Buddleja davidii Franch.
Family - Scrophulariaceae
Stem - Arching and spreading, to 4 m, pubescent with minute stellate hairs, also with small, light yellow glands.
Leaves - Opposite, sessile or short petiolate. Blades elliptic or lanceolate, sharply pointed, upper surfaces sparsely hairy, lower surfaces tomentose and moderately glandular, appearing whitish. Margins finely toothed. Stipules herbaceous, appearing as small flaps of tissue between leaf bases.
Inflorescence - Terminal on branches, dense panicles to 20 cm long.
Flowers - Calyx 2.5-4.0 mm long, actinomorphic, hairy, glandular, shallowly 4-lobed, lobes triangular. Corollas 9-12 mm long, actinomorphic, trumpet-shaped, internally hairy, lobes with irregular margins, bluish purple with an orange throat. Stamens 4, inserted. Ovary 2-locular. Style inserted, with single club-shaped stigma.
Calyces and corolla tubes.
Fruits - 6-8 mm long, narrowly ellipsoid to cylindricovoid. Seeds 2-4 mm long, ellipsoid, slightly flattened, tapered to a slender wing at each end, the surface smooth, brown.
Flowering - July - October.
Habitat - Roadsides, homesteads.
Origin - Native to Asia.
Other info. - This species is usually found only at former homesites or persisting from deliberate plantings, rarely escaping cultivation in Missouri. The flowers are sources of nectar and attract butterflies. The plant is considered a noxious pest in areas of the Pacific Northwest.
Photographs taken near Washington, Franklin County, MO, 8-27-2017 (SRTurner).