cultivar Euphorbiaceae flower garden green natural nature perennial plant spurge summer background Greece Greek pin-cushion yellow rock rocky stony Dog's mercury England Great Britain Mercurialis perennis poisonous spring uk united kingdom wild color colorful colors croton crotone crotons landscaping leaf leaves plants shrub shrubs stem tree trees varigated Asia southeast asia abundant angles appearances castor-beans castor-oil castor-oil-plant castor-seeds cluster clusters common cotyledons fast-growing flowers foliage highly-toxic inflorescences invasive large large-leaves medicinal palm-of-Christ palma-Christi poison ricinus-communis seed-pods seedhead shrubbery spiky-green-seed-capsule spiny surface surfaces textured textures toxic toxins vegetation wasteland-weed weed widespread