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Julian Sutton (2021)
Sutton, J. (2021), 'Hoheria angustifolia' from the website Trees and Shrubs Online (treesandshrubsonline.
Medium evergreen, heteroblastic tree to 18 m, slender and fast growing. Bark grey; branchlets with fine, dense, stellate hairs. Leaves of adult plant clustered in fascicles, ± glabrous: leaf blade narrow, obovate to oblong or lanceolate, 2–5 × 0·5–1 cm (including teeth); apex obtuse to acute; margin coarsely spinulose dentate-serrate, teeth to 4 mm; petiole ~5 mm. Juvenile plant a small divaricate shrub with very slender, flexible, interlacing branchlets: leaves rather distant, often fascicled; leaf blade broadly obovate to suborbicular, (2–) 4–8 × 4–7 mm; base cuneate; margin dentate in upper part; petiole very slender, 1–2 mm. The different leaf forms may all occur on the same plant, the juvenile form often as reversion shoots on damaged mature trees. Flowers solitary or occasionally in 2–5-flowered cymose fascicles, on very slender stellate-hairy pedicels ~10 mm long. Calyx densely pubescent, campanulate, ~3 mm, (3–)5-fid; teeth broadly triangular. Petals ~7 mm long, white, obliquely narrow-oblong, notched. Stigma capitate. Anthers reniform. Carpels and styles 5. Mature carpels ~8 mm long, including very broad wing. (Allan 1961; New Zealand Plant Conservation Network 2021).
Distribution New Zealand South Island and S North Island, mainly towards the east
Habitat Alluvial forest, mostly lowland.
USDA Hardiness Zone 8-10
RHS Hardiness Rating H4
Conservation status Not evaluated (NE)
Hoheria angustifolia is one of the three evergreen species, small-leaved, with little white flowers in summer and a divaricate juvenile form. Garden specimens tend to be narrow and bolt-upright, with branchlets bearing mature foliage and flowers scattered among a tangle of juvenile shoots. The name is apparently much commoner than the plant itself in gardens, where hybridization is rife.
Distinguishing the evergreen species is not easy. H. sexstylosa has the most southerly range (it is the commonest evergreen hoheria on South Island), but overlaps with H. sexstylosa in places on both main islands. It is the only species with a full divaricate juvenile form (see below) although juvenile H. sexstylosa makes a small leaved, twiggy bush. In the adult form its leaves are still strikingly small, rarely more than 1 cm in breadth – this includes the usually long, sharp teeth – and frequently only 3 cm long. Most authors agree that the leaves are clustered towards the tips of the branchlets, a feature also seen in some of its presumed hybrids, and in clear contrast to H. sexstylosa and H. populnea, whose branchlets remain leafy much further back from the apex: how much of this is due to leaf longevity and how much to degree of internode extension requires further study. The relatively small flowers are most often solitary, while the majority are clustered in H. sexstylosa, even more so in H. populnea. As in H. populnea, the most frequent carpel number is 5 (H. sexstylosa more often has 6 or 7) but this is not diagnostic. However, even in the wild, hybridization (especially between H. angustifolia and H. sexstylosa) blurs these distinctions which are already heavily laced with ‘usually’ and ‘typically’ (New Zealand Plant Conservation Network 2021; Hutchins 2006). In gardens these problems are acute (see generic introduction) and it is not easy to find specimens which can confidently be labelled either ‘angustifolia’ or ‘sexstylosa’. Unfortunately most gardeners and nurseries do just this.
While several hoherias have distinct juvenile foliage, H. angustifolia is the only one with a truly divaricate juvenile form, making a dense tangle of widely branching, fine stems. Around 10% of the New Zealand woody flora is divaricate at least for part of the life cycle (Greenwood & Atkinson 1977). Two types of explanation have been advanced. One suggests that this habit is an adaptation to avoid browsing by moas (Greenwood & Atkinson 1977), a group of large, flightless birds which became extinct in the 15th century, within about 100 years of humans colonizing New Zealand (Worthy & Holdaway 2002). Others invoke climatic adaptations, either as a protection from frost, wind or dry air (McGlone & Webb 1981) or providing self-shading to protect against cold-induced photoinhibition (Howell, Kelly & Turnbull 2002). Uncertainty and disagreement remain.
Among the earliest species to be named scientifically, H. angustifolia was described by the French surgeon-botanist Étienne Raoul, who collected a specimen from the Banks Peninsula, South Island, during his productive three year stay in New Zealand (Raoul 1844). Plants fitting the description were apparently in Britain under this name by the 1930s. Arnold-Forster (1948) found that while it was slower growing than H. sexstylosa, it reached 9 m in his very exposed Cornish garden. Introductions of known wild provenance, which give a better chance of accurately named plants, are few. British nurseryman Graham Hutchins collected seed in 1985, again on the Banks Peninsula, and distributed many seedlings from his County Park Nursery (Hutchins 2006). As is usual in Hoheria, hybrids often do service for the species in British gardens; most have some features in common with H. angustifolia, but not all; some have much larger leaves, for example (pers. obs. 2021). The hybrid cultivar ‘Borde Hill’ has sometimes been placed here (Bean 1981).
Even in the wild, hybrids are well known if not always well characterized. Diverse hybrids with H. lyallii occur on South Island; H. × allanii (Cockayne) Heenan covers all such crosses (Heenan et al. 2005; Wagstaff, Molloy & Tate 2010). Hybrids with H. sexstylosa are known from both main islands (Wagstaff, Molloy & Tate 2010; New Zealand Plant Conservation Network 2021).
Most records of significant trees in gardens outside New Zealand are from the south of England (the usual caveats around identification strongly apply). Two examples at Tresco Abbey Gardens (10 m × 142 cm and 11 m × 127 cm, 2016) show what can be acheived in time without severe winter cold (Tree Register 2021). In Belgium it is recorded at Arboretum Wespelaar and Meise Botanic Garden (Plantcol 2021), while in North America it is recorded, along with several other species and hybrids, in Seattle’s Washington Park (University of Washington Botanic Gardens 2019).