This favorite of the Monarch butterfly produces a profusion of sweet-scented lavender flowers in mid-summer. The caterpillars feast on the leaves, stocking up for the day when they will become butterflies and migrate to Mexico for the winter. Grows readily from seed, and thrives in almost any well-drained soil, even tough clay or dry sand. Spreads rapidly by rhizomes, and is best planted in large areas with other grasses and flowers. Grows two to four feet tall. Hardy to Zones 3 - 8.