Agastache nepetoides (L.) Ktze.

Yellow Giant Hyssop

Agastache nepetoides plant

Family - Lamiaceae

Stems - From fibrous roots, to 3m tall, 4-angled, winged, glabrous or with sparse retrorse hairs on the angles, hollow, herbaceous, erect, branching (typically in the apical 1/2), single from the base.

Agastache nepetoides stemStem at a node.

Leaves - Opposite, petiolate, decussate. Petioles to +7cm long, with an adaxial groove, mostly glabrous but sparse pilose in the groove especially near the base of the blade. Blades ovate, to 11cm broad, 15cm long, crenate-serrate to serrate, rounded or subcordate at the base, acute, villous below, sparse pubescent above. Veins impressed adaxially, expressed abaxially.

Agastache nepetoides leavesPressed leaves.

Inflorescence - A terminal spike of closely clustered verticillasters. Spike to 20cm tall, 1.5cm in diameter, bracteate. Peduncle of spike densely pubescent. Each cyme of a verticillaster composed of +/-10 flowers. Flowers sessile. Bracts subtending the flowers equaling or shorter than the calyx.

Agastache nepetoides inflorescenceInflorescence.

Flowers - Corolla whitish, bilabiate, puberulent externally and internally, to 1cm long. Upper lip single-lobed. Lobe notched at apex, 1.6mm long, 2.1mm broad. Lower lip 3-lobed. Lateral lobes reduced and rounded, -1mm long. Central lobe expanded, 2mm long, +3mm broad, with lateral appendages, cupped. Stamens 4, exserted, didynamous, adnate in the apical 1/3 of the corolla tube. Filaments white, glabrous above, sparse pubescent basally, to 6mm long. Anthers bi-lobed, yellow, to .9mm broad. Style exserted, glabrous, white, 1.1cm long. Stigma 2-lobed. Ovary 4-lobed, subtended by a nectariferous ring, -.9mm broad. Lobes glandular apically, pubescent. Calyx tubular, subequally 5-lobed, puberulent, 5mm long in flower, accrescent. Lobes acute, entire, to 1.7mm long. Fruit of 4 nutlets. Nutlets pubescent.

Agastache nepetoides flowersFlowers.

Flowering - July - September.

Habitat - Open woods, thickets, moist soils, railroads.

Origin - Native to U.S.

Other info. - This species is common throughout Missouri. It is quite striking and should be cultivated more. The corollas are mostly off-white or very pale yellow. Most of the literature gives the corollas as yellowish to green. White seems to be the predominate color although the flowers do fade to a yellowish color when old.
Traditionally this species was used mixed with others and used to treat poison ivy.
Agastache is in the mint family but lacks a characteristic mint fragrance. nepetoides means "looks like Nepeta", which is catnip, and the two plants are fairly similar.

Photographs taken in the Ozark Scenic Riverways, Shannon County, MO., 7-29-03.