Narrow-petalled Sundew

Botanical name: Drosera stenopetala
Synonyms: None
Common name(s): Sundew, Narrow-petalled Sundew

About:
Drosera stenopetala is a small perennial carnivorous herb and the only sundew species endemic to New Zealand. It forms a compact rosette of upright, spoon-tipped leaves covered with glistening glandular hairs that capture and digest small insects. The plant is adapted to cold, permanently wet montane and alpine environments and survives winter through a dormant underground rhizome.

Natural habitat:
Occurs in montane to subalpine peat bogs, tarn margins, shallow pools, seepages, wet rock faces and beside slow-flowing streams. It grows in permanently saturated, acidic ground where nutrients are extremely limited.

In the colder southern part of its range it may descend to sea level, including on the subantarctic islands.

Growing environment:
Requires cool temperatures, high humidity and constantly moist to wet acidic soil. It grows in full sun or bright open conditions but benefits from protection against excessive heat.

The species is highly frost tolerant and adapted to winter snow and freezing conditions. It does not tolerate warm, dry climates, alkaline soil, fertiliser, ordinary potting mix or mineral-rich water.

Endemic distribution:
Endemic to New Zealand. In the North Island it is uncommon and occurs mainly in the central ranges and from the volcanic plateau southwards. It is more widespread through the South Island and also occurs on Stewart Island/Rakiura, the Auckland Islands and Campbell Island/Motu Ihupuku.

Height:
Leaves approximately 3–8 cm tall; flowering stems may reach 10–20 cm

Width:
Approximately 4–10 cm per rosette

Flowering:
December–February

Fruiting:
Summer to early autumn

Uses:
• Conservation collections
• Specialist carnivorous plant displays
• Alpine and wetland botanical gardens
• Educational planting
• Study of endemic plant evolution
• Indicator of healthy alpine wetlands

Appearance:
Growth habit:
A small rosette-forming perennial arising from an underground rhizome. Its appearance changes noticeably through the growing season.

New spring growth begins as a flat rosette of approximately ten short leaves with relatively broad petioles. As the season progresses, the leaves become increasingly upright and develop longer, narrower stalks. Toward dormancy, the leaves shorten again before dying back.

Rhizome:
The plant survives winter as an underground rhizome or compact dormant growing point. This structure remains protected beneath moss, peat or saturated soil while the exposed foliage disappears.

Leaves:
The mature leaves have narrow, smooth petioles that may reach approximately 8 cm long. Each petiole ends in a rounded or spoon-shaped blade up to about 15 mm long.

The leaf blades are densely covered with long, reddish glandular hairs. The petioles often curve inward slightly, while the mature leaves are held characteristically upright.

Carnivorous glands:
The glandular hairs secrete clear, sticky mucilage that traps small flies, midges and other invertebrates. When prey is captured, nearby tentacles may bend inward to hold it against the digestive surface.

Enzymes break down the insect’s soft tissues, allowing nitrogen, phosphorus and other nutrients to be absorbed through the leaf.

Flowers:
A single white flower is usually produced on a smooth, upright stalk rising well above the leaves. The flower stalk may reach approximately 20 cm tall.

The five petals are white, sometimes with a faint yellow-green tint near their bases. They are narrow at the base and widen into wedge-shaped or rounded tips. The species name refers to these comparatively narrow petals.

Fruit:
The fruit is a small dry capsule that develops above the remains of the flower.

Seeds:
Seeds are minute and dark brown to black. They are produced in the capsule and dispersed mainly by wind, with water movement likely assisting local spread through bogs and stream margins.

Ecology:
This species is an obligate wetland plant and is closely associated with cold, permanently saturated environments. Its carnivorous habit allows it to survive in highly acidic peat where available mineral nutrients are scarce.

It contributes to the specialised biodiversity of alpine bogs, tarns and seepages. Its flowers may be visited by small insects, while its trapping leaves capture tiny invertebrates active close to the wet ground.

The plant is strongly seasonal. Leaves emerge after winter dormancy, become upright during active summer growth and then shorten as the plant prepares to retreat underground.

Because it depends on cool temperatures, clean water and stable wetland hydrology, its presence can indicate a relatively intact alpine or subalpine wetland ecosystem.

Associated habitats:
Alpine peat bogs, tarn margins, seepages, wet rock faces, shallow pools, saturated moss beds and slow-flowing stream margins. Associated species may include sphagnum mosses, cushion plants, sedges, rushes, alpine herbs, bladderworts and Drosera arcturi.

How to grow:
This is a very difficult species to cultivate and is best maintained only by experienced carnivorous plant growers or specialist conservation collections.

Grow in a cool position using an acidic, nutrient-poor medium such as live sphagnum moss or a mixture of unfertilised peat and washed silica sand. Keep the root zone permanently moist with rainwater, distilled water or reverse-osmosis water.

Provide bright light while protecting the plant from excessive summer heat. A genuine cold winter dormancy is essential. During dormancy, reduce standing water slightly but never allow the rhizome or medium to dry out.

Do not use fertiliser, lime, compost, ordinary potting soil or mineral-rich tap water.

Propagation:
Propagation is difficult and is generally attempted from fresh seed. Surface-sow the minute seed onto moist acidic medium without covering it.

Cold, moist stratification may help break dormancy. After chilling, maintain the seed in bright light under cool, humid conditions. Germination may be slow and irregular, and seedlings are extremely delicate.

Division or leaf propagation may sometimes be attempted with established cultivated plants, but success is uncertain and disturbance can easily damage the rhizome.

The species is not commercially available and must never be removed from the wild.

Cultural use:
No specific traditional Māori uses are widely documented. As New Zealand’s only endemic sundew, it is an important part of the country’s botanical heritage and a distinctive example of adaptation to nutrient-poor alpine wetlands.

The name Drosera comes from a Greek word meaning “dewy”, referring to the glistening mucilage on the leaves. The specific name stenopetala means “narrow-petalled”.

Garden value:
A rare and fascinating species of considerable botanical and conservation value. Its upright glistening leaves, delicate white flower and strict adaptation to cold alpine wetlands make it especially suitable for specialist displays and scientific collections.

Because it is extremely demanding, unavailable commercially and vulnerable to disturbance, it is best appreciated in its natural habitat or in carefully managed conservation collections.