Carmichaelia williamsii
Past favourite plant finalist
Common names
William’s Broom, Giant-flowered broom
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Simplified description
Rare robust coastal shrub with erect leafless wide flattened green branches. Branches 5-12mm wide, with wavy edge, lower branches drooping. Flowers large (to 25mm long), pea-like, white or yellow, sometimes striped. Pod a dry flattened pod containing 5-15 hard orange and black seeds.
Flower colours
Green, Yellow
Detailed description
Erect to suberect, spreading, usually leafless shrub up to 2-4 x 2-4 m. Branches 50-100 mm diam., stout, rather woody, ascending or spreading. Cladodes 130-380 x 5-12 mm, yellow-green, green to dark green, stout, linear, striate, compressed, glabrous, apex obtuse; leaf nodes 7-16. Leaves present on seedlings and reversion shoots or shaded cladodes of adult plants. Petiole 1-5 mm. Lamina fleshy, 1-3-foliolate, 6-23 x 5-15 mm, green often yellow toward proximal end, elliptic, obovate to broad-elliptic, apex retuse, base cuneate. Terminal leaflet larger than lateral leaflets. Leaves on cladodes reduced to scales, , 1 mm long, broad-triangular. Stipules 1.5 x 1 mm, free, broad-triangular, sometimes with a second pair of denticles. Inflorescence a 1-6-flowered raceme, usually in fascicles of 3-4 per node. Peduncle 1-6 mm long, hairy, green. Bracts 1-1.4 x 0.8-1.5 mm, narrow-triangular to broad-triangular, apex subacute to obtuse. Pedicel 4-8 mm long, hairy, pale green. Bracteoles 0.4-0.6 x 0.2 mm, narrow-triangular to linear, apex subacute. Calyx 8-9 x 4.7-5.5 mm, campanulate, green. Bud green becoming yellow-green at maturity. Standard 18-22 x 11-13.5 mm, ovate, patent, keeled, margins incurved, apex subacute to weakly retuse, greenish-yellow, yellow, to pale yellow with central portion and marginal veins maroon-red to purple. Wings 20-22 x 4-4.5 mm, oblong, falcate, shorter than keel, yellow to pale yellow. Keel 25-27 x 7-8 mm, apex narrow and acute, yellow, distal part of inner surface maroon-red or purple. Stamens 28-30 mm long; dorsal filaments fused for ¾ length, otherwise free for remainder of length. Pistil 32-33 mm long, exserted well beyond stamens. Pods 23-34 x 6-12 mm, oblong to oblanceolate, light to dark brown, valves dehiscent; beak 2-4 mm, stout, apex pungent. Seeds 5-15 per pod, 3-5 x 2-3 mm, reniform to oblong-reniform, dull red to orange-red usually mottled with black.
Similar taxa
This is the only yellow-flowered native New Zealand broom, and may be distinguished from the common introduced broom (Cytisus scoparius (L.) Link) by the non-leafy, light green, much wider, flattened branches, the larger, pale-yellow flowers with purple or red veins, and the late-winter flowering habit.
Distribution
Endemic. North Island only, where it known mainly from northern offshore islands (particularly the Poor Knights and Alderman Islands) to East Cape. On the mainland it is now known from only two small remnant populations near East Cape.
Habitat
A strictly coastal species of open forest, scrub, cliff faces and talus slopes.
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 | At Risk – Relict | Qualifiers: PD
Threats
Flowers, fruits and seed are palatable to rats. Some populations are at risk from coastal erosion. Plants tend to be short-lived, and are often inflicted with lemon tree borer (Oeomona hirta). Because the species is principally bird-pollinated, by New Zealand honeyeaters, the loss of these pollinators may affect reproductive effort. Though previously ranked as Nationally Endangered on the basis of the loss of mainland populations and the limited extent of island populations, it is now ranked as Relict on the basis that the loss of (most) mainland populations was historical and the island populations appear stable
Detailed taxonomy
Genus
Family
Synonyms
None
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
From July and October, though sporadic flowering may occur throughout the year.
Fruiting
Throughout the year.
Life cycle and dispersal
Seeds are possibly dispersed by wind and granivory (Thorsen et al., 2009).
Propagation technique
Easy from seed or hardwood cuttings. Seed germinates best if scarified and then soaked over night. An excellent winter to early spring flowering shrub for a coastal or lowland garden. Prefers full sun and free draining soil but will tolerate semi-shade. This species is usually short-lived (5-15 years), and it is wise to keep a few replacement plants going in pots just in case. Although it will tolerate snow and frost, it is better grown in warmer climates.
Other information
Plant of the Month
This plant has been featured as a Plant of the Month – see Trilepidea: NZPCN newsletter for June 2006 for the full story.
Etymology
carmichaelia: After Carmichael, a botanist
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.
CARWIL
Chromosome number
2n = 32
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 | At Risk – Relict | Qualifiers: PD
2012 | At Risk – Relict | Qualifiers: PD
2009 | At Risk – Relict | Qualifiers: PD
2004 | Threatened – Nationally Endangered
Regional conservation statuses
Auckland: 2025 | Regionally Threatened – Regionally Endangered | Qualifiers: CD, DPS, DPT, PF
The regional threat classification system leverages off the national assessments in the NZTCS, providing information relevant for the regional context. Auckland conservation status information is sourced from the “Conservation status of vascular plant species in Tāmaki Makaurau / Auckland” Simpkins E et al. (2025) report.
Referencing and citations
References and further reading
Heenan, P. B. 1996: A taxonomic revision of Carmichaelia (Fabaceae-Galegeae) in New Zealand. Part 2. New Zealand Journal of Botany 34: 157-177.
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
Fact Sheet prepared for NZPCN by P.J. de Lange 13 June 2006. Description modified from Heenan (1996).