Mountain lacebark

Botanical name: Hoheria lyallii
Synonyms: Plagianthus lyallii, Gaya lyallii, Gaya lyallii var. ribifolia, Gaya ribifolia
Common name(s): Mountain lacebark

About:
A graceful deciduous native tree of the drier mountain regions of the South Island, producing masses of white flowers against softly hairy green foliage. Hoheria lyallii usually grows as a small spreading tree up to about 8 m tall and is one of New Zealand’s relatively few fully deciduous trees.

It is closely related to Hoheria glabrata, but generally occupies drier eastern mountain environments and has shorter, more densely hairy leaves that are often more deeply lobed. The flowers are large and showy, with white petals, pink styles and often purple anthers.

Natural habitat:
Montane to subalpine environments, especially upper forest margins, open mountain forest and scrub.

It also occurs on river and stream terraces, where it may form locally conspicuous groves.

The species is particularly associated with cooler, drier eastern mountain districts rather than the wetter western habitats favoured by Hoheria glabrata.

Growing environment:
Frost, Sun, Cold, Wind & Damp Soil tolerant. Best in cool climates with moist but well-drained soil. Dislikes prolonged humidity and performs poorly in warm climates without adequate winter chilling.

Endemic distribution:
Endemic to the South Island of New Zealand.

Most commonly found in eastern Marlborough and Canterbury, with a disjunct population in the Kahurangi National Park area of Nelson.

Height:
Up to approximately 8 m tall, commonly around 4–6 m.

Width:
Approximately 3–6 m depending on age, site and growing conditions.

Flowering:
November – March
Produces white flowers singly or in small clusters of 2–3 from the leaf axils.

Fruiting:
April – July
Produces dry, flattened mericarps with narrow papery wings that are dispersed by wind.

Uses:
• Specimen tree
• Cool-climate native gardens
• Mountain and high-country restoration
• Upper forest-margin planting
• Riparian planting
• Stream and river terrace restoration
• Pollinator gardens
• Seasonal-interest planting
• Traditional fibre source
• Native woodland gardens

Appearance:
Growth habit:
A slender, deciduous small tree with an open, spreading crown.

Young stems, foliage and flower structures are characteristically covered in fine star-shaped hairs, giving the plant a softer appearance than Hoheria glabrata.

The tree loses its foliage during winter and produces a fresh flush of green growth in spring.

Leaves:
Juvenile leaves are approximately 13–40 mm long and 15–40 mm wide, broadly elliptic to almost circular and usually deeply lobed or strongly crenate.

Adult leaves are larger, approximately 33–156 mm long and 22–89 mm wide, elliptic to somewhat triangular in outline. Their bases are cordate to weakly truncate, while the tips are acute to subacute.

The margins are crenate or double-crenate and are frequently more deeply lobed than those of Hoheria glabrata.

Both upper and lower leaf surfaces are usually moderately to densely covered in fine stellate hairs, one of the species’ most useful distinguishing features.

Flowers:
Flowers are produced singly or in small cymose clusters of 2–3 from the leaf axils.

Each flower usually has five, occasionally six, broad white petals approximately 16–20 mm long.

The flower centres contain around 35–50 stamens with white filaments, while the anthers can appear violet-purple. The styles are pink and provide a subtle contrast against the white petals.

The calyx is densely hairy and divided into 5–6 triangular lobes.

Fruit:
The fruit separates into several flattened mericarps.

Each mericarp has a broadly elliptic body approximately 5–6 mm long and a narrow papery wing along the upper portion.

Mature seeds are orange-brown, semicircular to triangular and usually separate from the surrounding mericarp when fully ripe.

The lightweight winged fruits are dispersed by wind.

Ecology:
Hoheria lyallii is adapted to cool, seasonally cold mountain environments and is a characteristic species of upper forest margins and disturbed montane sites.

Its deciduous habit enables it to tolerate severe winter conditions, while the dense covering of hairs on the leaves and young shoots may help reduce moisture loss and protect tissues from cold and exposure.

The large white flowers provide resources for bees, flies, butterflies and other insects.

Wind-dispersed fruits allow the species to colonise open river terraces, forest margins and disturbed ground.

Associated habitats:
Montane forest, subalpine forest margins, mountain scrub, river terraces, stream terraces, open woodland and other cool upland environments.

It is especially characteristic of drier eastern South Island mountain landscapes.

How to grow:
Best suited to cool-climate gardens.

Plant in full sun or light partial shade in moist, fertile, well-drained soil. It performs particularly well beside streams, on cool slopes and in situations with good winter chilling.

Although moisture is important during establishment, avoid stagnant or permanently waterlogged soils.

The species is strongly frost hardy once established but dislikes prolonged summer humidity and excessive warmth.

In warmer districts flowering may be poor unless plants receive sufficient cold exposure during winter.

Propagation:
Best propagated from fresh seed.

Seed can generally be sown without pretreatment, although a period of cold stratification may improve the speed and uniformity of germination.

Sow into a fine, moist, free-draining propagation mix and keep seedlings in cool, bright conditions.

Young trees establish relatively readily when planted into suitable mountain or cool-temperate conditions.

Cultural use:
The bark of Hoheria lyallii was likely used by South Island Māori as a fibre source, similar to other lacebarks.

The strong fibrous inner bark could be separated into strips and used for textiles, cordage and related purposes.

Garden value:
An excellent native specimen tree for cool and inland gardens.

Its masses of white flowers, soft hairy foliage, attractive open crown and yellow autumn colouring give it strong seasonal appeal.

Compared with Hoheria glabrata, it generally has a more softly textured appearance because of its denser leaf hairs and more deeply lobed foliage.

It is especially well suited to high-country gardens, stream margins, montane restoration and native plantings where a hardy deciduous tree is required.