Carmichaelia astonii
Common names
Aston’s dwarf broom
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Simplified description
Rare low-growing shrub with many erect greenish-brown leafless branches inhabiting limestone sites in Marlborough. The many branches are orange-tipped, leafless, erect, flattened, 4-8 mm wide, grooved, with hairy young growth. Flowers pea-like, pink, with darker centre. Fruit in a dry pod which has an upturned tip.
Flower colours
Violet/Purple, White
Detailed description
Dwarf and spreading shrub, up to 0.2 × 0.5 m. Branches stout, ascending and horizontal, 10-25 mm diameter. Cladodes linear, striate, compressed, erect to spreading, green to green-bronze, frequently hairy when young (hairs sometimes retrorse), 30-95 × 4-8 mm; apex subacute to obtuse, yellow to yellow-green; leaf nodes 2-4. Leaves simple, obovate to oblanceolate, fleshy, green or green-bronze, present on seedlings, absent on adult plants, 6-8 × 2.0-5.5 mm; upper and lower surfaces hairy; apex emarginate to retuse; base cuneate; petiole hairy, c. 2 mm long. Leaves on cladodes reduced to a scale, triangular, glabrous, < 0.5 mm long; apex acute. Stipules free, triangular, 0.9-1.0 × 0.7-0.8 mm; upper surface glabrous; lower surface hairy, becoming glabrous with age; apex acute; margin hairy. Inflorescence a raceme, 1-4 per node, each with l-4 flowers. Peduncle hairy, green, 7-8 mm long. Bracts triangular, glabrous, pale green, < 1 mm long; apex acute; margin hairy. Pedicel hairy, pale green, 2.5-8.0 mm long. Bracteoles at top of pedicel, green and occasionally flushed red, < 0.5 mm long; apex acute; margin hairy. Calyx campanulate, 4.5-5.5 × c.2.0 mm; inner surface glabrous, green; outer surface hairy, green and occasionally flushed red. Calyx lobes narrow-triangular, green and usually flushed red, 2.0-2.5 mm long; adaxial surface densely hairy; apex acute; two upper lobes usually appressed to base of standard; three lower lobes spreading away from keel. Standard obovate, patent, positioned in central area of keel, weakly keeled, margins recurved, c.12 × c.8 mm; central area of upper surface purple, margins white, sometimes purple-veined; lower surface white with a darkened central part; claw pale green, c.3 mm long; apex emarginate and occasionally mucronulate. Wings oblong, shorter than keel, c.9.0 × c. 2.5 mm; distal area of upper surface purple, proximal area pale green; lower surface white, purple-veined; auricle triangular, pale green, 1.0-1.25 mm long; claw pale green, 2.5-3.0 mm long; apex acute. Keel c.10 × c.3.5 mm; distal area of upper surface purple, proximal area white or pale green; auricle triangular, pale green, c.1 mm long; apex obtuse; claw pale green, 3.5-4.0 mm long. Stamens 9-11.5 mm long. Pistil exserted beyond stamens, c.12 mm long; ovary weakly falcate, glabrous; ovules 8-16. Pod oblong or oblanceolate, compressed, light grey or brown, valves often partially dehiscent, 14.0-23.0 × 4.0-7.5 mm; beak stout, pungent, 1-2 mm long. Seeds oblong-reniform, 4-8 per pod, olive green, green-yellow, or dull yellow, occasionally with black mottling, 2.5-3.5 × 1.5-3.0 mm.
Similar taxa
C. astonii is a allied to C. monroi Hook.f. and C. vexillata Heenan from which it is by its more robust growth habit; stouter cladodes; larger calyx, petals and pods; and by the long lower calyx lobes which spread away from the keel
Distribution
Endemic. New Zealand: South Island (Eastern Marlborough in a small area south of Ward, encompassing the Flaxbourne, Mead, Waima (Ure) River catchments, Weld Cone, Ward Beach and the Chalk Range).
Habitat
A limestone endemic, restricted to sparsely vegetated rendzina and related steepland soils of medium to high fertility.
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.
Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – these interim threat classification statuses has not been assessed by the NZTCS panel.
- 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 | Threatened – Nationally Vulnerable | Qualifiers: CD, DPS, DPT, RR, RF
Threats
A limestone endemic that is naturally restricted to a small geographical area. moderate-sized populations are known, and these appear to be secure though some are vulnerable to browse damage from goats, possums, and sheep. Of more concern is that seedlings are very rarely seen, and all populations are dominated by mature shrubs.
Detailed taxonomy
Family
Fabaceae
Synonyms
None
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
January - December
Fruiting
December – April
Life cycle and dispersal
Seeds are possibly dispersed by wind and granivory (Thorsen et al., 2009).
Propagation technique
Easily grown from fresh seed and hardwood cuttings. A very beautiful shrub that flourishes in a well drained, sunny situation. It does best on soil enriched in lime. Dislikes long periods of humidity.
Other information
Etymology
carmichaelia: After Carmichael, a botanist
astonii: After Aston
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.
CARAST
Chromosome number
2n = 32
Previous conservation statuses
2017 | Threatened – Nationally Vulnerable | Qualifiers: DP, RR, RF
2012 | Threatened – Nationally Vulnerable | Qualifiers: RF
2009 | Threatened – Nationally Vulnerable | Qualifiers: RF
2004 | Range Restricted
Referencing and citations
References and further reading
Heenan, P.B. 1995: A taxonomic revision of Carmichaelia (Fabaceae - Galegeae) in New Zealand (part I). New Zealand Journal of Botany 33: 455-475.
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 2009 Vol. 11 No. 4 pp. 285-309
Attribution
Description adapted from: Heenan (1996)