Shore Spurge

Botanical name: Euphorbia glauca
Synonyms: None
Common name(s): Shore Spurge, Sea Spurge, Waiū-atua, Waiū-o-Kahukura, Sand Milkweed

About:
Shore Spurge is a striking perennial coastal herb recognised for its attractive blue-grey foliage, reddish stems and distinctive deep red flower cups. It is one of New Zealand’s most ornamental coastal plants and is naturally restricted to exposed shorelines, dunes and rocky coastal slopes.

Like all spurges, it produces a milky white sap that can irritate the skin and eyes. Despite its toughness, Shore Spurge has declined significantly throughout much of its range and is now considered a threatened native species.

Natural habitat:
Occurs naturally on coastal cliffs, rocky headlands, talus slopes, sand dunes, coastal banks and rocky lake shore scarps.

It grows in open, sunny sites where competition from larger vegetation is limited and is well adapted to salt spray, strong winds and freely draining soils.

Growing environment:
Thrives in full sun and free-draining sandy, gravelly or rocky soils. It is highly tolerant of coastal winds, salt spray and drought once established.

The species performs best in open coastal situations and dislikes heavy, poorly drained soils or prolonged shade.

Endemic distribution:
Endemic to New Zealand, including the Chatham Islands.

It occurs around much of the coastline but is often localised and has declined in many regions.

Height:
Typically 50 cm–1 m

Width:
Approximately 50 cm–1 m, spreading slowly by underground rhizomes

Flowering:
September–March, with occasional flowering throughout the year

Fruiting:
December–July

Uses:
• Coastal restoration
• Dune stabilisation
• Native coastal gardens
• Erosion control
• Wildlife habitat
• Feature foliage plant
• Botanical collections

Appearance:
Growth habit:
A robust perennial herb with numerous upright stems arising from creeping underground rhizomes.

It gradually forms attractive colonies while remaining well suited to exposed coastal conditions.

Stems:
The stems are stout, smooth and reddish to reddish-green, emerging annually from the underground rhizome system.

When damaged they exude a copious white milky sap.

Leaves:
Leaves are alternately arranged and have a distinctive blue-green to glaucous colour.

They are thick, fleshy and elongated with a smooth surface, helping the plant conserve moisture in harsh coastal environments.

Flowers:
The true flowers are tiny but are surrounded by conspicuous deep red cup-shaped structures known as cyathia.

These colourful floral displays are produced in dense terminal clusters and create a striking contrast with the blue-grey foliage.

Fruit:
Following flowering, small three-lobed capsules develop and eventually split open to release the seeds.

The fruit matures from early summer through winter.

Seeds:
Seeds are naturally dispersed by both wind and water, allowing the species to colonise suitable coastal habitats. Fresh seed germinates readily under suitable conditions.

Ecology:
Shore Spurge is an important component of New Zealand’s coastal ecosystems, where it helps stabilise dunes, rocky slopes and coastal banks.

Its flowers provide nectar for insects, while its dense root system assists in binding loose soils. The species is naturally adapted to salt spray, drought and coastal exposure.

Populations have declined due to browsing by cattle, sheep, pigs and possums, habitat loss from coastal development, erosion, invasive vegetation and, in some areas, fungal disease.

Associated habitats:
Coastal dunes, rocky shorelines, cliff faces, coastal shrublands, talus slopes, gravel beaches and exposed lake shore scarps.

Associated species commonly include pīngao, spinifex, sand coprosma, taupata, shore bindweed, pōhuehue, native ice plant and other coastal herbs and shrubs.

How to grow:
Plant in full sun in a well-drained sandy or gravelly soil. It performs exceptionally well in coastal gardens and tolerates strong winds, salt spray and extended dry periods.

Avoid heavy clay soils and sites that remain wet during winter. Little maintenance is required once established.

When handling the plant, wear gloves and avoid contact with the milky sap, as it may cause skin irritation and serious

eye irritation.

Propagation:
Propagation is easy from fresh seed, semi-hardwood cuttings or by dividing established clumps.

Rooted divisions establish quickly, while fresh seed germinates readily when sown into a free-draining propagation mix.

Cultural use:
The Māori names waiū-atua and waiū-o-Kahukura refer to the plant’s distinctive milky sap.

Historically, preparations of the plant were sometimes used in traditional remedies, although great care was required because of the sap’s irritating properties.

Garden value:
Shore Spurge is one of New Zealand’s most spectacular native coastal plants, combining bold blue-grey foliage with vivid red floral displays over many months.

It is an outstanding feature plant for coastal gardens, dry landscapes and restoration projects, while also contributing to the conservation of a nationally vulnerable native species.