Euphorbia characias subsp. wulfenii is an architectural perennial, perfect for adding a touch of drama to the border. Bluish-green foliage looks fresh all year round, and in early summer it’s joined by large, dome-shaped, lime-yellow flowers that tower above it. It’s ideal for growing in a sunny border or gravel garden, and is a good planting partner for kniphofias, which bear orange and yellow flowers. For best results grow Euphorbia characias subsp. wulfenii in moist but well-drained soil, in full sun. Cut down the flower stems to ground level as the blooms fade. Be careful when handling the plant as the thick, white sap can irritate the eyes and skin.