|This subspecies reaches about 6 inches. Fern-like leaves are silver-green, linear-shaped, and scalloped or entire. Flowerheads are flattish clusters in white. This heat and drought tolerant perennial has a fiberous root system and can become invasive. Divide annually to maintain. There are many cultivars of the garden favorite. Butterflies are attracted to this plant. Good cut flower that dries well too.