The dramatic lavender-pink flower spikes of obedient plant appear in late summer.
Obedient plant is a stiffly erect perennial that grows from creeping rhizomes. Obedient plant overwinters as a basal rosette of willowlike leaves; during the growing season wandlike square stems emerge and bear leaves in opposite pairs. The leaves are narrow, 2-6 in (5.1-15.2 cm) long, smooth-surfaced, toothed along the edges, dark green above and lighter green below. The pale lavender-pink flowers are borne in showy spikes atop 2-4 ft (0.6-0.9 m) stalks in late summer and fall. The tubular 1 in (2.5 cm) blossoms are arranged in vertical columns along the flower spike and the lower ones open first. Each flower has a two-lobed upper lip and a spotted three-lobed lower lip. The flower bearing stems are usually unbranched, but they may have one or two forks near the top. The weakly three-sided 1/8 in (0.3 cm) nutlets that ripen in the fall are brown and have smooth dull surfaces. Cultivated forms have been selected to produce plants with short bushy form and especially showy flowers. 'Vivid' is a vigorous grower which bears plentiful clusters of rose-lilac blossoms; 'Variegata' is a fancy border plant with variegated leaves and pink flowers; 'Rose Queen' is a 2 ft (0.6 m) plant with rose-pink flowers; 'Bouquet Rose' grows to 3 ft (0.9 m) with shell-pink flowers; 'Rosea' grows to 4 ft (1.2 m) and has pink flowers; the flowers of 'Pink Bouquet' are rose colored; those of 'Summer Glow' are a rosy crimson color. 'Summer Snow' bears an abundance of neatly arrayed sparkling white flowers on 2 ft (0.6 ft) plants, but it is far less assertive than the pink-flowered varieties and does not hold its own as well in a mixed meadow. 'Alba' and 'Crown of Snow' also have white flowers.
Obedient plant is native to eastern North America from Quebec to Manitoba, and south to Texas, Louisiana, Alabama and Georgia. Obedient plant occurs in swamps, streambanks, ditches, seepages, damp meadows and prairies, moist open woodlands, bogs, and pine savannas.
Lightly acid sandy loam is probably the best soil type for Physostegia virginiana, but it will grow on a variety of moist soils. Anywhere in the pH 5-7 range is fine. Fertilize often during the growing season and mulch well in the fall in cold climates. Divide every 2-3 years in the spring. Light: Obedient plant is happy in either sunny or lightly shaded spots, but it does best with some shade on drier sites, and full sun where it is wetter. Moisture:Physostegia likes moist soil. Low spots and wetland edges that flood occasionally are fine. It will even be happy in soil that is saturated much of the time, but it will be less invasive and have sturdier stems under drier conditions. Hardiness: USDA Zones 3 - 9. Propagation: Obedient plant can be sown outdoors in spring or summer (up to two months before the first frost) or indoors anytime. For best germination rates, sow in the fall as soon as the seeds are ripe. Sow them where they are to grow or leave the flats outdoors for three months of damp stratification at about 40ºF (4.4ºC). Seedlings will appear a few weeks after spring temperatures rise into the 70ºF (21ºC) range. Indoors, use a rich loamy soil mix and keep it moist and around 70-75 F (21-24ºC). Germination will occur in 1-4 weeks. Seedlings will flower their second year. You can produce blooming plants faster by taking 2-3 in (5.1-7.6 cm) cuttings of young shoots in the spring and rooting them in a coldframe. It is safest to divide Physostegia in the spring. In mild climates you can divide them in the early fall, then protect the new plants with mulch. Replant only the vigorous outer roots.
Several varieties of obedient plant that have white flowers are available.
Usage Physostegias are widely used in wildflower meadows and water garden fringes, as well as in more civilized borders. The blossoms are long lasting as cut flowers. They are especially easy to arrange because flowers pushed to face a different direction from the stem will stay in their new positions obediently, which is where the plant got its name.
This is a wonderful plant to add luminous rosy lavender late season color to the bronzy golds and yellows of a damp meadow. It holds its own with grasses very well. And it is classified as deer resistant, so it should bloom well in places where deer would eat the tasty buds off other flowers.
Obedient plant can be an aggressive colonizer, especially on rich moist sites. To keep it a genuinely obedient plant, pick a place with drier soil and cut down on the fertilizer.