Olearia colensoi aka Leatherwood

Leatherwood (Olearia colensoi, tūpare) is a tree daisy and produces branched racemes up to 20 cm long carrying many small daisy-like capitula 2–3 cm across. Florets are all tubular (no ray florets in wild forms; horticultural accounts also mention ray florets) and range from mauve-purple to dark red or cream depending on the plant. Flowering runs from November to January in its native Southern Hemisphere, with fruiting December to February. Flowering is mast-like — heavy displays follow warm summers.

Leatherwood is insect-pollinated. Like most New Zealand Asteraceae, its many small tubular florets attract native and introduced bees and flies. Synchronised mast flowering during warm summers is thought to boost pollination success through efficiencies of scale. There is no evidence of wind or bird pollination.

Leatherwood flowers are not noted for strong fragrance in horticultural or botanical records. Some Olearia species have a faintly musky or honey-like daisy scent when in full bloom, but tūpare is valued for its foliage and structural form rather than perfume. The crushed leaves have a faint resinous smell from the dense white tomentum.

No. Leatherwood is not a food plant. Its leaves are thick, leathery and coated in dense white hairs, and there are no records of Māori or later food use for any part of the plant. There is no documented toxicity either, but it should not be eaten.

Historical Māori use of tūpare for medicinal purposes is referenced in ethnobotanical sources, but specific applications are poorly documented. It is not a prominent rongoā (Māori medicine) plant compared with its cousin kūmarahou (Pomaderris kumeraho), with which its Māori name is sometimes confused. It has no modern herbal or pharmaceutical use.

Leatherwood is the dominant shrub of New Zealand's 'leatherwood scrub' — the largest continuous area of subalpine Asteraceae-dominated scrub in the country, particularly extensive in the Ruahine Range. Ecologically it stabilises wet, windswept subalpine slopes and forms impenetrable thickets that shelter native fauna. Māori on the Titi (Muttonbird) Islands used tūpare — the most common shrub there — as the principal timber for building traditional round whare, taking advantage of stems naturally curved by coastal wind. In modern horticulture it is planted for wind-tolerant hedging, riparian restoration, and native forest revegetation, and its flowers attract bees and birds.

Olearia colensoi grows in the wet subalpine zones of New Zealand, where soils are typically acidic, peaty loams derived from volcanic or sedimentary parent material. In cultivation, aim for a free-draining but consistently moist, humus-rich mix with an acidic pH (around 4.5–5.5). Avoid chalky or alkaline soils and waterlogged clay — leatherwood likes moisture moving through the root zone, not stagnating around it.

Leatherwood is challenging in cultivation and rarely grown outside specialist collections. It is adapted to New Zealand's cool, wet, windy subalpine conditions (or cool coastal areas in the far south), which are difficult to replicate in typical gardens. It has succeeded in mild, oceanic climates such as Tresco Abbey (Isles of Scilly) and Inverewe (Scotland), but at Kew Gardens it requires cool greenhouse protection.

Olearia colensoi (now often treated as Macrolearia colensoi) is endemic to New Zealand. It grows in the eastern and southern axial ranges of the North Island, around Marlborough Sounds (Mt Stokes), in the western South Island, on Rakiura / Stewart Island, and on some adjacent offshore islands. It occupies subalpine scrub where it can form impenetrable thickets, and descends to sea level in the far south.

Leatherwood is a wild subalpine shrub and has no documented fertilizer regime. Like most Olearia, it prefers a peaty, free-draining soil and benefits more from organic mulch than from heavy feeding. A light application of a balanced slow-release fertilizer in spring is usually more than sufficient; avoid rich or soggy soils.

In spring, mulch lightly and carry out any hard renovation pruning before new growth hardens. Summer is the season to take semi-ripe cuttings and to keep the root zone cool and evenly moist. Flowering typically occurs in November–January (Southern Hemisphere summer); prune after flowering to shape. In winter, protect from hard frosts in marginal climates — a sheltered, cool but frost-free position is ideal for plants outside their native range.

There are no widely cultivated named cultivars of leatherwood. The former variety Olearia colensoi var. argentea is no longer recognized and is now regarded as part of natural variation within the species. Plants from high-altitude populations (notably Mt Hikurangi, up to ~1,500 m / 5,000 ft) are reportedly hardier than the lowland Stewart Island forms that reached European gardens.

Outdoors is the only sensible place to grow it — leatherwood is a tough subalpine shrub, not a houseplant. It is best suited to mild, oceanic, high-rainfall climates (roughly USDA zones 8–10). Choose a site with free-draining peaty soil, cool roots, and protection from hot, dry summer winds. It tolerates salt spray, coastal wind, and partial shade well, but dislikes prolonged hard frost and dry continental conditions.

Pruning is optional but tolerated. Like other Olearia, leatherwood responds well to a light trim just after flowering to maintain a dense, shapely bush. Overgrown or leggy plants can be cut back harder in early spring before new growth begins. Avoid deep cultivation around the base — the roots are shallow and easily damaged.

Leatherwood is not a typical container plant, but young specimens or those grown under glass in cold climates can be kept in large pots. Use a peaty, free-draining mix, pot on in early spring before active growth, and handle the shallow root system gently. Long-term it prefers to be planted out into the ground where its roots can run cool and moist.

Leatherwood is usually propagated from semi-ripe (half-hardened) cuttings taken in summer or early autumn, following the general recipe for the genus Olearia. Cuttings root in a gritty, peat-based mix under humidity. Propagation from seed is also possible, though seed can be slow and erratic, and wild-collected seed is preferred by specialist nurseries.

Yellowing foliage on Olearia colensoi most often points to root stress: waterlogged soil, compacted ground, or conversely extreme drought. Because it naturally grows on peaty, free-draining but constantly moist subalpine soils, it dislikes both soggy and bone-dry conditions. Check drainage, mulch to keep roots cool, and make sure the plant is not being scorched by hot afternoon sun in a dry climate.

Brown, crispy leaf edges usually indicate wind scorch, frost damage, or drought — all of which this species shows readily when grown outside its native cool, humid range. Hard frosts can kill back younger shoots in marginal climates. Site plants with shelter from dry winds and hard frost pockets, and keep the root zone evenly moist through summer.

Drooping or limp leatherwood usually signals a root-zone problem. A bone-dry, peaty pot that has dried out shrinks away from the sides and stops absorbing water — soak it deeply to rewet. Conversely, waterlogged soil smothers the shallow roots and causes sudden collapse; in that case, reduce watering, improve drainage, and trim away any mushy roots. Transplant shock and severe cold can also cause temporary droop.

Leatherwood is evergreen and holds its thick leathery leaves for multiple seasons, so significant leaf drop is a warning sign. The most common triggers are root rot from waterlogged soil, sudden transplant shock, or damage from a severe cold snap. Check the roots for firmness and the soil for drainage, and avoid disturbing the shallow root system.

Slow growth is normal for Olearia colensoi. In the wild it is a tough, slow-growing subalpine shrub that puts its energy into dense, wind-resistant foliage rather than rapid height. Expect modest annual growth, especially in cooler climates. Providing shelter, steady moisture, and a peaty mulched soil will give the best growth you can reasonably expect.

There are no pests or diseases specifically documented as serious problems for leatherwood in cultivation — it is rarely grown and generally robust. The main risks are root rot in poorly drained soils and generic Olearia issues such as occasional scale insects or leaf-spot fungi in humid, still air. Good drainage, airflow, and a healthy site are the best defenses.

Leatherwood is native to New Zealand's cool, moist subalpine zones (and down to sea level in the far south), so it is adapted to a cool temperate oceanic climate with mild summers and frosty — but rarely severe — winters. It is roughly USDA zones 8–10 and RHS H4 in the UK (hardy to around −10 °C), and it tolerates strong wind, salt spray and coastal exposure well. It dislikes hot, dry summers and prolonged deep frost.

Tūpare is usually a dense, much-branched shrub reaching 3–5 m tall with a similar spread, though in sheltered conditions it can become a small tree up to around 10 m. In its native New Zealand subalpine habitat it often forms impenetrable thickets with no obvious trunk. Growth is slow: seeds can take 9–12 months to germinate, and plants establish gradually — expect modest annual growth once settled, and plan for a final footprint of roughly 3 m wide.

Leatherwood should be watered regularly, allowing the soil to dry out between waterings.

To ensure optimal growth, the Leatherwood prefers bright indirect light for 6-8 hours each day. Insufficient light can result in slow growth and leaf drop, so it's important to find a well-lit location for this plant. Place it near a window, within a distance of 1 meter (3 feet), to enhance its potential for thriving.

There is no verified data on the toxicity of this plant in the records of Ploi. If any person, including yourself, a family member, or a pet, consume plant material with an uncertain toxicity level, it is advisable to seek the advice of a healthcare expert.