1. Buddleja davidii Franch. (orange eye, summer lilac, common butterfly bush)

Map 2603

Plants shrubs with spreading or arching branches, 0.5–4.0 m tall, pubescent with minute, white, somewhat shiny, stellate hairs and small, globose, light yellow glands. Bark smooth or shallowly ridged or furrowed, gray to tan. Twigs rounded to slightly angled, purplish brown to green but often appearing grayish-tinged, with moderate to dense hairs and scattered glands. Leaves opposite, sessile or very short-petiolate. Stipules herbaceous, appearing as small, bluntly triangular to depressed-ovate flaps of tissue between the leaf bases. Leaf blades 2–15 cm long, narrowly elliptic to ovate-elliptic, tapered to a sharply pointed tip, narrowed or tapered at the base, the margins finely and sharply toothed, the upper surface sparsely hairy and sparsely glandular, appearing green, the undersurface with dense matted hairs and sparse to moderate glands, appearing silvery gray or white. Inflorescences terminal on the branches, narrow panicles to 20 cm long, sometimes appearing racemose, the flowers in clusters along short branches from the main axis. Flowers often subtended by 2 or 3 short linear bracts. Calyces 2.5–4.0 mm long, actinomorphic, shallowly 4-lobed, tubular to narrowly bell-shaped, sparsely to moderately hairy and glandular, the lobes triangular to narrowly triangular.. Corollas 9–12 mm long, actinomorphic, 4-lobed, trumpet-shaped, the tube moderately hairy internally and usually more than twice as long as the lobes, the lobes with rounded, irregular margins, reddish purple (rarely pink or white in cultivation) with the inner side of the tube and throat orange. Stamens 4, not exserted, the free portions of the filaments very short, the anthers appearing U-shaped, more or less 2-locular, yellow or orange. Staminodes absent. Ovary ovoid, 2-locular. Style about as long as the ovary, not exserted, the stigma 1, sometimes 2-lobed, club-shaped. Fruits 6–8 mm long, narrowly ellipsoid to cylindric-ovoid. Seeds 2–4 mm long, the body more or less ellipsoid, slightly flattened, tapered to a slender wing at each end, the surface smooth, brown. 2n=76. July–October.

Introduced, uncommon, widely scattered, usually in urban areas (native of Asia, introduced sporadically nearly throughout the New World, including the eastern and western U.S.). Roadsides, gardens, and open disturbed areas.

This species was first reported from the city of St. Louis by Mühlenbach (1979), based on a single plant growing immediately adjacent to a cultivated planting of the species. As the species continues to become more common in cultivation in the state, populations are sure to become established in other areas. It has become a problem invasive exotic in portions of the Pacific Northwest.