| Author | (Walter) S.F. Blake | |
| Distribution | Present in the central and southern portions of the Coastal Plain, and adjacent eastern edge of the Piedmont (Franklin, Nash, and Wake counties). It is absent from the northeastern half of the province (and in VA), with no records northeast of Nash, Wilson, Lenoir, and Onslow counties. Also, it is absent from the Sandhills proper.
This is a southern Coastal Plain species, limited to eastern NC and then south throughout FL. It is thus found only in NC, SC, GA, and FL. | |
| Abundance | Uncommon to infrequent in the Coastal Plain; most numerous in well-managed conservation areas. Rare in the northeastern edge of the Piedmont. | |
| Habitat | This is a species of acidic "savanna-like" places. It occurs in wet pine savannas, wet powerline clearings near pinelands, ditches near pine stands, and borders of savannas with swamps and pocosins. | |
| Phenology | Blooms from late May to early August; fruits from June to September. | |
| Identification | This is a fairly tall and slender, wand-like herb that grows to 2-3 feet tall, generally not as tall as the similar P. leptophylla. It has only a few opposite pairs of leaves scattered along the stem, with the larger ones (along the lower stem) having blades about 3-4 inches long, tapering to the petiole; generally oblanceolate (wider above the middle), with wavy or cuneate margins. The very similar P. leptophylla has lower leaves that are slightly wider below the middle (i.e., slightly lanceolate) and generally with a more definite petiole. However, the upper two pairs of leaves are very different between these two; in P. leptophylla, these are smaller than the lower, but still about 1-inch long, much longer than the bracts in the inflorescence above. In P. purpurea, the upper pair of "leaves" are practically scales, no larger than the floral bracts, and the second highest pair is also quite small. Thus, the stem of P. purpurea generally looks quite "naked" for 1-foot or more below the lowest flowers and the lower leaves, whereas P. leptophylla has leaves that gradually become smaller toward the inflorescence. Also, the leaves of P. leptophylla are thin and flexible, often horizontally arranged, whereas leaves of P. purpurea are thick and fleshy, with the lower ones being ascending. The inflorescences of these two are quite similar, basically being a tall raceme at the end of the stem, reaching about 6 inches long or more, with the rose-pink flowers being fairly crowded; each flower is arranged horizontally, tubular with a swelling in the middle of the tube, and about 1.5 inches long. The habitats of these two are quite different; P. purpurea grows in acidic soils of wet pine savannas, ditches close to such pine stands, and other similar "savanna-like" places. P. leptophylla grows in marshy and swampy habitats, in richer soils, of tidal fresh marshes, swamp openings, and bottomlands. This species can grow in tight populations, as can others in the genus; when in bloom, the plants create a showy rose-pink mass of flowers. | |
| Taxonomic Comments | All of the U.S. Dracocephalum species have been moved to the genus Physostegia, and the scientific portion has changed from purpureum to purpurea. As the clearly different P. leptophylla was often lumped with P. purpurea in the past, some specimens labelled as "Physostegia purpurea" are actually of P. leptophylla, based on range and habitat.
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| Other Common Name(s) | Savanna Obedient-plant | |
| State Rank | S3? [S3S4] | |
| Global Rank | G4G5 | |
| State Status | | |
| US Status | | |
| USACE-agcp | FACW link |
| USACE-emp | FACW link |
