Houstonia caerulea L.
Family: Rubiaceae
Houstonia caerulea image
Morton Arboretum  
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

From Flora of Indiana (1940) by Charles C. Deam
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.


Indiana Coefficient of Conservatism: C = 9

Wetland Indicator Status: FAC