Tall Sundew

Botanical name: Drosera auriculata
Synonyms: Drosera circinervia, Drosera stylosa, Drosera peltata subsp. auriculata
Common name(s): Tall Sundew, Climbing Sundew, Sundew

About:
Tall Sundew is a distinctive tuberous carnivorous herb with an erect, slender stem bearing alternate crescent-shaped trapping leaves. Unlike the low rosettes formed by many other sundews, mature plants may rise well above surrounding vegetation and sometimes lean or scramble through nearby plants. It grows during the cooler, wetter part of the year, flowers from spring into summer, then dies back to a small underground tuber during dry conditions.

Natural habitat:
Occurs from coastal areas to montane elevations on naturally open or recently disturbed ground. Typical habitats include clay pans, damp banks, low scrub, peatlands, lava fields, sandy ground and seasonally wet soils.

It is often especially abundant after fire or other disturbance, when competition from taller vegetation has been temporarily reduced.

Growing environment:
Prefers full sun or very bright light, acidic nutrient-poor soil and a strongly seasonal moisture regime. The soil is typically moist during active winter and spring growth but becomes considerably drier during summer dormancy.

It is intolerant of fertiliser, lime, rich compost, alkaline substrates and mineral-rich water.

Endemic distribution:
Indigenous but not endemic to New Zealand. It occurs throughout the North Island and in the South Island south to approximately South Canterbury, northern Otago and southern Westland. It is also native to Australia.

Height:
9–60 cm

Width:
Basal rosettes approximately 2–8 cm across; mature stems may spread more widely when supported by surrounding vegetation

Flowering:
September–February

Fruiting:
October–April

Uses:
• Specialist carnivorous plant collections
• Educational botanical displays
• Seasonal bog and peat gardens
• Conservation planting
• Study of post-fire vegetation and carnivory

Appearance:
Growth habit:
A perennial tuberous herb with a slender, upright and usually unbranched stem. The stem may become slightly flexuous or weakly climbing among surrounding vegetation. Plants begin the growing season as a flat basal rosette before producing their tall leafy stem.

Tuber:
The underground tuber is ovoid to globose and grows up to approximately 10 × 8 mm. It is white to reddish and is often enclosed by a thin, papery sheath. A vertical underground stolon, commonly 2–8 cm long, connects the tuber to the emerging shoot.

Basal leaves:
The basal rosette contains approximately four to nineteen leaves. Their blades are rounded, oval, kidney-shaped or elliptic and are held on narrow, flattened petioles.

Stem leaves:
The stem bears approximately nine to thirty-six alternate leaves. Each has a crescent-shaped blade with sharply pointed outer angles, held on a fine petiole up to approximately 23 mm long.

The upper surfaces and margins are covered with stalked glandular hairs tipped with sticky mucilage. Foliage is usually olive-green in open sites but may become deep maroon in strong sunlight.

Carnivorous glands:
Small insects become trapped in the glistening mucilage produced by the leaf glands. The leaf and nearby tentacles may slowly bend toward captured prey, after which digestive enzymes release nitrogen and other nutrients that are absorbed by the plant.

Flowers:
Flowers are arranged in a one-sided raceme carrying approximately two to fourteen blooms. Each flower is borne on a slender stalk and has white, pink, rose or occasionally deeper pinkish-violet petals.

The petals are obovate to wedge-shaped, approximately 3–10 mm long, and often have a shallow notch at the tip. The sepals are smooth rather than hairy, an important feature for distinguishing this species from Drosera hookeri.

Fruit:
The fruit is a small dry capsule that opens when mature to release numerous seeds.

Seeds:
Seeds are cylindrical, approximately 0.8–1.6 mm long, with a shallowly reticulated surface. Their shape and relatively large size help distinguish the species from Drosera hookeri, which usually has smaller, more deeply pitted seeds.

Ecology:
Tall Sundew is adapted to infertile soils where nitrogen and phosphorus are scarce. Its carnivorous leaves compensate for these deficiencies by capturing small flies, midges and other invertebrates.

It is also an effective pioneer of recently exposed or burned ground. Fire removes competing vegetation and creates open, sunny conditions in which dormant tubers can quickly produce new growth.

The plant follows a strongly seasonal cycle. Growth generally begins when autumn or winter rains moisten the soil. The basal rosette is followed by the erect stem, flowering and seed production. As summer dryness develops, the above-ground parts wither and the plant survives underground as a dormant tuber.

Associated habitats:
Clay pans, pakihi, peatlands, damp banks, lava fields, low scrub, open woodland, seasonally wet heathland and recently burned ground. Associated species may include sedges, rushes, low mānuka scrub, mosses, lichens and other native sundews.

How to grow:
Grow in full sun using an acidic, low-nutrient medium such as a mixture of peat and washed silica sand or perlite. Do not use fertilised potting mix or ordinary garden compost.

During active growth, keep the medium consistently moist with rainwater, distilled water or reverse-osmosis water. As the stems naturally blacken and die back, gradually reduce watering and allow the pot to become much drier during summer dormancy.

Resume watering when cooler autumn conditions return. The pot should be kept where it can experience natural seasonal temperature changes and strong light.

Propagation:
Propagation may be undertaken from fresh seed or dormant tubers. Surface-sow seed onto moist acidic medium without covering deeply. Germination generally occurs as temperatures cool and moisture increases.

Dormant tubers or small daughter tubers may be carefully separated during summer and replanted approximately 3–5 cm deep. They should be handled gently and kept only slightly moist until growth resumes.

In suitable conditions the species may self-seed and naturalise. Only nursery-propagated plants or tubers should be used, and wild populations must not be disturbed.

Cultural use:
No specific traditional Māori uses are widely documented. The species forms part of the specialised flora of repo, pakihi and other nutrient-poor wetland or open-soil habitats.

The name Drosera comes from a Greek word meaning “dewy”, referring to the sparkling droplets on the trapping leaves. The name auriculata refers to the ear-like or lobed shape of the crescent-shaped stem leaves.

Garden value:
A highly unusual carnivorous plant valued for its erect form, shimmering trapping leaves and delicate pink to white flowers. It makes an excellent subject for specialist bog gardens, carnivorous plant collections and educational displays.

Its seasonal dormancy must be understood for successful cultivation, as the apparent death of the stems in summer is a normal part of the plant’s annual cycle.