Crassula: From the Latin crassus 'thick', meaning 'rather thick'
Helms crassula, New Zealand pygmyweed
2012 - Not Threatened
Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB
Previous Threat Status
2009 - Naturally Uncommon
2004 - Sparse
2012 - SO, Sp
Crassula helmsii (Kirk) Cockayne
Vascular - Native
Dicotyledonous Herbs other than Composites
Tillaea helmsii Kirk
?Endemic. In New Zealand known only from the West Coast of the South Island from Karamea south to just south of Haast. Naturalised in Britain where it is regarded as a serious weed.
Coastal to lowland, in shallow pools of fresh water or in damp usually shaded places, such as under rock overhangs, near waterfalls, and in shallow, slowly moving water. Occasionally it has been collected growing in exposed conditions on cobble beaches and gravel bars, but only where there is abundant fresh water flowing close to the surface.
Perennial, decumbent, herb forming diffuse to extensive mats. Stems green, pink or white, succulent, prostrate, rooting at nodes, ascending at tips, heavily branched. Leaves fused at base 2-7(-10) x 0.7-2 mm, 0.5-0.8 mm thick when fresh, narrowly lanceolate, oblong-lanceolate or elliptic-lanceolate, flattened above, strongly convex below, apex rounded or acute. Flowers solitary in leaf axils, fragrant, stellate, 4-merous, 3-4 mm diam.; pedicels 2-7 mm, not elongating at fruiting. Calyx lobes 1-2 x 0.5-0.6 mm, triangular-ovate, acute or subacute. Petals 1.2-2 x 0.8-1 mm, broadly elliptic-ovate, white with pink flush or pink, subacute > calyx. Scales 0.7 mm, oblanceolate. Follicles smooth. Seed 0.5 mm.
Distinguished from all other indigenous species of Crassula by the broadly-elliptic petals, whose length is 1.7x the width, and by the leaves which are 2-10 x 0.7-2 mm. In some respects it resembles a diminutive or elongated form of C. moschata G.Forst. - a strictly coastal, always terrestrial species, which has much larger flowers, and thicker leaves. C. helmsii can be very variable.
Flowers may be present throughout the year
Fruit may be present throughout the year
Easy from rooted pieces, and stem cuttings. Does best in damp soils or partially submerged, can become invasive. The white to pale pink flowers are sweetly scented
It is not clear if this species is actually threatened however, it does appear to be rather uncommon with a patchy distribution throughout its range in New Zealand.
2n = 14
Where To Buy
Can be purchased from Oratia Native Plant Nurseries (email@example.com).
Notes on taxonomy
Crassula helmsii which was first described from New Zealand has often been treated as indigenous to New Zealand and Australia. However the New Zealand plant is much smaller and more delicate than the Australian plant, and recent studies have shown that it can be distinguished from Australian plants by its diploid (2n = 14) rather than hexaploid (2n = 42) chromosome number, different nrDNA ITS sequence, and ecology. On this evidence Australian plants might better be referred to as C. recurva (Hook.f) Ostenf. However, further sampling from both countries is needed to confirm these observations. It would appear that it is the New Zealand plant which is naturalised in Britain.
This page last updated on 25 Oct 2013