner

Inflorescences - Axillary, mostly elongate, loose spikes with 2-4 pistillate flowers scattered toward the base and several staminate flowers toward the tip.

Flowers - Staminate flowers with the calyx deeply 5-lobed, 0.8-1.1 mm long; the petals 5, 0.6-1.0 mm long, white; the stamens 4-6. Pistillate flowers with the calyx 0.8-1.1 mm long at flowering, becoming very slightly enlarged at fruiting, 5-lobed; the petals absent; the ovary 1-locular, the 3 styles shallowly 2-lobed toward the tip.

Croton_michauxii_flowers.jpg Flowers.

© SRTurner

Fruits - Schizocarps 2.5-3.0 mm in length and diameter, elliptic to oblong-ovate in outline, slightly flattened, 1-seeded, indehiscent, thin-walled. Seeds 2.5-3.0 mm long, elliptic to oblong-ovate in outline, slightly flattened, lacking a caruncle.

Croton_michauxii_fruits2.jpg Fruits.

© SRTurner

Croton_michauxii_fruits.jpg Fruits.

© SRTurner

Flowering - July - September.

Habitat - Sand prairies, sand savannas, open, sandy, disturbed areas.

Origin - Native to the U.S.

Lookalikes - C. willdenowii.

Other info. - This wispy, wiry species is inconspicuous and very easily missed. The only aid to finding it is that it tends to grow in areas of open sand supporting nothing else. The wispy nature, scaly appearance of the stems and leaves, tiny white flowers, and tiny ovoid fruits are all clues to the plant's identity. The biggest clue of all is habitat, since the plant is always found in sandy substrate. Because of its strict habitat requirement, the plant is rare in Missouri, being entirely restricted to sand prairie areas of the Mississippi Lowlands Division. It is considered critically imperiled in Missouri. However, it is somewhat more prevalent in states to our south, particularly in regions near the Gulf Coast.

The species has been subdivided, with the plants described here corresponding to var. michauxii. The other variety, var. ellipticus, is far more common and has long been called C. willdenowii.

Photographs taken at the racetrack sand prairie, Scott County, MO, 8-30-2011, and at Sand Prairie Conservation Area, Scott County, MO, 8-8-2022 (SRTurner).