Astrantia carniolica ‘Rubra’ Astrantias are superb perennials for growing under trees, on a stream bank or in a moist border. They prefer moist soils but will tolerate drier conditions as long as the plants are mulched. Astrantia carniolica ‘Rubra’ is a dwarf variety, growing no taller than 45cm. It bears rich maroon-coloured flowers and bright green bracts.