Euphorbia characias (zones 8 to 11). Add architectural structure and stimulating color to your garden with E. characias. Reaching a height upward of 4 feet, the upright dome of E. characias is one of the largest. Dense, chalky blue foliage brightens the garden year-round, and a vivid crown of chartreuse flowers tops the plant come spring. Grown in full sun, the shrub holds it color well through the season, only needing to be trimmed back once the stalks yellow. E. characias pairs neon colors with cooler hues for a truly modern design juxtaposition.