Marsh Milkweed. Sweetly scented clusters of rose-pink flowers bloom in summer. Butterflies find the faint vanilla fragrance irresistible and monarch larvae feed on the foliage. Grows naturally in swamps and wet meadows but also grows well in the garden. Grows in full sun and moist soil. Height: 36-48 inches. Spread 34-36 inches. Deep pink/rose color. Butterfly nectar, hummingbirds. Perennial.