Caulophyllum Thalictroides. Blue Cohosh is a woody herbaceous perennial with creates an airy delicate canopy of leaves in spring. The leaves can have a slight purple hue when young but mature to green. The flowers are small and greenish but it is the attractive blue berries that follow them that make this plant a great woodland addition. the berries are not edible but the native Americans have used the roots as a herbal medicine for a range of aliments and as a general tonic.  Part to full shade. 60cm.