When old fashioned cushion spurge, Euphorbia polychroma, was used in the past, it was mainly grown for its brilliant sulfur yellow bracts in spring. Beyond that, it didn’t hold a lot of interest in the garden. Over the past five years, many exciting new euphorbias like ‘Ascot Rainbow’ have come onto the market, and they offer season-long interest in the garden. Euphorbia isn’t just for spring anymore.
With very little effort from the gardener, ‘Ascot Rainbow’ offers three seasons of interest in the landscape. Phenomenal foliage and an ideal habit set this variety apart. Every part of this plant is variegated, even the bracts that surround the large clusters of flowers in late spring. It keeps its tight, bushy, upright habit from spring to winter without any pinching. In areas with mild winters, it can remain standing through the winter. It makes an excellent container specimen as well.
The key to overwintering ‘Ascot Rainbow’ successfully in USDA Zones 5 to 9 is having excellent drainage, especially in winter. In trials, it has overwintered very well in Zone 5 sandy soils but not in clay. This is a common trait across the genus and is not specific to ‘Ascot Rainbow’.