- Perennial forb with slender rhizomes.
- Opposite, simple, petiolate. Petioles 8-50 mm long, not winged at the tip. Leaf blades 1.5-7.0 cm long, heart-shaped to ovate or triangular-ovate, broadly rounded to truncate or cordate at the base, bluntly or more commonly sharply pointed at the tip, the margins finely to relatively coarsely toothed, the surfaces densely pubescent with relatively long, spreading to somewhat curved, multicellular, mostly gland-tipped hairs, the undersurface sometimes also with sessile glands.
Stem and leaves.
- Slender racemes, these mostly terminal, sometimes in a cluster of 3 from the stem tip, the flowers 2 per node, solitary in the axils of bracts, the bracts 3-9 mm long, ovate to broadly ovate, sometimes finely few-toothed.
Inflorescence axis and bracts.
- Calyces 3-4 mm long, becoming closed and enlarged to 4-6 mm at fruiting, the outer surface densely pubescent with spreading, multicellular, mostly gland-tipped hairs. Corollas 17-25 mm long, densely pubescent with short, spreading, gland-tipped-hairs on the outer surface, pale blue to blue or bluish purple above a usually white tube, the lower lip variously white with bluish purple markings or blue to bluish purple with white and purple mottling and/or spots, the tube S-shaped (bent upward just above the calyx and strongly curved or oblique at or above the throat), lacking a ring of hairs in the throat, the lateral lobes not well-developed, ascending, the lower lip broadly fan-shaped, deeply notched at the tip.
Corollas (ssp. rugosa)
Corollas (ssp. ovata)
- Persistent calyces enlarged and closed at fruiting. Nutlets 1-4 per calyx, 1.2-1.5 mm in diameter, depressed globose or broadly obovoid, the surface dark brown, densely warty or with low, rounded tubercles, these reddish brown to orangish brown.
- May - October.
- Forests, glades, streambanks, bluffs, ledges, roadsides.
- Native to the U.S.
- This small but pretty species occurs across most of Missouri, except for some northwestern counties where it is rare or absent. Its main North American distribution is in the U.S. Midwest, with scattered populations extending to the Atlantic and Gulf Coasts.
Differentiating this species from the closely related
can be challenging. The most reliable character seems to be the glabrous throats of the flowers; in
the throats of the corolla tubes are hairy. Also,
has glandular hairs on the calyces, whereas in
the hairs are usually not glandular. The leaves of
also usually have a distinctly rugose, highly textured appearance.
Some authors recognize multiple infraspecific forms within this species, though many specimens show intermediate or contradictory character states which can make reliable subspecies assignment difficult. One difference is in the color of the lower lip of the corolla. In ssp.
this is white with blue spots or mottling, whereas in ssp.
it is blue with mottled, longitudinal white bands along the midvein. Examples of these two are shown in the images above. The ssp.
has large bracts which exceed the calyces and sometimes even the flowers. All three of these forms occur in Missouri.
The common term "skullcap" comes from a fancied resemblance of the corolla to the dome of the human cranium.
Photographs taken at Shaw Nature Reserve, Franklin County, MO, 6-18-2006, Taum Sauk State Park, Iron County, MO, 8-23-2009, Weldon Spring Conservation Area, St. Charles County, MO, 6-24-2011, Meramec Conservation Area, Franklin County, MO, 6-21-2013, and Daniel Boone Conservation Area, Warren County, MO, 6-25-2013 (SRTurner).