Triadenum
Hypericaceae
marsh, marsh St. John's wort
St. John's wort family
internodes with 2 or 4 raised lines at first, then terete (not lined).
sessile, subsessile, or petiolate;
blade relatively broad, venation pinnate, tertiary veins densely reticulate, glands punctiform, pale (records of black gland dots are probably all due to fungal attack), intramarginal and laminar.
opposite [alternate or whorled], simple, estipulate, sessile, subsessile, pseudopetiolate, or petiolate;
blade with pellucid glands and/or canals containing essential oils, margins entire [rarely gland-fringed], surfaces with black, reddish, or amber glands containing hypericin and pseudohypericin.
terminal, sometimes also axillary, cymose, 2–15-flowered, or solitary flower, branching dichasial;
bracts and bracteoles relatively small.
terminal or axillary, cymose [thyrsoid] or solitary flowers.
tubular or campanulate at first, expanding to stellate for short time each day;
sepals persistent, 5, distinct or almost so, margins not glandular-ciliate;
petals deciduous, 5, partly imbricate or contorted, pink or flesh-colored, sometimes green-tinged;
stamens persistent, 9, in 3 fascicles, each with 3 stamens;
filaments of each fascicle 1/5–1/2+ connate;
anthers yellow, isodiametric to oblate or shortly oblong, with amber gland on connective;
staminode fascicles 3, alternating with stamen fascicles;
ovary 3-merous;
placentation axile;
ovules relatively numerous on each placenta;
styles distinct, spreading.
homostylous [heterostylous];
sepals persistent or deciduous, (3–)4–5, glanduliferous like leaves;
petals persistent or deciduous, 3–5[–6], distinct, imbricate or contorted [decussate], orange, pink, or yellow, [white, red], sometimes green- or red-tinged, [sometimes with adaxial scale], glanduliferous;
stamens persistent or deciduous, in 2 whorls, sometimes in fascicles, sometimes reduced to staminodes;
filaments distinct or ± connate;
anthers 2-locular, dehiscing longitudinally;
ovary superior, 2–5-merous;
placentation axile to parietal;
ovules 1–2+ on each placenta, anatropous;
styles 2–5, distinct or basally [to completely] connate, elongate;
stigmas minute or ± expanded.
capsular [baccate], dehiscence septicidal from apex [loculicidal].
3-valved, with glandular vittae.
narrowly cylindric, carinate;
testa reticulate-foveolate.
sometimes carinate [winged or carunculate];
endosperm absent;
embryo straight [curved];
cotyledons 25–40% of total embryo length.
= 19.
Triadenum
Hypericaceae
Nomenclatural complexities and confusions associated with Triadenum were reviewed by N. K. B. Robson (1977). B. R. Ruhfel et al. (2011) concluded from molecular studies that Triadenum is part of Hypericum. Robson (2012) gave reasons why Triadenum is generically distinct.
Species 6 (4 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 9, species 700+ (2 genera, 58 species in the flora).
Hypericaceae flowers are always bisexual, the anther and all or part of the filament remain distinct, the cotyledons are distinct and usually 25–40% of the length of the embryo, and specialization has resulted in heterostyly. In the Calophyllaceae, the anthers and filament are distinct, the cotyledons usually form most of the embryo and may be completely connate, and specialization has resulted in dioecism. In the Clusiaceae, which are also largely dioecious, distinct anthers are often lacking, the stamens having become more or less connate in masses around the ovary, and the cotyledons are minute or absent.
The dark red compounds hypericin and pseudohypericin, naphtho-dianthrone derivatives that are widespread in the Hypericaceae, are contained within black or red gland-dots or -lines in various parts of the plant. These compounds are photosensitizing and lead to eruptions on muzzles of grazing animals. This phenomenon is especially troublesome in dry regions where
alternative fodder may be scarce, for example, California, Iraq, Australia, and South Africa. Hypericum perforatum, which is native in Iraq and introduced in the other three regions, is the main source of trouble. Reports from Ontario indicate that field workers have experienced severe reaction over prolonged exposure to H. perforatum. Hypericum perforatum is also used privately (but not prescribed) as source of an antidepressant; the relevant active ingredients for this treatment are unknown (S. L. Crockett 2003).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves petiolate. | T. walteri |
1. Leaves sessile or (distal) subsessile | → 2 |
2. Leaves: gland dots intramarginal. | T. tubulosum |
2. Leaves: gland dots laminar and intramarginal | → 3 |
3. Sepals 4–7(–8) mm, apex acute to acuminate; styles 2–3.5 mm. | T. virginicum |
3. Sepals 2.5–5 mm, apex usually obtuse to rounded, rarely acute; styles 0.5–1.5 mm. | T. fraseri |
1. Herbs, subshrubs, or shrubs; petals yellow to orange, sometimes red-tinged; stamens (5–)10–300(–650), in continuous or interrupted ring or in (3–)4–5 fascicles; filaments distinct or basally connate, staminode fascicles 0. | Hypericum |
1. Herbs; petals pink or flesh-colored, sometimes green-tinged; stamens 9, in 3 fascicles; filaments 1/5–1/2+ connate, staminode fascicles 3, alternating with stamen fascicles. | Triadenum |
WA
USDA Plants Database- Local floras:
CA, 
OR - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
