Mountain Willowherb
Botanical name: Epilobium chlorifolium
Synonyms: Epilobium chloraefolium
Common name(s): Mountain Willowherb
About:
Mountain Willowherb is a graceful perennial alpine herb that produces masses of attractive white flowers above compact leafy stems during summer. It forms neat clumps rather than spreading aggressively, making it one of the most ornamental of New Zealand’s native willowherbs.
Naturally adapted to cool mountain environments, it is an excellent choice for alpine gardens, rockeries and cool-climate native plantings.
Natural habitat:
Occurs naturally in subalpine to alpine habitats, growing mainly in tussock grasslands, herbfields and along stream margins near the bushline.
It favours open, sunny sites with excellent drainage and is commonly found among alpine herbs, gravels and rocky slopes.
Growing environment:
Prefers full sun or light shade in cool climates with free-draining soil. It is highly frost tolerant and performs best where summers are mild.
It dislikes prolonged heat and humidity, where it can become susceptible to powdery mildew. Raised beds, rock gardens and alpine troughs provide ideal growing conditions.
Endemic distribution:
Endemic to New Zealand.
It occurs from Mt Hikurangi, Mt Taranaki, the Central Volcanic Plateau and the main axial mountain ranges of the North Island, extending throughout the South Island’s alpine regions.
Height:
Typically 7–45 cm
Width:
Approximately 20–40 cm
Flowering:
October–April, with peak flowering from December to February
Fruiting:
October–July
Uses:
• Alpine gardens
• Rock gardens
• Native herb gardens
• Pollinator plant
• Mountain revegetation
• Scree and gravel gardens
• Botanical collections
Appearance:
Growth habit:
A clump-forming perennial herb with slender upright stems that branch mainly from the base, occasionally producing additional branching higher up.
The plant forms compact tufts rather than spreading extensively.
Stems:
Stems are green to reddish, finely hairy and typically 7–45 cm tall.
Distinct narrow lines of short hairs extend downward from the bases of the leaves, while the upper flowering stems become increasingly covered with glandular hairs.
Leaves:
Leaves are arranged opposite one another on the lower stems and become alternate within the flowering portion.
They are narrowly to broadly ovate, 1–3 cm long, with rounded bases, pointed tips and finely toothed margins. The leaf veins are prominent, and the foliage is a rich green.
Flowers:
Elegant white flowers are produced singly along the upper stems.
Each flower has four broad petals with shallow notches at their tips, surrounding yellow anthers and a white style. The flowers remain upright and provide a delicate display throughout the growing season.
Fruit:
The fruit is a long, slender capsule covered with fine glandular hairs.
When mature, it splits open to release numerous tiny seeds.
Seeds:
The seeds are small, brown and each carries a tuft of silky white hairs that allows it to be dispersed by the wind over considerable distances.
Ecology:
Mountain Willowherb is an important component of New Zealand’s alpine herbfields and tussock grasslands.
Its flowers provide nectar and pollen for native insects, while the wind-dispersed seeds enable it to colonise disturbed alpine gravels and stream margins.
The species is well adapted to harsh mountain climates with prolonged snow, frost and strong winds.
Associated habitats:
Subalpine and alpine tussock grasslands, herbfields, stream margins, scree slopes, gravel terraces and open mountain shrublands.
Associated species commonly include snow tussocks, Celmisia, Raoulia, Ourisia, alpine buttercups, mountain daisies and other native alpine herbs.
How to grow:
Plant in full sun or light shade in very free-draining soil. Rockeries, alpine troughs and raised gravel beds are ideal.
Keep plants evenly moist during active growth but avoid waterlogged conditions. In warmer regions, provide good air circulation and protection from excessive summer humidity.
Remove spent flower stems to encourage a tidy appearance and allow natural reseeding where desired.
Propagation:
Propagation is straightforward from fresh seed or by dividing established clumps.
Fresh seed germinates readily when sown onto a free-draining seed-raising mix and lightly covered. Small rooted divisions establish quickly when transplanted into cool, well-drained sites.
Cultural use:
Mountain Willowherb is valued as one of New Zealand’s attractive alpine wildflowers and is widely cultivated by native plant enthusiasts and alpine gardeners.
Its delicate white flowers and compact habit make it a popular species in specialised alpine collections.
Garden value:
Mountain Willowherb is an outstanding native perennial for cool-climate gardens, alpine collections and rockeries. Its neat clumps of green foliage are complemented by elegant white flowers over a long flowering season.
Its compact growth, hardiness and suitability for free-draining gardens make it an excellent choice for adding a touch of New Zealand’s alpine flora to cultivated landscapes.