Small, rarely medium, evergreen tree to 8(–11)m, not usually heteroblastic. Branchlets slender, grooved, with pale grey bark; with stellate hairs when young. Leaves of adult plant sometimes a little leathery; leaf blade broadly ovate to ovate-lanceolate or elliptic, (5–)7–14 × (3–)4–6 cm; apex acuminate (rarely acute, obtuse or rounded); base rounded, truncate or subcordate; margin deeply, coarsely, sometimes doubly, serrate-dentate; ± glabrous; petiole to ~2 cm. Juvenile plant usually similar in leaf form to adult. More rarely, juvenile plant with branchlets very slender, divaricate, ± entangled; leaf blade broadly-ovate to deltoid or suborbicular, (5–)10–30 mm long; margin serrate, ± deeply lobed (teeth sometimes crenate); petiole very slender, to 10 mm. Flowers ~25 mm across, both solitary and in (2–)5–10-flowered cymose clusters on same plant; pedicels ~10 mm, with stellate hairs; calyx campanulate, ~5 mm long, teeth triangular; petals ~10 mm long, white; stigmas capitate. Mature carpels 5(–6), compressed, 5–7 × 5–7 mm including broad wings. Flowering September (UK). (Allan 1961; New Zealand Plant Conservation Network 2021)
Distribution New Zealand N North Island, more widely naturalized
Habitat Coastal and montane forests dominated by Agathis australis or Metrosideros excelsa, 0–460 m.
USDA Hardiness Zone 9-10
RHS Hardiness Rating H3
Conservation status Not evaluated (NE)
This is the most tender of the Hoheria species in general cultivation. Widely grown in New Zealand, mature specimens are rarely seen in our area outside the mildest British and Irish gardens. Flowering later than other species, it can be very striking in the early autumn garden. All known variegated hoherias also belong here.
Among the evergreen species in cultivation, H. populnea is distinguished from both H. sexstylosa and H. angustifolia by its broader, more coarsely serrate leaves (though quite variable in shape) which often have purple-tinted veins. Its flowers are a little larger, appearing clustered towards the tips of the branches. It also tends to flower later than these species, usually in September in Britain, and is valued by New Zealand beekepers as a late source of nectar and pollen (Newstrom-Lloyd & McPherson 2017). Closely related to H. populnea is the more recently described H. equitum Heads (not cultivated in our area and probably very tender), restricted to the northerly Poor Knights Islands and Hen and Chickens Islands. It differs in its leathery leaves being untoothed, or almost so, often with recurved margins; its flowers tend to be smaller (Heads 2000).
This was the first Hoheria described scientifically, by Allan Cunningham from specimens collected around the Bay of Islands in 1825 and 1833; the collectors were Charles Fraser and later Richard Cunningham (Allan’s brother), successive Colonial Botanists of New South Wales, both of whose explorations included visits to New Zealand. The original description notes that it is ‘a large shrub, of agreeable aspect, and very ornamented growth’ (Cunningham 1839). It was certainly grown in the British Isles by the turn of the 20th century, when it flowered at Trinity College Botanic Garden, Dublin (Bean 1914). Early reports make it clear that this was not a fully hardy tree away from the mildest parts of the British Isles. Arnold-Forster (1948) noted that while in his own mild if exposed West Cornwall garden it belonged ‘in the first rank of flowering trees’, many examples elsewhere were killed or damaged in the severe weather of December 1937. Large examples in the British Isles include trees at Garnish Island, Co. Cork (16 m × 179 cm, 2004) and Trengwainton, Cornwall (16 m × 70 cm, 2014). It is no surprise that another Irish specimen at Fota Arboretum, Co. Cork (14 m × 153 cm, 2017) was planted in 1948, following the devastating winter of 1946–7 (Tree Register 2021). Fast growth, availability of nursery stock and often milder winters mean that even in less favoured areas this is becoming a species worth considering for short- to medium-term garden use. For example, a tree planted in 2005 in the Queen Mother’s garden at RBG Edinburgh has made an upright and floriferous specimen in full sun (pers. obs. 2021).
We have been unable to find records of H. populnea growing unprotected in other parts of Europe, or in our North American area. It would seem worth trying in coastal Brittany, Washington and Oregon, and perhaps in the American Southeast.
Several cultivars have been selected, mostly in New Zealand. The main sources of reference for these are the catalogues of North Island nurserymen Duncan & Davies from the 1920s onwards (available online at Royal New Zealand Institute of Horticulture 2020), and Hutchins (2006). In addition to those below, Duncan & Davies listed several distinct leaf forms around 1930, under spurious varietal names later treated as cultivars by Hutchins. The most interesting were perhaps var. linearis / ‘Linearis’ with distinctive narrow foliage and an open habit, and var. macrodonta / ‘Macrodonta’ with deeply toothed leaves giving a slightly holly-like appearance. These appear to be defunct.
A confusing range of forms – some named, some not – have a degree of purple coloration to the underside of the leaves. It is possible that they all derive ultimately from the same wild find, ‘Osbornei’. None seem to have a purple upper surface.
Other unnamed clones – perhaps seedlings from the cultivars – are in circulation under one or another of these names and synonyms. Hutchins (2006) found several different plants in British nurseries, none of them with blue stamens, but Ben Probert has found one example (labelled ‘Osbornei’) in a private Devon garden (pers. comm. 2021). Outside New Zealand, large examples of these rather tender plants are rarely seen. Bean (1981) mentions ‘Osbornei’ growing on Garnish Island, Co. Cork, Ireland, while a tree of 10 m × 154 cm was recorded in 2006 labelled “Hoheria purpurea” at Heligan, Cornwall (Tree Register 2021): these are both notably mild gardens.