Penthorum

Scientific name

Penthorum L.

Common names

ditch stone crop, Virginia stone crop

Family

Penthoraceae

Native distribution

North America, Asia, and far eastern Russia

Species cultivated

Penthorum sedoides L. is sometimes commercially available as a pond and aquarium plant

Penthorum chinense Pursh

Adventive distribution

information not available

Weed status

not weedy

Habit

semi-aquatic herb

Brief description

Rhizomatous; stems ascending to erect, simple or ± branched, ± angled, glabrous basally, stipitate-glandular hairs above. Leaves alternate; sessile or shortly petiolate; leaf blade lanceolate to elliptic, glabrous or sparsely haired below; apex acuminate; base narrowly cuneate; margin serrate; venation pinnate. Inflorescence a terminal or axillary helicoid cyme, pedunculate; bracts ovate, small; pedicels glandular. Flowers small, yellow-green, white; sepals 5, triangular, margins entire or serrulate; petals typically absent or 5, lanceolate, slightly clawed; stamens 10 in 2 whorls; carpels 5, united below, styles short, forming beaks in fruit, stigmas small, capitate.

Natural habitat

margins of streams and rivers, in ditches, marshes, swamps and floodplains

Additional comments

A small genus of two species; of the two, Penthorum chinense has narrower leaves, more robust styles, and fewer-flowered inflorescences than P. sedoides.

Limnophila aromatica
(=L. aromaticoides) is frequently missidentified as Penthorum sedoides. Penthorum does not grow strongly submersed, (unlike L. aromatica) and is not as common in the hobby as L. aromatica.