Annual or perennial herb with a very slender rhizome 5 - 20 cm tall
Leaves: opposite. Lower leaves stalked, 5 mm - 1.5 cm long, reverse lance-shaped to spatula-shaped with a narrowed base. Upper leaves nearly stalkless, reduced in size, and much narrower than the lower leaves.
Flowers: light blue to lilac, yellow in center, trumpet-shaped, with four spreading lobes (limbs). The tube is 0.5 - 1 cm long and the limbs are 2.5 - 4 mm wide. Stamens included. Style one, stigmas two.
Fruit: a small, dehiscent capsule, 3 - 4 mm wide, broader than long, flattened, paired. Seeds spherical, pitted.
Stems: shortly creeping, eventually forming clumps, slender, sparingly branched below.
Flower stalks: terminal and from the upper axils, one-flowered, upright, slender, 2 - 7 cm long.
Similar species: The light blue, yellow-eyed flowers distinguish this species from all other Houstonia in the Chicago Region.
Flowering: mid-April to late August
Habitat and ecology: Locally frequent in flat sandy prairies and occasionally found in sterile areas of woodlands.
Occurence in the Chicago region: native
Etymology: Houstonia is named after Dr. William Houston (1695-1733), a Scottish-born surgeon and botanist who collected plants in Mexico and the West Indies. Caerulea means "dark blue."
Author: The Morton Arboretum
Mostly in the northwestern and southeastern parts of the state. This species prefers a slightly acid soil and is usually found in black sandy soil in woodland or pastures in the northwestern part of the state, and in open woodland and fallow fields in the southeastern part of the state. Where it is found it is usually common, sometimes covering acres.
Delicate perennial with very slender, fragile rhizomes, eventually forming clumps to 1 dm wide, but apparently blooming the first year and thus potentially annual; lower lvs oblanceolate to spatulate, 5-12 mm, narrowed to a petiole often as long; upper lvs subsessile, oblong-spatulate to linear; peduncles erect, slender, terminal and from the upper axils, 2-7 cm, 1-fld; fls heterostylic; sep narrowly oblong, 1-2 mm, acute; cor typically rather light blue-lavender with a pale yellow eye, salverform, the tube 5-10 mm, glabrous within, the limb 10-14 mm wide; stamens included; fr didymous-flattened, 3-4 mm wide, much broader than long; seeds globular, with a deep round cavity occupying the inner face; 2n=16, 32, 48. Moist soil and meadows; N.S. and Que. to Wis., s. to Ga. and Ark. Apr.-June. (Houstonia c.; Houstonia faxonorum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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