Crassula helmsii
Common names
Helms’s crassula, New Zealand pygmyweed
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Flower colours
White
Detailed description
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. The white to pale pink flowers are sweetly scented.
Similar taxa
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.
Distribution
?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.
Habitat
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.
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | Not Threatened | Qualifiers: SO, Sp
Threats
This species appears to be rather uncommon with a patchy distribution throughout its range in New Zealand.
Detailed taxonomy
Genus
Family
Synonyms
Tillaea helmsii Kirk
Taxonomic notes
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.
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
Flowers may be present throughout the year
Fruiting
Fruit may be present throughout the year
Life cycle and dispersal
Minute follicles are dispersed by wind and water and possiblty also by attachment (Thorsen et al., 2009).
Propagation technique
Easy from rooted pieces, and stem cuttings. Does best in damp soils or partially submerged. Can become invasive in some modified situations.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FACW: Facultative Wetland
Usually is a hydrophyte but occasionally found in uplands (non-wetlands).
Other information
Etymology
crassula: From the Latin crassus ‘thick’, meaning ‘rather thick’
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
CRAHEL
Chromosome number
2n = 14
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | Not Threatened | Qualifiers: SO, Sp
2012 | Not Threatened | Qualifiers: SO, Sp
2009 | At Risk – Naturally Uncommon
2004 | Sparse
Referencing and citations
References and further reading
Webb CJ, Sykes WR, Garnock-Jones PJ 1988. Flora of New Zealand. Vol. IV. Botany Division, DSIR, Christchurch.
Thorsen, M. J.; Dickinson, K. J. M.; Seddon, P. J. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285-309.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange 1 February 2008. Description based on Webb et al. (1988)
Some of this factsheet information is derived from Flora of New Zealand Online and is used under a Creative Commons Attribution 3.0 New Zealand licence.