Grass Lily

Botanical name: Herpolirion novae-zelandiae
Synonyms: None
Common name(s): Grass lily, Sky lily

About:
A tiny, creeping perennial herb that forms low, grass-like swards of narrow leaves, punctuated in summer by disproportionately large, delicate white to pale blue, violet or lavender flowers. Herpolirion novae-zelandiae is an attractive little plant of open, damp ground, particularly in montane, subalpine and alpine environments.

Despite its grass-like appearance, it is not a grass. Plants spread through slender underground stems, producing repeated tufts of leaves and eventually forming extensive patches close to the ground.

Natural habitat:
Occurs primarily in open, damp montane to alpine habitats, including wet grassland, herbfield, boggy ground, seepages, tarn margins and other areas where soils remain moist.

It is particularly characteristic of cool, open environments where competition from taller vegetation is limited.

Growing environment:
Frost, Sun, Cold, Moist Soil & Alpine tolerant. Prefers consistently moist ground with good light and cool conditions. It can occur in both wetland and non-wetland habitats but does not favour prolonged drying.

Endemic distribution:
Indigenous but not endemic to New Zealand, also occurring in Australia.

Within New Zealand it is principally a plant of montane, subalpine and alpine environments of the North and South Islands.

Height:
Approximately 1–6 cm tall, with flowering structures remaining close to the foliage.

Width:
Individual tufts are only a few centimetres wide, but creeping underground stems allow colonies to spread considerably and form extensive grass-like swards.

Flowering:
November – February
Flowers are white, pale blue, violet or lavender-blue and remarkably large relative to the size of the plant.

Fruiting:
December – March
Produces small capsules containing smooth, glossy black seeds.

Uses:
• Alpine gardens
• Native rockeries
• Bog and wetland gardens
• Tarn-margin planting
• Specialist native collections
• Alpine troughs
• Moist groundcover
• Ecological restoration of suitable upland habitats
• Botanical and educational collections

Appearance:
Growth habit:
A very small, creeping perennial herb spreading through slender underground stems approximately 1–2 mm in diameter.

These stems produce closely spaced tufts of foliage, allowing established plants to develop into extensive low swards resembling very fine grass.

Leaves:
Leaves are crowded into flattened tufts, usually with around 6–8 leaves arising together.

The blades are approximately 1–6 cm long and 1.5–2.5 mm wide, occasionally reaching about 4 mm. They are somewhat fleshy, often distinctly glaucous or blue-green, longitudinally folded and strongly keeled toward the base.

The leaf bases form sheaths up to approximately 1 cm long with conspicuous longitudinal veins.

Flowers:
Flowers are almost sessile and emerge from amongst the short foliage, surrounded at their base by several short, sheath-like leaves.

Each flower is surprisingly large for such a diminutive plant, with six spreading tepals approximately 11–15 mm long. Colour varies from white through pale sky-blue to violet or lavender, often producing a striking contrast against the grass-like foliage.

The six stamens are approximately half the length of the tepals. Their filaments broaden toward the base, where they are yellowish and finely hairy.

Fruit:
The fruit is a small capsule approximately 6.5 mm long when fresh, becoming around 4 mm long when dry.

As the capsule matures it becomes deeply grooved and eventually splits open to release the seeds. Seeds are approximately 2.2 mm long, somewhat flattened, smooth, black and glossy.

Ecology:
Its creeping underground stems allow grass lily to gradually occupy suitable open ground and recover vegetatively following minor disturbance.

The low stature and compact foliage are well adapted to exposed mountain environments where plants experience strong winds, frost and short growing seasons.

The relatively conspicuous flowers are held immediately above the foliage during the warmer months. Following fertilisation, capsules develop close to the ground and eventually open to release their seeds, which are dispersed principally by wind.

Associated habitats:
Montane grassland, subalpine herbfield, alpine turf, bog margins, seepages, wet depressions, tarn margins, open wetland vegetation and other cool, permanently or seasonally damp sites.

How to grow:
Best grown in a cool, open position with consistently moist soil.

A humus-rich but aerated substrate that remains damp without becoming stagnant is suitable. In cultivation, alpine troughs, moist rockeries and the margins of small ponds or bog gardens can provide appropriate conditions.

Full sun is suitable in cool climates, although some protection from intense lowland summer heat may be beneficial.

Because of its naturally small stature, it should not be planted beside vigorous groundcovers that can quickly overwhelm it.

Propagation:
Propagation can be achieved from seed or by division of established creeping plants.

Fresh seed can be sown onto a fine, moist propagation medium and kept under cool, bright conditions. Seedlings should be protected from drying because of their extremely small size.

Division is useful once a healthy colony has developed. Small sections containing underground stems, roots and several leaf tufts can be carefully separated and replanted into permanently moist substrate.

Cultural use:
No significant traditional Māori practical uses are widely documented for Herpolirion novae-zelandiae.

The botanical name Herpolirion means “creeping lily”, referring to the plant’s spreading underground stems and lily-like flowers.

Garden value:
A beautiful miniature native for specialist alpine, wetland and rock gardens.

The combination of fine grass-like foliage and comparatively large sky-blue, violet or white flowers gives Herpolirion novae-zelandiae considerable ornamental appeal despite its tiny size.

It is particularly effective planted between rocks, along the edge of a damp alpine trough or allowed to form a small naturalistic sward where its summer flowers can be appreciated at close range.