1. Triadenum tubulosum (Walter) Gleason

Hypericum tubulosum Walter

Pl. 362 i, j; Map 1575

Stems 45–100 cm long. Leaves sessile (uppermost) to short-petiolate (lowermost). Leaf blades 4–15 cm long, oblong-elliptic or oblong-ovate to elliptic-oblanceolate, the tip rounded to bluntly pointed, the base broadly rounded to cordate in most or only the uppermost leaves, narrowed or tapered in the lowermost leaves (sometimes all of the leaves in juvenile plants), the upper surface green to olive green, the undersurface pale green, sometimes somewhat glaucous, lacking glandular dots. Sepals 4–6 mm long, oblong to oblong-lanceolate, usually sharply pointed at the tip. Petals 5–8 mm long. Stamens in each group with the filaments united to at or above the midpoint. Fruits 9–11 mm long. August–September.

Uncommon in the Mississippi Lowlands Division (eastern [mostly southeastern] U.S. west to Illinois, Oklahoma, and Texas). Swamps and bottomland forests.

In Missouri, T. tubulosum is much less common than the closely related T. walteri. The two taxa sometimes have been treated as varieties of T. tubulosum (Fernald, 1950; Cooperrider, 1989). Records of T. tubulosum from the Ozark and Ozark Border Divisions (and some of those from the Mississippi Lowlands) have been found to represent misdetermined specimens of T. walteri and usually include immature plants lacking leaves with cordate bases, which tend to develop only later in the season. Steyermark (1963) corrected earlier reports of the closely related T. virginicum (L.) Raf. from southeastern Missouri, which were based on misdetermined specimens of T. tubulosum. Triadenum virginicum has leaves similar in shape to those of T. tubulosum, but with the undersurface having resinous punctations, as in T. walteri, as well as slightly larger flowers than in either of the Missouri species.