Spiranthes tuberosa Raf. - Ladies' Tresses

Spiranthes tuberosa plant

Family - Orchidaceae

Stems - Plant is without a stem until flowering. Flowering stem thin, glabrous, to 40cm tall but typically shorter, erect, herbaceous, simple, from a tuberous root. Root pubescent, typically single but often with the previous season's root persisting.

Spiranthes tuberosa root

Leaves - Basal rosette, few, ovate, to +3cm long, +1.5cm wide. Absent at flowering time (anthesis).
Plant rarely with small cauline leaves (bracts).

Inflorescence - Single spike to 9cm long, with some 25 flowers in a single spiral, flowers appearing secund on the axis.

Spiranthes tuberosa inflorescence

Flowers - Corolla white, glabrous, small, 2.5-4mm long, lip erose to undulate or crisped (curled).

Spiranthes tuberosa flowers

Flowering - August - October.

Habitat - Acid soils of upland pine, oak, or hickory forest (associated with granite, chert or sandstone substrata). Also in dry upland prairies and meadows.

Origin - Native to U.S.

Other info. - This is a fairly common species in Missouri. The plant can be identified by its tiny white flowers which are in a single spiral around the axis of the inflorescence. Each plant typically has one tuberous root but some plants have the tuberous root persisting from the previous season and thus have two roots.

Photographs taken at Fort Benning GA., 6-28-05.


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