14. Hypericum sphaerocarpum Michx. (round-fruited St. John’s wort)

H. sphaerocarpum var. turgidum (Small) Svenson

Pl. 362 e, f; Map 1574

Plants perennial herbs, the rootstock and stem bases often somewhat woody, sometimes with short, poorly developed rhizomes. Stems occurring singly or more commonly 2 or more together, 20–70 cm long, erect or ascending, angled or slightly ridged below each leaf, reddish brown, the surface often peeling in thin strips with age. Leaves not jointed at the base. Leaf blades 20–70 mm long, 3–15 mm wide, narrowly oblong to narrowly elliptic, rounded to bluntly pointed at the tip, tapered or narrowed at the base, the margins flat or somewhat rolled under at maturity, herbaceous to somewhat leathery in texture, with 3 main veins usually visible toward the base, the surfaces lacking noticeable black dots, lines, or streaks but usually with minute, faint, pale to yellowish brown dots visible, the upper surface green, the undersurface pale green and sometimes somewhat glaucous. Inflorescences appearing as panicles of 7–70 flowers, rounded to more or less flat-topped in outline. Flowers actinomorphic. Sepals 5, all more or less similar in size and shape, 2.5–5.0 mm long, not becoming enlarged at fruiting, lanceolate to broadly ovate, the margins occasionally slightly curled, lacking noticeable yellowish brown or black dots, lines, or streaks. Petals 5, 5–9 mm long, oblanceolate to elliptic, bright yellow, usually shed before fruiting. Stamens 45–85, the filaments not fused into groups. Ovary 1-locular or appearing partially 3-locular by intrusion of the parietal placentae into the locule. Styles 3(4), sometimes fused toward the base, erect and more or less appressed at flowering, persistent and usually separating somewhat as the fruit matures, the stigmas minute. Fruits 4.5–8.0 mm long, ovoid to more or less globose, widest at or slightly below the midpoint, tapered abruptly to the minute beak (this sometimes absent), more or less circular in cross-section. Seeds 4–8 per capsule, 2.0–2.7 mm long, the surface with a coarse network of ridges and pits, dark brown to nearly black. May–September.

Scattered nearly throughout the state (eastern U.S. [but mostly absent from the eastern seaboard] west to Nebraska and Texas; Canada). Glades, ledges and tops of bluffs, openings of mesic to dry upland forests, bottomland and upland prairies, banks of streams and rivers, fens, and margins of ponds and lakes.

Steyermark (1963) and other earlier authors recognized a narrow-leaved variant as var. turgidum, but Adams (1962) and Robson (1996) both believed that leaf variation was more or less continuous within the species. Numerous historical specimens of H. sphaerocarpum in various herbaria were originally misdetermined as H. cistifolium Lam., a taller shrubby species with narrower capsules endemic to the southeastern Coastal Plain. Steyermark (1963) also excluded H. dolabriforme Vent. from the Missouri flora, which had been reported by Fernald (1950) based upon a misdetermined historical specimen of H. sphaerocarpum from southern Missouri. This shrubby species occurs to the east of the state and differs in its loosely ascending stems and unequal sepals.