Even the few growing in Dunedin Botanic Garden represent a journey that would take you from New Zealand to Europe, to the Himalayas as well as the Canary Islands.
That is without including the succulent forms from South Africa and Kenya in the Winter Garden glasshouse.
Soft texture and glowing colours
Depending on the species, they can form bold spreading clumps or act as low ground cover, while their profusion of narrow or small rounded leaves brings a softening effect to the borders in which they grow.
Tiny male and female flowers are held in cup-like structures known as cyathia.
It is in fact, the cyathia, which vary in colour from greenish yellow to orange red, that give the flower heads real presence.
Sometimes the true flowers at the centre of the cyathia contrast in colour to give a striking two-toned effect, while an added bonus can be whorls of coloured floral leaves which boost the impact of the whole plant.
Eye-catching
One of the most spectacular species is Euphorbis characias ssp. wulfenii.
It is renowned for its robust growth habit with 1m-2m stems clothed in dense whorls of grey-green foliage.
Once established, it can send up bold heads of yellow flowers in late winter and early spring.
In the rhododendron dell, one example is growing on the free-draining edge of the euphorbia border and another is enjoying the dry conditions at the base of an old karaka in the rhododendron species border.
Not all stems will flower in the same year, but those that do should be cut back to encourage flower succession and to help maintain overall plant health and vigour.
- By Doug Thomson.
Doug Thomson is curator of the rhododendron dell at the Dunedin Botanic Garden.
