Stachys tenuifolia Willd. - Smooth Hedge Nettle

Stachys tenuifolia plant

Family - Lamiaceae

Stems - To +1.2m tall, 4-angled, herbaceous, hollow, branching above, erect, retrorse strigose on angles, glabrous between angles, from rhizomes.

Stachys tenuifolia rhizomeRhizome.

Stachys tenuifolia stem

Leaves - Opposite, decussate, petiolate. Petiole to -3cm long, winged, glabrous or with sparse pubescence at base. wing to -1mm broad. Blade lanceolate to lance-oblong, to +13cm long, 4cm broad, crenate-serrate, acuminate, glabrous but with a scabrous midrib.

Stachys tenuifolia plant

Inflorescence - Terminal spikiform arrangement of verticillasters. Verticillasters with +/-6 flowers, subtended by small foliaceous bracts. Flowers sessile to subsessile.

Flowers - Corolla bilabiate, pinkish with purple streaks and spots internally. Corolla tube to 7mm long, glabrous, white near base. Upper lip of corolla 5mm long, 4mm broad, glandular pubescent externally, glabrous internally, obtuse at apex. Lower corolla lip 3-lobed, glabrous internally and externally. Lateral lobes -2mm long. Central lobe 3mm long, 3.5mm broad. Stamens 4, didynamous, adnate at apex of corolla tube, exserted from upper lip of corolla. Filaments to 3mm long, glandular pubescent, white. Anthers brownish-purple, 1.2mm long. Style white to purple at apex, 1.1cm long, glabrous. Stigma 2-lobed. Ovary of 4 nutlets. Nutlets greenish-white, 3-ribbed, becoming black and 1.7mm long in fruit.
Calyx tube to 2.5mm long, sparse pubescent, 5-lobed. Lobes equal, attenuate, 2.5mm long, typically glabrous.

Stachys tenuifolia calyxCalices, corollas removed.

Stachys tenuifolia flowersFlowers close-up.

Flowering - June - September.

Habitat - Moist and low woodland, ravines, streambanks, pond margins, swamps, wet meadows.

Origin - Native to U.S.

Other info. - Stachys tenuifolia and the similar S. palustris L. would make excellent garden subjects for anyone with a shade garden and moist to wet ground. The flowers are good for attracting flying insects and are striking to look at.
Steyermark breaks S. tenuifolia into two varieties. Variety tenuifolia, described above, has petioles to 3cm long and is glabrous on the leaves, calyx, and calyx lobes. This variety is found throughout most of the state. Variety hispida (Pursh) Fern. has petioles to 8mm long and is hispid to appressed pubescent on the leaves, calyx, and calyx lobes. This variety is mostly found in the upper half of the state, north of the Missouri river.

Photographs taken in the Irish Wilderness, Mark Twain National Forest, Oregon County, MO., 7-15-00.


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