Calopogon tuberosus (L.) Britton, Sterns & Poggenb.

Grass Pink

Calopogon tuberosus plant2

Family - Orchidaceae

Habit - Perennial forb from undivided tuberlike corm.

Stems - Erect, to 60 cm, terete, green, glabrous, simple, single from the base.

Leaves - One well developed leaf per stem. Other leaves reduced and scale-like. Large leaf linear-lanceolate, acute, entire, to 20 cm long, 1 cm broad, glabrous, sheathing at the base, with expressed veins below which create a somewhat pleated appearance.

Calopogon tuberosus leaf

Inflorescence - Terminal raceme to 20 cm, with 3-10 flowers opening sequentially. Axis slightly zig-zag, glabrous. Each flower subtended by a subulate scale. Scales acute, to 5 mm long. Flowers sessile.

Flowers - Floral tube to 1 cm long, glabrous, green to purplish. Sepals and petals pink to purplish, glabrous. Sepals acute, to 2 cm long, 1 cm broad, the upper 2 somewhat oblique. Lower sepal oblong to narrowly elliptic. Upper lip of the corolla hinged, deflexed, with white, yellow and orange hairs at the apex, to 2 cm broad, broadest at the apex, 2 cm long, with two small basal lobes. Lobes acute, 2-3 mm long. Column arched and protruding from the rest of the flower, to 2 cm long, stout, winged near the apex and 7-8 mm broad, darker than the rest of the flower near the apex. Lateral petals to 2.2 cm long, oblong-elliptic.

Calopogon tuberosus flowerFlower.

Calopogon tuberosus lipLip with false anthers.

Fruits - Erect capsules, 18-21 mm long, elliptic in outline, strongly ribbed.

Flowering - June - July.

Habitat - Fens.

Origin - Native to U.S.

Lookalikes - Calopogon oklahomensis.

Other info. - This amazing orchid has been reported from only four counties in Missouri, all in the southern half of the state. It occurs predominantly in eastern coastal states but with at least scattered locations in all states in the eastern half of the U.S. The plant is fen obligate which greatly restricts its range in Missouri. Another species, C. oklahomensis D.H. Goldman, is found in mesic prairie habitats. This latter species is found in a handful of western counties in Missouri.

Both of these species are bee pollinated. The brilliantly colored, hairy upper lip of the corolla (which appears to a bee as stamens covered in pollen) is hinged and falls downward when a bee lands on it. This motion rubs the back of the bee against the column of the corolla, smearing pollen and a sticky adhesive substance onto the bee's back. Pollination occurs as this process is repeated among different flowers in the population.

Photographs taken near Stegal Mountain, Shannon County, MO., 6-21-03 and 6-13-05 (DETenaglia); also at St. Francois State Park, St. Francois County, MO, 6-19-2017 (SRTurner).


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