Aureolaria grandiflora (Benth.) Pennell

Big-Flowered Gerardia

Aureolaria grandiflora plant

Family - Scrophulariaceae

Stems - To 1.3m tall, multiple from base, herbaceous, branching, erect. 4-angled, densely short pubescent.

Aureolaria grandiflora stemStem.

Leaves - Opposite, lowest leaves pinnately lobed (pinnatifid), upper leaves becoming simple, dense pubescent above with stellate pubescence on midrib and veins, dense pubescent below, serrate to crenate or entire, lowest leaves to +15cm long, +8cm broad.

Aureolaria grandiflora leafMiddle leaf.

Inflorescence - Appearing as single flowers from upper leaf axils but actually loose racemes terminating stems. Flowers opposite. Each flower subtended by foliaceous bracts. Pedicels to +8mm long, tomentose, typically upcurved.

Aureolaria grandiflora stemRaceme.

Flowers - Corolla yellow, campanulate, zygomorphic, 5-lobed. Corolla tube to +2.5cm long, glabrous externally, pubescent internally. Corolla lobes spreading, rounded, 1.2cm long, 1.5cm broad, unequal to subequal. Stamens 4, didynamous, adnate near base of corolla tube. Filaments to -2cm long, villous at base and sparse villous near apex, brownish-purple. Anthers to 5mm long, villous, purplish-brown. Style 1.8cm long, yellow, glabrous. Ovary superior, yellow, ovoid, 2-locular, subtended by green nectar ring. Placentation axile. Ovules (seeds) many. Calyx tube to 1cm long, tomentose, campanulate, 5-lobed. Lobes unequal, to 9mm long, dense pubescent.

Aureolaria grandiflora calyxCalyx and corolla tube.

Aureolaria grandiflora flowerCorolla.

Fruits - Capsules to 2cm long, glabrous.

Aureolaria grandiflora fruitsFruits.

Flowering - July - September.

Habitat - Rocky open woods, slopes, ridges, bluffs, glade margins.

Origin - Native to U.S.

Other info. - This species can be found throughout most of Missouri but is apparently absent from the northwest and southeast corners of the state. The big bright yellow flowers are hard to miss in the field.
The plant is semiparasitic on the roots of oak trees but apparently does well if grown in a garden setting.

Photographs taken at Lichen Glade, St. Clair County, MO., 7-27-00 (DETenaglia); also at Little Lost Creek Conservation Area, Warren County, MO, 8-21-2016 and 9-6-2016 (SRTurner).