Acrothamnus colensoi

A. colensoi was described in 1864 by Joseph Hooker as Cyathodes colensoi, and named after William Colenso, the New Zealand missionary, botanist and politician.{{Cite book |last=Eagle |first=Audrey |url=https://www.wikidata.org/wiki/Q63848049 |title=Eagle's complete trees and shrubs of New Zealand volume two |publisher=Te Papa Press |year=2008 |isbn=9780909010089 |location=Wellington |pages=550 |language=English}}{{cite web |last1=de Lange |first1=P. J. |title=Acrothamnus colensoi |url=http://www.nzpcn.org.nz/flora_details.aspx?ID=927 |access-date=20 May 2016 |website=www.nzpcn.org.nz |publisher=New Zealand Plant Conservation Network}} It remained in Cyathodes for many years before being assigned to the genus Leucopogon, and then moved to Acrothamnus in 2005.{{cite journal|last1=Quinn|first1=Christopher J.|last2=Brown|first2=Elizabeth A.|last3=Heslewood|first3=Margaret M.|last4=Crayn|first4=Darren M.|title=Generic concepts in Styphelieae (Ericaceae): the Cyathodes group|journal=Australian Systematic Botany|date=2005|volume=18|issue=5|pages=439–454|doi=10.1071/SB05005|url=http://www.publish.csiro.au/paper/SB05005.htm|access-date=20 May 2016}} It had been treated as A. suaveolens (a species now considered endemic to Borneo) but was separated by an examination of DNA and chromosome number.

The species is a low-growing or prostrate shrub that is sprawling and branched, usually 40 cm tall by 60 cm across but sometimes forming patches 2 m across.{{Cite book |last=Metcalf |first=Laurie |title=A Photographic Guide to Alpine Plants of New Zealand |publisher=New Holland |year=2006 |isbn=978-1-86966-128-1 |location=Auckland |pages=60}} The leaves are sessile or subsessile and are pinkish green to red-brown. The branches are ascending to erect, weakly ribbed and a grey-brown colour.{{cite web |title=Acrothamnus colensoi (Hook.f.) Quinn |url=http://www.nzflora.info/factsheet/taxon/Acrothamnus_colensoi.html |access-date=20 May 2016 |website=Flora of New Zealand |publisher=Landcare Research}} Its berries are 4–5 mm in diameter, globose, fleshy, and glossy; colours range between white, pink, red, and crimson to almost black. Their thin flesh conceals 5 hard seeds.

Its leaves are 5–10 by 1–4 mm, alternate and spreading with greenish veins and white interveinal grooves; they have 3–5 prominent parallel veins and can have a white stripe on the underside.{{Cite book |last=Poole |first=Lindsay |title=Trees and Shrubs of New Zealand |last2=Adams |first2=Nancy |publisher=DSIR Publishing |year=1990 |isbn=0-477-02603-6 |location=Wellington |pages=154}} Leaf margins are distinctively finely hairy when young, but mostly glabrous, and rolled downwards and inwards.{{cite web |last1=Flora Committee |title=Acrothamnus colensoi (Hook.f.) Quinn |url=https://www.nzflora.info/factsheet/taxon/Acrothamnus-colensoi.html |publisher=NZflora |access-date=2023-05-17}} The leaves are distinctively lozenge shaped: oblong, then narrowing to a fine point.

Its honey-scented flowers are white to yellowish, and produced in clusters of 2–5 at the tips of the branches. They are subtended by two keeled bracteoles and a bract which is up to 2.5 mm long and pinkish green to red in colour. This is glaucescent, broadly ovulate, obtuse and ciliolate. The bracteoles are very similar but smaller and distinctly keeled. The sepals are up to 4 mm long and imbricate with stomata only on the adaxial surface. The flowers are between 6–8 mm long, with a 4–5 mm long corolla tube, hairy in its upper part. Flowers have both male and female parts, but often function as only male or female; those that act as female can bear fruit.

A. colensoi's chromosome number is 2n = 146, distinctive and unlike anything seen in other members of the ericoid Styphelieae in New Zealand.Murray, B.G.; de Lange, P.J. (2013:). "Contributions to a chromosome atlas of the New Zealand flora – 40. Miscellaneous counts for 36 families." New Zealand Journal of Botany 51: 31–60.

File:Acrothamnus colensoi kz3 (cropped).jpg|Flowers

File:Acrothamnus colensoi 346631025 (cropped).jpg|Fruit

File:Acrothamnus colensoi kz1 (cropped).jpg|Leaves

Acrothamnus colensoi (Hook.f.) Quinn (AM AK6840).jpg|Type specimen from the Auckland War Memorial Museum herbarium

File:Acrothamnus MRD 03.jpg, Canterbury]]

A. colensoi is endemic to New Zealand. It is found in both main islands, from the central North Island to Otago. In the South Island it can be found in drier eastern mountains of Marlborough and Canterbury, locally in Otago and rarely in northern Southland. Its habitat is generally montane to low-alpine (600–1600 m), extending to lower altitudes in the southern part of its range. It prefers well-drained sites in shrubland, tussock grassland, and rocky outcrops.

This species flowers from September to February and begins fruiting in November, ending in June. The berries are fleshy and eaten by birds, reptiles and invertebrates (although hardly palatable to humans); the leaves and flowers are very rarely eaten.

A. colensoi is not a threatened species, but it is very difficult to propagate and should not be removed from the wild.

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• [https://inaturalist.nz/observations?taxon_id=399383 iNaturalist observations] of Acrothamnus colensoi

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Category:Plants described in 1864

Category:Endemic flora of New Zealand

Category:Epacridoideae