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FNA | Family List | FNA Vol. 6 | Hypericaceae | Triadenum

2. Triadenum fraseri (Spach) Gleason, Phytologia. 2: 289. 1947.
[E F]

Millepertuis de Fraser Millepertuis de Fraser

Elodes fraseri Spach, Ann. Sci. Nat., Bot., sér. 2, 5: 168. 1836 (as Elodea); Hypericum virginicum Linnaeus var. fraseri (Spach) Fernald; Triadenum virginicum (Linnaeus) Rafinesque subsp. fraseri (Spach) J. M. Gillett; T. virginicum var. fraseri (Spach) Cooperrider

Herbs erect, 1.5–7.5 dm, sometimes with ascending branches in distal 1/2+. Stems shallowly 4-lined at first, then terete. Leaves sessile, <sometimes amplexicaul>; blade broadly ovate or triangular-ovate to oblong, 15–50(–70) × 10–40(–50) mm, base usually ± shallowly cordate, rarely truncate, apex rounded to retuse, gland dots laminar (relatively dense) and intramarginal.

Flowering late summer–early fall (Jul–Sep). Wooded swamps, fens, marshes, lakeshores, organic to silty and sandy substrates, along shores, beaver meadows, poor fens (rarely in true bogs); 0–500 m; St. Pierre and Miquelon; B.C., Man., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Sask.; Conn., Del., Ill., Ind., Iowa, Maine, Md., Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Tenn., Vt., Va., W.Va., Wis.

Inflorescences spiciform-cylindric to pyramidal, 1–10-flowered from distal 1–2 nodes, sometimes with subsidiary inflorescences from to 4 proximal nodes and flowering branches from to 4 further nodes. Flowers 8–10 mm diam.; sepals oblong to elliptic-oblong, 2.5–5 × 1–1.5 mm, apex usually obtuse to rounded, rarely acute; petals oblong-obovate to oblanceolate, 5–8 mm; stamen fascicles 3 mm; filaments 1/2 connate; styles 0.5–1.5 mm. Capsules cylindric to ovoid-ellipsoid, 7.5–9 × 3.5–4.5 mm, apex subacute to obtuse. Seeds 0.5–11.2 mm. 2n = 38.

According to B. Boivin (1967), Triadenum fraseri (as Hypericum virginicum) was introduced into British Columbia from eastern Canada in peat. It seems to be almost always distinguishable from T. virginicum and to have a distinct habitat; it merits specific rank.


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