Black Scree Button Daisy

Botanical name: Leptinella atrata subsp. atrata
Synonyms: Cotula atrata, Cotula atrata subsp. atrata
Common name(s): Black scree button daisy

About:
Leptinella atrata subsp. atrata is an unusual endemic New Zealand alpine daisy specialised for life in unstable mountain scree.

It is a fleshy perennial herb that produces one or more compact summer-green leaf tufts from thick rhizomes buried amongst moving stones. Its most striking feature is the flower head, which is composed of numerous very dark red to almost black florets and gives the plant its common name.

Rather than forming broad mats like many other Leptinella species, it survives by anchoring itself deeply into scree with long, extensively branched fleshy roots while continually renewing shoots close to the shifting surface.

Natural habitat:
Open, mobile, sparsely vegetated subalpine and alpine scree.

It is strongly associated with unstable slopes of loose rock and gravel where few other vascular plants can survive.

Plants are generally found above approximately 1,000 m elevation.

Growing environment:
Full Sun, Alpine Exposure, Cold, Frost, Wind, Excellent Drainage, Loose Mineral Substrate & Low Competition tolerant.

Black scree button daisy is highly specialised for cool, open mountain conditions.

It requires exceptional drainage and is adapted to constant movement of surrounding stones rather than stable garden soil.

Summer moisture is important around the root zone, but prolonged waterlogging is unsuitable.

Endemic distribution:
Endemic to New Zealand.

Restricted to the eastern and inland South Island, from North Canterbury south to northern Otago.

Its distribution is associated with suitable high-elevation scree systems rather than continuous alpine vegetation.

Height:
Usually approximately 3–12 cm tall in foliage, with flowering stalks reaching up to about 12 cm.

Width:
Individual leaf tufts are small, but mature plants may spread gradually through clustered rhizome branches across approximately 10–30 cm or more.

Flowering:
November–January.

Flower heads are approximately 5–13 mm in diameter and are borne on stout fleshy peduncles that are usually only slightly taller than the leaves.

The florets are very dark red to almost black, with the upper corolla especially dark and the lower portions wine-red.

Fruiting:
January–April.

Mature cypselae are pale to dark brown, approximately 1.8–2.8 mm long, and become deeply wrinkled when ripe.

They are dispersed principally by wind and possibly by attachment.

Uses:
• Specialist alpine collections
• Scree gardens
• Rock gardens designed for alpine specialists
• Botanical conservation collections
• Educational alpine displays
• Research and ex-situ conservation
• Naturalistic high-country planting

Appearance:
Growth habit:
A fleshy, monoecious perennial herb producing compact summer-green leaf tufts amongst loose scree.

Plants commonly produce several shoots from clustered rhizome branches, but many of these die back after their first season.

Leaves are usually crowded near the rhizome apex.

Rhizomes/Stems:
Rhizomes are short, ascending and very fleshy, generally up to about 10 mm long.

Young rhizomes lie at or near the scree surface but become progressively buried as surrounding stones move and accumulate.

They are pale to pinkish-red and initially sparsely hairy before becoming more or less hairless.

Roots are numerous, very long, fleshy and extensively branched, reaching up to about 2 mm thick.

This deep, spreading root system is a key adaptation to unstable scree.

Flowering peduncles are stout, fleshy and approximately 30–120 mm long.

They carry 4–10 evenly spaced bracts that become progressively simpler toward the flower head.

Leaves:
Leaves are 2-pinnatifid and approximately 20–80 mm long by 5–13 mm wide.

The blade is about 15–60 mm long, obovate, leathery and distinctly fleshy.

Colour is grey-green, often tinged red along the main and secondary axes.

Leaves are sparsely hairy.

There are usually 8–15 pairs of primary pinnae.

The lower pinnae are more widely spaced, while the distal pinnae commonly overlap.

Secondary pinnae number up to nine per primary pinna and are oblong to obovate with rounded tips.

These smaller divisions characteristically turn upward rather than lying flat.

Flowers:
Flowers are grouped into small button-like capitula approximately 5–13 mm across.

Each head has a convex surface and hemispherical involucre.

The outer involucral bracts are thick, grey-green and often tinged pink or red, with up to six pairs of oblong lobes.

Inner bracts are thinner, simple and obovate with narrow scarious margins.

Each capitulum contains approximately 100–240 female florets arranged in several rows, together with roughly similar numbers of male florets.

The florets are approximately 3.25–3.75 mm long and range from very dark red to almost black.

The corolla teeth are conspicuous, equal and spreading.

Stigmas extend only slightly beyond the corolla and retract back into the tube after flowering.

Fruit:
The fruit is a dry cypsela approximately 1.8–2.8 mm long and 0.8–1 mm wide.

It is slightly flattened and becomes deeply wrinkled as it matures.

Colour ranges from pale brown to dark brown.

Seeds:
Each cypsela contains a single seed.

The lightweight, papery fruits are adapted primarily for wind dispersal and may also be transported when caught on passing animals or other moving material.

Ecology:
Leptinella atrata subsp. atrata is highly specialised for one of New Zealand’s harshest alpine environments.

Mobile scree repeatedly buries, exposes and damages vegetation. This species survives through its short but deeply buried rhizomes and extensive fleshy roots, which anchor the plant beneath the moving surface.

Its summer-green growth strategy allows it to take advantage of the relatively short alpine growing season before severe winter conditions return.

Low stature reduces exposure to wind, while fleshy leaves and roots help buffer the plant against rapid fluctuations in moisture.

Competition is minimal because few other plants can tolerate the same constantly shifting substrate.

Associated habitats:
Subalpine scree, alpine scree, loose rock slopes, gravel fans and sparsely vegetated high-country slopes.

Associated vegetation is generally sparse and may include other highly specialised scree herbs, cushion plants, small

alpine daisies and scattered tussocks around more stable margins.

How to grow:
Black scree button daisy is a difficult specialist species and is not suited to ordinary garden conditions.

If cultivated, it requires an open alpine position with very high light levels, cool temperatures and exceptionally free-draining mineral substrate.

A deep scree bed of coarse gravel and broken rock is preferable to conventional potting mix.

The crown should remain close to the surface while allowing roots to penetrate deeply into cooler, moisture-retentive layers.

Avoid rich soils, stagnant moisture, heavy competition and warm humid conditions.

It should never be collected from wild populations.

Propagation:
Propagation is difficult.

Fresh seed may be attempted in a coarse, sterile alpine medium under cool conditions, but germination and establishment can be slow and unreliable.

Division is generally unsuitable because the species possesses specialised fleshy rhizomes and deeply penetrating roots and strongly resents disturbance.

Propagation should therefore be undertaken only from legally sourced cultivated material or seed.

Cultural use:
No specific traditional Māori material use is well documented for Leptinella atrata subsp. atrata.

Its significance lies particularly in its remarkable adaptation to New Zealand’s unstable alpine screes and its contribution to the highly specialised flora of the eastern South Island mountains.

Garden value:
A fascinating botanical rather than conventional ornamental plant.

Its deeply divided grey-green foliage, reddish stems and almost black flower heads give it a distinctive appearance unlike most other native daisies.

It is best suited to specialist alpine collections, purpose-built scree beds and conservation cultivation where its unusual ecology can be accurately reproduced.

For most gardens, its value is best appreciated as a wild alpine species rather than as a general landscape plant.