Pink Pine

Botanical name: Halocarpus biformis
Synonyms: Podocarpus biformis, Dacrydium biforme
Common name(s): Pink pine, Yellow pine, Alpine tarwood

About:
An endemic New Zealand conifer of montane and subalpine forests and scrublands. Halocarpus biformis is an exceptionally slow-growing, long-lived member of the podocarp family, usually appearing as a low, spreading shrub in exposed alpine environments but capable of developing into a small tree up to about 10 m tall in sheltered forest.

One of its most distinctive characteristics is its dramatically different juvenile and adult foliage. Young plants have soft, narrow, needle-like leaves, while mature shoots abruptly change to densely overlapping, scale-like foliage. The species is also notable for its extremely durable, sweetly scented timber and high natural resin content.

Natural habitat:
Montane to subalpine forest, scrub, shrubland, bog margins and open alpine scrub. It is particularly characteristic of cool, high-rainfall environments and often occupies acidic, nutrient-poor or poorly drained ground where competition from faster-growing trees is reduced.

In the North Island it is predominantly a high-altitude species, while in the cooler southern South Island and Stewart Island/Rakiura it occurs at progressively lower elevations and can approach sea level.

Growing environment:
Frost, Cold, Wind, Sun, Partial Shade & Wet Soil tolerant. Best suited to cool climates and moist, acidic to neutral soils. Although naturally common on infertile and sometimes poorly drained ground, plants may develop more strongly on moist, well-drained soils with moderate fertility.

Endemic distribution:
Endemic to New Zealand.

North Island populations occur discontinuously from the Coromandel Range through the Raukūmara Range, Te Urewera, Central Volcanic Plateau and Kaingaroa Plain south through the Ruahine and Tararua ranges.

In the South Island it occurs predominantly west of the Main Divide from the Kahurangi Range south through Westland and Fiordland, with more scattered populations around Otago, Mount Cargill and the Catlins. It also occurs on Stewart Island/Rakiura.

Height:
Usually 1–5 m; occasionally up to approximately 10 m in favourable sheltered forest conditions.

Width:
Variable. Exposed plants frequently develop into broad, spreading shrubs several metres across, while forest-grown specimens may develop a more upright tree form.

Flowering:
Not applicable – gymnosperm producing pollen cones rather than true flowers. Male and female reproductive structures occur on separate plants.

Fruiting:
February – April.
Female plants produce small black seeds approximately 2–3 mm long associated with a swollen, fleshy orange receptacle.

Uses:
• Native alpine and subalpine gardens
• Ecological restoration
• High-country revegetation
• Bog and wetland-margin planting
• Native conifer collections
• Wildlife habitat and food
• Shelter in exposed cool-climate sites
• Historically used for fence posts, sleepers and building blocks
• Specialist woodworking and turning
• Scientific and dendrochronological research
• Historically investigated as a source of manool

Its timber is exceptionally durable, fine-grained, strong and pleasantly scented, but the very slow growth of the species and conservation of natural forests make it unsuitable as a conventional modern timber crop.

Appearance:
Growth habit:
A dioecious evergreen shrub or small tree with spreading branches and often a dense, rounded crown. Plants growing in exposed subalpine environments commonly become compact, spreading and cypress-like, while sheltered forest plants can develop a distinct trunk and reach considerably greater heights.

The trunk may reach approximately 0.3–0.6 m in diameter. Bark ranges from silvery-grey and grey-brown to dark brown and flakes away in small patches, often revealing distinctive reddish-brown markings beneath. The wood itself has a pinkish to yellow-brown colour.

Leaves:
Foliage is strongly dimorphic, with an abrupt transition between juvenile and adult leaves.

Juvenile foliage consists of soft, narrow, linear leaves approximately 10–20 mm long and 1.5–3 mm wide. They are pointed, sometimes with a tiny terminal point, and have a short, broad, twisted petiole. The midrib and lines of stomata are usually visible.

Adult foliage is completely different. Leaves are reduced to densely overlapping scales approximately 2 mm long. They are appressed tightly against the branchlets, rhomboid in outline, prominently keeled and have translucent margins. The resulting branchlets resemble those of a small cypress or some whipcord hebes.

Reversion shoots may occasionally produce juvenile-type foliage on otherwise mature plants.

Flowers:
True flowers are absent.

Male plants produce solitary terminal pollen cones approximately 4 mm long, usually little wider than the branchlet carrying them.

Female reproductive structures occur on separate plants, usually singly or in pairs toward the ends of branchlets.

Fruit:
As a conifer, Halocarpus biformis does not produce true fruit. Female plants instead produce exposed seeds associated with a swollen fleshy receptacle.

At maturity the receptacle becomes succulent and orange, contrasting strongly with the dark foliage. The mature seed is approximately 2–3 mm long, black, compressed and roughly oblong.

Ecology:
Pink pine is an important component of cool montane and subalpine vegetation, particularly on sites where low fertility, high rainfall, exposure or poor drainage restrict taller forest species.

Its dense growth can contribute structure and shelter to subalpine scrub communities. The fleshy structures associated with the seeds attract fruit-eating animals, particularly birds, which assist seed dispersal.

It is an exceptionally slow-growing and potentially very long-lived conifer. Individual trees may survive for many centuries, making old specimens useful for dendrochronology and studies of past environmental and climatic conditions.

The species can be confused with bog pine (Halocarpus bidwillii). Pink pine generally has thicker final branchlets approximately 3–4 mm across and prominently keeled adult scale leaves. H. bidwillii has much more slender branchlets, usually around 1–1.5 mm across, scale leaves that are scarcely or not keeled, and white rather than orange fleshy seed structures.

It can also superficially resemble Manoao colensoi and species of Lepidothamnus, but these have a more gradual transition between juvenile and adult foliage.

Associated habitats:
Montane forest, subalpine forest, subalpine scrub, shrubland, bog margins, poorly drained forest, alpine margins, high-rainfall forest and exposed rocky or infertile ground.

It may occur with other cool-climate podocarps and conifers including Halocarpus bidwillii, Lepidothamnus intermedius, Manoao colensoi and Dacrydium cupressinum, depending on locality and elevation.

How to grow:
Pink pine is best suited to cool, moist environments. Choose a position in full sun to partial shade with reliable moisture. Although naturally capable of surviving extremely poor and wet soils, cultivation does not require deliberately harsh conditions.

A moist, humus-rich but reasonably well-drained acidic to neutral soil should encourage better establishment and growth. Avoid excessively hot, dry sites, particularly in warmer districts.

Plants are naturally extremely tolerant of cold, frost and exposure once established. Growth should be expected to be slow, particularly during establishment.

Its naturally compact habit makes it particularly suitable for cool-climate native gardens, alpine plantings and sites where a small, exceptionally hardy native conifer is required.

Propagation:
Propagation is primarily from seed, although suitable juvenile material may potentially be propagated vegetatively.

Collect mature seed from female plants when the fleshy receptacle has developed its characteristic orange colour and the seed has become black. Remove the fleshy material and sow fresh seed into a moist, free-draining propagation medium.

Germination may be slow and irregular, so trays should be retained and kept consistently moist rather than discarded if germination does not occur quickly. Seedlings should be protected from drying out during their early development.

Because male and female cones are produced on separate plants, isolated specimens cannot produce viable seed without a plant of the opposite sex sufficiently close for pollination.

Cultural use:
No widely established Māori name or extensive traditional use is documented for Halocarpus biformis. Its predominantly montane and subalpine distribution may have contributed to it being less frequently encountered than many lowland forest trees.

Its durable timber was subsequently valued by European settlers for applications requiring resistance to decay, including fence posts, railway sleepers and house blocks.

Garden value:
A fascinating native conifer for cool-climate gardens, particularly where a naturally compact, slow-growing and extremely hardy species is desired. Young plants provide attractive narrow juvenile foliage before eventually developing the distinctive tightly overlapping scale foliage of maturity.

In exposed positions it can form a dense, sculptural shrub resembling a miniature cypress, making it particularly effective in native rock gardens, alpine plantings, wetland margins and naturalistic high-country landscapes.

Its exceptionally slow growth means it is not a plant for rapid screening, but this same characteristic makes established specimens valuable long-term features. For restoration planting, it is especially appropriate where the objective is to reconstruct naturally occurring montane or subalpine vegetation.