Trichostema dichotomum L.

Blue Curls


CC = 6
CW = 5
MOC = 21

© SRTurner

Family - Lamiaceae

Habit - Annual forb with slender taproot.

Stem - Ascending to erect, to 50 cm, slender, bluntly 4-angled, densely pubescent with gland-tipped and nonglandular hairs.

Trichostema_dichotomum_stem.jpg Stem and node.

© SRTurner

Leaves - Opposite, simple, entire, petiolate or the uppermost leaves sometimes sessile. Blades 1.5-6.0 cm long, mostly 5-25 mm wide, oblong to elliptic or ovate, angled or tapered at the base, bluntly or sharply pointed at the tip, minutely hairy, the surfaces moderately pubescent with minute, curved, nonglandular hairs, the undersurface also with inconspicuous sessile glands, the venation of a midvein and more or less evident, pinnately branching, secondary veins.

Trichostema_dichotomum_leaves.jpg Pressed leaves.

© DETenaglia

Trichostema_dichotomum_leaf1.jpg Leaf adaxial.

© SRTurner

Inflorescence - Inflorescences appearing terminal and axillary, usually as open, irregularly branched panicles with leaflike bracts that are smaller than the foliage leaves, the flowers paired at the nodes or in pairs of small, loose clusters or panicles, each with 3-7 flowers. Flowers becoming inverted as the fruits mature.

Trichostema_dichotomum_inflorescence.jpg Inflorescence.

© SRTurner

Flowers - Calyces 3-5 mm long at flowering, becoming enlarged to 5-9 mm at fruiting, zygomorphic, 2-lipped, the upper lip with 3 triangular lobes, about 3 times as long as the lower lip, which has 2 narrowly triangular lobes, the outer surface densely pubescent with a mixture of minute, gland-tipped and longer, nonglandular hairs, also with usually conspicuous sessile glands. Corollas 4-12 mm long, strongly zygomorphic, the tube funnelform, expanded in the throat, the upper lip with 4, shorter, similar, spreading to slightly inward-arched lobes, these blue to purplish blue, the lower lip with 1, much longer, spreading lobe, this abruptly spreading, usually white below the blue to purplish blue tip, the white portion spotted or mottled with blue to purplish blue. Stamens strongly exserted, the filaments 6-16 mm long, strongly arched downward, the anthers dark blue.

Trichostema_dichotomum_calyx.jpg Flower and calyx.

© SRTurner

Trichostema_dichotomum_flowers.jpg Flowers.

© SRTurner

Trichostema_dichotomum_flowers2.jpg Flowers.

© SRTurner

Trichostema_dichotomum_corolla.jpg Corollas.

© SRTurner

Fruits - Dry schizocarps, separating into usually 4 nutlets, these 1.5-3.0 mm long, yellowish brown to dark brown, glabrous.

Trichostema_dichotomum_fruits2.jpg Fruiting calyces.

© SRTurner

Trichostema_dichotomum_fruits.jpg Fruits.

© SRTurner

Flowering - August - October.

Habitat - Glades, openings of dry forests, bluff tops, sand prairies, usually on acidic substrate.

Origin - Native to the U.S.

Lookalikes - Trichostema setaceum

Other info. - This distinctive plant occurs in glades in the eastern half of Missouri's Ozarks. Its larger distribution extends from Missouri southward and northeastward, into the New England states and Canada. It is not massively showy, but a close look will reveal the beautiful detail in the flowers. The "curls" of the common name refers to the long, arching filaments. Although this is feature is highly characteristic, it is not unique to this species. A lookalike is T. setaceum, which has very similar flowers but leaves which are much narrower and lack evident lateral venation.

Trichostema dichotomum grows well from seed and makes for an interesting garden subject.

Photographs taken at Umstead State Park, NC., 9-22-02, and off Lee Rd. 54, Auburn, AL., 8-30-05 (DETenaglia); also at Don Robinson State Park, Jefferson County, MO, 08-23-2010 and 9-2-2021, and LaBarque Creek Conservation Area, Jefferson County, MO, 09-09-2012, 09-24-2014, and 08-27-2018 (SRTurner).