These North America native plants have many fine qualitiesbut common name notwithstanding, obedience isn't one of them: Most are notoriously invasive when growing in moist, fertile soil. Keep that in mind when choosing a site, and don't let them spread into wild areas. Slender, upright stems carry medium green, oblong, 3- to 5-in. leaves with toothed edges and pointed tips. Dense spikes of funnel-shaped, 1-in. flowers in pink, rose, white, or lavender top the stems. Blossoms resemble snapdragons (hence the name false dragonhead) and remain in place if pushed or twisted out of position (hence obedient plant). Long-lasting cut flowers.
Spiky form makes these plants useful in composing borders. Combine with summer phlox (Phlox paniculata), asters, patrinia, Japanese anemone (Anemone hybrida), false aster (Boltonia). Tall bloom stalks may need staking. Cut to ground after bloom; divide every two years to keep plants in bounds.
P. angustifolia. Native to Texas, Illinois, Mississippi. Grows 26 ft. tall, 23 ft. wide; tallest in swampy conditions, where plant forms thick colonies. Pink-purple flowers on 4- to 6-in. spikes in spring and summer.
P. pulchella. Native to eastern Texas. Grows to 2 ft. tall (taller if kept moist), 1 ft. wide. Bears spikes of rosy purple flowers in spring and summer.
P. virginiana. Native to the eastern U.S. To 4 ft. or taller, 2 ft. wide. Flowers are borne on 10-in. spikes from mid- or late summer into autumn. Rose-pink 'Bouquet Rose' grows 3 ft. tall. 'Miss Manners' has pure white blooms and forms a neat clump 22 ft. high; it spreads to 3 ft. or a little wider rather than running aggressively. 'Pink Manners' is similar but has pink flowers and grows to 3 ft. tall. Selections to about 2 ft. tall include white 'Summer Snow'; bluish pink 'Variegata', with white-edged leaves; and rose-pink 'Vivid'. 'Crystal Peak' has sturdy stems of white flowers reaching 1215 in. high.