Plagianthus regius Hochr. var chathamicus (Cockayne)
Lowland Ribbonwood, Riverbank Ribbonwood, Ribbonwood,
ManatuPlagianthus regius Hochr.
Plagianthus regius Hochr. var chathamicus
(Cockayne)
Plagianthus divaricatus J.R. Forster & G.
Forster
Plagianthus is a genus with the family Malvaceae. The 2 species of Plagianthus are endemic to New Zealand (and the Chatham Islands). These are vernacularly known as ribbonwoods, a name which they share with species of the closely related (and fellow New Zealand endemic) genus Hoheria. Ribbonwoods are deciduous shrubs or trees, bearing small white or yellow-white flowers in late spring, followed by pendulous seeds.
It is distinguished from Hoheria by the presence of smaller flowers with linear stigmas and solitary carpels. (Hoheria has clusters of 5 or more carpels.)
The genus name is a reference to the petals of a Plagianthus flower not being all the same size.
The genus Plagianthus, as currently recognised, is endemic to New Zealand and the Chatham Islands, and consists of 2 species - the saltmarsh ribbonwood, Plagianthus divaricatus and the lowland ribbonwood, Plagianthus regius. It was introduced by J.R. and G. Forster for the former species.
In the past various authors have included species of Hoheria, and the Australian endemic genera Asterotrichion, Lawrencia and Gynatrix. Plagianthus humilis Blanco is Munronia humilis (Blanco) Harms, and belongs to the Meliaceae.
The genus belongs to the tribe Malveae, but its location within this tribe is not clear to me. It has in the past, possibly with allied genera, been raised to the rank of a tribe (Plagiantheae/Philippodendreae), subfamily (Philippodendroideae) or family (Plagianthaceae/Philippodendraceae).
The two species hybridise where they come into contact, e.g. on the banks of tidal rivers. Plagianthus cymosus T. Kirk is a name applied to at least one such hybrid.
IPNI also lists a Plagianthus linariifolia J. Buch., also from New Zealand. No further details have been found about this plant, and the name is assumed to be a synonym of either a Plagianthus or Hoheria species.
IPNI also lists a Plagianthus ribifolia Allan (syn. Gaya ribifolia Cockayne), also from New Zealand. No further details have been found about this plant, and the name is assumed to be a synonym of either a Plagianthus or Hoheria species. (The existence of a synonym in Gaya suggests this is a form or hybrid of Hoheria glabrata or Hoheria lyallii.)
Plagianthus regius Hochr.
Plagianthus regius Hochr. var chathamicus (Cockayne)
Lowland Ribbonwood, Riverbank Ribbonwood, Ribbonwood,
Manatu
Plagianthus regius is found over most of New Zealand, including Stewart Island and the Chatham Islands, but is absent from North Cape and Ninety Mile Beach in the far north. It grows in riparian habitats from sea level to 1500 ft, preferring moist soil.
It has distinct seedling, juvenile and adult forms.
The seedling form has an erect habit, and foliage similar to the adult form, but with truncate or cordate leaf bases.
The juvenile form (except in var chathamicus) is a dense bush of slender, interlaced, branches. The leaves are ovate, 5-15mm × 3-10mm, and serrated.
In its adult form it is New Zealand's largest deciduous tree, reaching 50 ft in height. The adult form, in its earlier stages, is a graceful, small to medium tree, reminiscent in habit of a Silver Birch. (Hence, presumably, the synonym Plagianthus betulinus.) When older it becomes broader and bulkier. (A specimen growing in an open location in Christchurch has a spread of 15m, and a trunk with a diameter of 1m.)
The foliage consists of ovate to ovate-lanceolate, toothed, leaves, from 1"-2½" long, and ¼"-2" wide, with a covering of stellate hairs on both surfaces. The yellowish-white flowers are small, but occur in large, tomentose, terminal panicles, in late spring. The calyx is campanulate. The petals are linear-oblong (narrower in male than in female flowers) and rounded at their tips. The staminal tube is long and slender, in the male flowers protuding beyond the petals, and bears many short-stalked anthers. The fruit is a small, ovoid, single-seeded, capsule, which on maturity splits down one side.
The population on the Chatham Islands is classified as var chathamicus. It is distinguished by a non-divaricating habit (i.e. non-interlaced branches) in the juvenile form.
Synonyms: Plagianthus betulinus A. Cunn., Plagianthus urticinus A. Cunn. and Philippodendron regium Poit. are synonyms of Plagianthus regius. Plagianthus chathamicus Cockayne is a synonym of Plagianthus regius var. chathamicus.
Plagianthus divaricatus J.R. Forster
& G. Forster
Saltmarsh Ribbonwood, Swamp Ribbonwood, Shore
Ribbonwood, Makaka, Runa
A spreading deciduous bushy shrub, growing to 8ft in height, and 12ft in width, to be found in saltmarsh and swamp habitats, over the whole of New Zealand, including those regions of the far north from which Plagianthus regius is absent. Like Plagianthus regius it has distinct juvenile and adult forms.
The juvenile form has 2-3.5cm long linear or spathulate leaves.
The adult form has 0.5-2 cm long linear, spathulate or narrow obovate, dark green, leaves. It bears very fragrant, small, yellowish-white tubular flowers, with 8-12 stamens, borne, solitarily or in small clusters, in leaf axils, in late spring. The glabrous calyx is hemispherical in form. The fruit is a small, downy, capsule containing 1 or 2 seeds, on maturity bursting irregularly.
Images
Synonyms: Napaea divaricata Alefeld is a synonym of Plagianthus divaricatus.
Oleander Scale, Aspidiotus nerii Bouché, and Greedy Scale, Hemiberlesia rapax (Comstock) Ferris, are recorded on Plagianthus divaricatus in New Zealand.
The rust fungus Puccinia plagianthi McAlpine (aka Puccinia hoheriae) infects all species of Hoheria and Plagianthus [7], and also the Australian species Gynatrix pulchella [9]. It causes leaf spotting and stem distortion, and can be diagnosed by the presence of irregular pale yellow, grey or brown blotches on both surfaces of green leaves or on distorted sections of the stem, by the presence of dark brown pustules (telia) (less than 2mm in diameter) on the lower surface of the leaves, either clustered in the blotches or scattered singly.on leaf surfaces, and by the presence of yellow spots (pycnia) on both surfaces of green leaves. Unlike many rust fungi Puccinia plagianthi does not (as far as is known) have an alternate host. It is not considered of economic importance, and control measures are not necessary. [8]
If you have found any errors on this page, or have any further information about the genus Plagianthus then please contact me at webmaster@meden.demon.co.uk.
© 2002, 2003, 2004, 2005 Stewart Robert Hinsley