Crassula helmsii (Kirk) Cockayne
Swamp Stonecrop, Australian Swamp Stonecrop, New Zealand Pigmyweed
Bulliarda recurva, Tillaea helmsii, Crassula recurva
Crassula helmsii is a small aquatic or semiterrestrial succulent with much-branched, creeping or floating stems with green, narrowly oval leaves. It can grow in several forms, establishing as a submersed plant and as an emergent or semi-terrestrial plant on damp ground. Leaves are up to 1 inch (2.5 cm) long and arranged in opposite pairs. Flowers are small, white or occasionally pink, with four petals, and appear solitary on stalks in the axils of the leaves in summer. They are always above water.
USDA hardiness zones 9a to 11b: from 20 °F (−6.7 °C) to 50 °F (+10 °C).
How to Grow and Care
Swamp Stonecrop is a stem plant grown both submersed or emersed and as a terrestrial plant. In fact, it must be controlled and watched in pond settings, so it does not escape into the garden.
It provides excellent cover for tadpoles, frogs, and small fish from birds and larger fish as a pond plant. However, it is prone to breaching the pond's surface, even if planted at 2 feet (60 cm) below the surface, which is not an issue as it allows the plant to flower, with its small white star-like flowers smaller than the stem width.
As an aquarium plant, the stems will thrive and should be treated as any other stem plant, pinched off at the top when they grow higher than required, and the tops replanted to prevent them from breaking the surface.
This is a highly vigorous plant, forgiving of many climate conditions. It grows throughout most of the year with minimal winter dieback.
This species is native to Australia and New Zealand.
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