";s:4:"text";s:6581:" Petals 1.2-2 x 0.8-1 mm, broadly elliptic-ovate, white with pink flush or pink, subacute > calyx. (Year at time of access): Crassula helmsii Fact Sheet (content continuously updated). Michelle Nault, Wisconsin Department of Natural Resources, 2801 Progress Rd, Madison, WI 53716-3339, USAOne or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.Please consider upgrading your browser to the latest version or installing a new browser.More information about modern web browsers can be found at
Flora of New Zealand. Action: Crassula helmsii: Biological control using fungal-based herbicides Key messages Read our guidance on Key messages before continuing. The fruits contain 2-5 smooth, elliptical seeds 0.5 mm long (OEPP/Infestations of aquatic invasive species are often first reported at boat launches and public access points and these areas should be monitored frequently in order to eradicate or control new invasions at an early stage. 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. Angiosperm Phylogeny Website. St Louis, Missouri, USA: University of Missouri and Missouri Botanical Garden. When several references are cited, they may give conflicting information on the status.
Follicles smooth. The species is one of the biggest threats to ponds in the UK, completely blanketing the surface once established and dominating any available space. Crassula helmsii (Crassulaceae). Scales 0.7 mm, oblanceolate. 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. Wallingford, UK: CABICABI, Undated a. CABI Compendium: Status as determined by CABI editor. Calyx lobes 1-2 x 0.5-0.6 mm, triangular-ovate, acute or subacute.
; pedicels 2-7 mm, not elongating at fruiting. Crassula helmsii, also known as the New Zealand Pigmyweed or Australian Swamp Stonecrop is an aggressively invasive plant,having been present in the UK since 1911 (CAPM: CEH, 2004). Botany Division, DSIR, Christchurch.Thorsen, M. J.; Dickinson, K. J. M.; Seddon, P. J. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Genetic studies of New Zealand plants show a difference in chromosome number, with Australian plants being diploid (2n=14), and the smaller, more delicate plants from New Zealand being hexaploid (2n=42) (Hydrochory, the dispersal of disseminules by water currents, seems to be the main dispersal mode of vegetative fragments within a watershed. Flowers have four petals, are white or occasionally pink, 3-3.5 mm in diameter, and are borne singly on stalks in the axils of the leaves. It would appear that it is the New Zealand plant which is naturalised in Britain.Fact sheet prepared for NZPCN by P.J. The succulent linear to narrowly oval leaves are opposite and sessile, 4-24 mm long and 0.7-1.6 mm wide. Perspectives in Plant Ecology, Evolution and Systematics 11: 285-309Please cite as: de Lange, P.J.
- a strictly coastal, always terrestrial species, which has much larger flowers, and thicker leaves. However, further sampling from both countries is needed to confirm these observations. Users should inspect all recreational equipment before leaving any water body, and any visible plants, animals, or sediment should be removed. In some respects it resembles a diminutive or elongated form of C. moschata G.Forst.
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: Crassula helmsii (Crassulaceae), Denmark: North European and Baltic Network on Invasive Alien Species (NOBANIS).
Originally found in Australia and New Zealand, it has been introduced around the world. Crassula helmsii was able to re-grow to the same greater extent following treatment which is highly undesirable in ponds which contain species with high conservation value. 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. The white to pale pink flowers are sweetly scentedIt 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.Crassula helmsii which was first described from New Zealand has often been treated as indigenous to New Zealand and Australia. Flowers solitary in leaf axils, fragrant, stellate, 4-merous, 3-4 mm diam.