Hypericum majus
Hypericum gymnanthum
greater Canada St. John's-wort, greater Canadian St. John's-wort, large Canadian St. John's-wort, large St. John's wort, millepertuis majeur
claspingleaf St. Johnswort, small-flower St. John's wort
internodes 4-angled.
internodes 4-angled.
spreading, sessile or distal subamplexicaul;
blade lanceolate to narrowly oblong-elliptic or (proximal) oblanceolate, 10–45 × (2–)6–12 mm, papery to membranous, margins plane, apex acute to rounded, basal or near-basal veins (3–)5–7, midrib with to 4 pairs of branches.
spreading, sessile or amplexicaul;
blade usually ovate-triangular to broadly ovate, rarely oblong (mid and distal blades lanceolate-deltate), 5–25 × 3–12 mm, papery to membranous, margins plane, apex usually subacute, basal veins (3–)5, midrib usually with 1–2 pairs of branches.
corymbiform to cylindric, 3–30-flowered, usually compact, branching mostly dichasial.
laxly corymbiform to cylindric, (1–)5–65-flowered, branching mostly dichasial.
6–7 mm diam.;
sepals lanceolate to narrowly elliptic, equal, 3.5–6.5 × 0.8–1.5 mm, margins sometimes ciliate, not setulose-ciliate, apex acute;
petals golden yellow, sometimes red-veined, oblanceolate, 3.5–6 mm;
stamens 12–21, obscurely 5-fascicled;
styles 0.6–1 mm;
stigmas broadly capitate.
4.5–7 mm diam.;
sepals lanceolate to narrowly ovate, equal, 3–5 × 0.8–1.2 mm, margins sometimes ciliate, not setulose-ciliate, apex acute to acuminate;
petals bright yellow, oblanceolate, 2–4 mm;
stamens 10–14, scarcely grouped;
styles 0.5–0.7 mm;
stigmas broadly capitate.
narrowly conic-ellipsoid, 4–8 × 2.5–3.5 mm, broadest proximal to middle.
narrowly conic-ellipsoid, 3–5 × 1.5–2 mm, usually broadest at or near middle.
0.5–0.7 mm;
testa finely linear-scalariform.
0.5–0.6 mm;
testa finely linear-scalariform.
= 16.
= 16.
Hypericum majus
Hypericum gymnanthum
Hypericum majus was the western member of a vicariant species pair, differing from the originally eastern member (H. canadense) by the broader leaves, usually more-congested inflorescence, and larger flowers. These species became sympatric in glaciated northeastern North America and now hybridize freely, notably in Wisconsin (F. H. Utech and H. H. Iltis 1970). Hybrids are intermediate in form between the parents and have also been recorded from Connecticut, Massachusetts, and New Hampshire. Hypericum majus hybridizes also with H. mutilum, with subsp. mutilum in Maine, and with subsp. boreale in Michigan and Wisconsin.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Hypericum gymnanthum was introduced into Poland; it is now extinct there. It is closely related to H. mutilum; it differs from that species in the broader, usually deltate leaves; fewer, stricter branches; no condensed apical stem internode; and larger flowers with lanceolate to ovate sepals.
Hybrids of Hypericum gymnanthum with H. mutilum have been reported from Maryland, Mississippi, North Carolina, Tennessee, and West Virginia, and, perhaps erroneously, with H. canadense from Virginia.
Hypericum gymnanthum has clearly been introduced (recently?) into the Azores, not necessarily by man. Seeds may well have been carried there by birds.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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