Crassula

Scientific name

Crassula L.

Common names

Australian swamp stonecrop, stonecrop, New Zealand pygmy weed

Family

Crassulaceae

Could be confused with

Microcarpaea

Native distribution

Australia, New Zealand

Species commonly cultivated

Crassula helmsii (Kirk) Cockayne (Australia, New Zealand)

Adventive distribution

Crassula helmsii is introduced into the United Kingdom.

Weed status

a serious environmental weed; displacing native plant species in the United Kingdom

Habit

emergent, attached stem plant

Brief description

Perennial. Creeping or ascending, forming a loose or sometimes tight mat-like stand, rooting at nodes. Leaves fleshy, opposite, decussate, sessile; leaf blade linear to elliptic, venation indistinct; margin entire. Inflorescence axillary, of solitary pedicellate flowers. Flowers bisexual, actinomorphic; sepals 3-5; petals white, 3-5, or sometimes absent or reduced. Dispersal by stem fragments or seed.

Natural habitat

shallow or clear water of streams, rivers, and lakes, particularly in temperate climates

Additional comments

Crassula is a very large genus of 300 species worldwide, with only four species being obligate aquatics. Only C. helmsii is cultivated for aquaria or ponds.