Chamaenerion
Chamaenerion latifolium
fireweed, rosebay willowherb
alpine fireweed, broad-leaf fireweed, broad-leaf willowherb, dwarf fireweed, river-beauty, épilobe à feuilles larges
erect, usually unbranched, rarely sparsely branched, strigillose or glabrous.
usually clumped, terete, unbranched or scarcely branched, 12–35 cm, glabrous proximally, subglabrous or sparsely to, rarely, densely strigillose distally.
cauline, usually alternate, rarely subopposite or subverticillate in proximal pairs;
subsessile;
blades scalelike and minute below ground, proximal blades small, coriaceous to submembranous, triangular-ovate to lanceolate, distal blades usually linear to lanceolate or elliptic, rarely ovate, often subcoriaceous.
petiole 0–2 mm;
basal blades often brown, triangular-ovate, 0.7–1 cm;
cauline blades elliptic or ovate to lanceolate-elliptic, 2–5(–8) × 0.6–1.7(–2) cm, base cuneate to subobtuse, margins subentire or remotely punctate-denticulate (with 4–7 teeth), apex obtuse or acuminate, lateral veins obscure, 3 or 4 on each side of midrib, submarginal vein absent, surfaces subglabrous or strigillose;
bracts ca. 1/2 as long as blades.
terminal, racemes [spikes], erect or suberect.
erect racemes, sparsely to densely strigillose.
bisexual, protandrous, slightly zygomorphic, opening on axis nearly perpendicular to stem axis, deciduous from ovary apex;
floral tube absent;
sepals green or reddish green, spreading;
petals spreading, usually rose purple to pink, rarely white, margins entire;
stamens subequal;
filament bases slightly bulged proximally to form a chamber around nectary disc, initially erect, later deflexed;
anthers versatile, pollen bluish gray [yellow], shed in monads, 3(–5)-aperturate;
ovary 4-locular, nectary disc raised on ovary apex;
style initially deflexed, becoming erect 2–3 days after onset of anthesis, stigma deeply 4-lobed, lobes spreading open to revolute as style becomes erect, commissural, receptive only on inner surfaces, surface dry, with multicellular papillae.
erect in bud, nodding at anthesis, opening laterally;
buds oblong-obovoid, 8–17 × 3–6 mm;
sepals often flushed purplish red, oblong-lanceolate, 10–16 × 1.5–3.5 mm, base attenuate or ± short-clawed, apex acute, usually subglabrous;
petals rose purple to pink, obovate or oblong-obovate, 10–24(–32) × 7–15(–21) mm, sometimes slightly unequal, lower pair slightly shorter and narrower, apex rounded or retuse;
filaments white or pink, 6–11 mm;
anthers dark red, oblong or elliptic-oblong, 1.2–4 × 0.7–1.5 mm;
ovary often flushed purplish red, 1.5–3 cm, usually gray-canescent;
nectary disc raised 0.5–1 mm on ovary apex, 3–4 mm diam., glabrous;
style light pink to rose purple, 3.5–8 mm, glabrous;
stigma lobes 2–3.5 mm, recurved at maturity, surface white, papillose.
a capsule, loculicidal, spreading to erect, narrowly cylindrical, terete to quadrangular, splitting to base with intact central column;
pedicellate.
2.5–8 cm, strigillose-canescent;
pedicels 1.2–2.5 cm.
200–500, in 1 row per locule, gray-brown, narrowly clavate, with ± persistent coma at chalazal end.
fusiform, 1.2–2.1 × 0.4–0.6 mm, acuminate at micropylar end, chalazal collar 0.1–0.2 mm, surface irregularly low-reticulate;
coma tawny or dingy white, 9–15 mm, not readily deciduous.
= 36, 72.
Chamaenerion
Chamaenerion latifolium
Species 8 (2 in the flora).
J. Holub (1972b) argued that the correct name for this group, when segregated from Epilobium, should be Chamerion (Rafinesque) Rafinesque ex Holub. However, A. N. Sennikov (2011), using the more recent and clarified ICBN (Melbourne Code), correctly argued that the name of the segregated genus should be Chamaenerion, and that opinion is followed here.
All species of Chamaenerion tested to date have been self-compatible, although the strong protandry can result in low fertilization rates if there is a shortage of pollinators. Flowering is diurnal, with each flower generally remaining open for three to five or more days.
All eight species (nine taxa) of Chamaenerion are restricted to the northern hemisphere, and six of eight species occur only in Eurasia; Circaea is the only other genus of Onagraceae in which most species occur outside of the western hemisphere (D. E. Boufford 1982b). Chamaenerion is generally divided into two sections, each with four species (T. Tacik 1959; and, as Chamerion, J. Holub 1972b; W. L. Wagner et al. 2007). P. H. Raven (1976) and most others who treated this group as a section of Epilobium divided it into two corresponding subsections. Both species of Chamaenerion in North America are placed in sect. Chamaenerion (not treated formerly here), along with two species endemic to the Himalayan region, C. conspersum (Haussknecht) Kitamura and C. speciosum (Decaisne) Hoch & Gandhi (Chen C. J. et al. 1992); the other four species, all endemic in Eurasia, comprise sect. Rosmarinifolium Tacik.
Chamaenerion differs from Epilobium in leaves nearly always alternate, rarely subopposite or verticillate near stem base (versus opposite at least on proximal stem); absence of a floral tube (versus a distinct floral tube); slightly zygomorphic flowers with subequal stamens that are erect, later deflexed, and a style that is deflexed, later erect (versus actinomorphic flowers with erect stamens in two unequal series and erect style); and pollen shed in monads (versus pollen shed in tetrads, or monads in one species). Molecular analyses (D. A. Baum et al. 1994; R. A. Levin et al. 2004) provided strong support for Chamaenerion as a monophyletic group separate from Epilobium, and for sect. Chamaenerion (only C. angustifolium and C. latifolium sampled) as monophyletic.
The superfluous and illegitimate name Pyrogennema Lunell pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Chamaenerion latifolium is a widespread arctic-alpine species found abundantly across arctic Alaska, Canada, and Greenland, as well as in comparable arctic regions in Eurasia. It also occurs farther south along the cordilleras at high alpine elevations (to 4500 meters) (Chen C. J. et al. 1992; P. C. Hoch 2012 [as Chamerion]).
Both diploid (n = 18) and tetraploid (n = 36) plants of Chamaenerion latifolium have been documented, but variation in ploidy shows no obvious association with any morphological features, except that diploids have mostly three-pored pollen and tetraploids a larger proportion of four-pored grains (E. Small 1968). Using a few meiotic counts and pollen pore number on herbarium specimens, Small found diploids in Alaska and western North America, and tetraploids in eastern Canada, Greenland, and Iceland, but the ranges overlap (T. Mosquin and E. Small 1971). The lack of correlation of geography with any other variable characters led Small to oppose any infraspecific classification, a decision followed in this treatment. The mechanism of polyploidization is probably autopolyploidy, based in part on the high rate of quadrivalent formation in tetraploid meiosis (Small).
In 1813, M. Wormskjöld described Epilobium intermedium Wormskjöld [recombined variously as Chamaenerion angustifolium var. intermedium (Wormskjöld) Lange; E. angustifolium var. intermedium (Wormskjöld) Fernald; and Chamerion angustifolium subsp. intermedium (Wormskjöld) Á. Löve] from Greenland, noting that it was intermediate between E. angustifolium and E. latifolium. From the description by Wormskjöld, it is not clear whether his plant was actually a hybrid, or simply an unusual variant of one or the other species. Hybrids between these two species have been reported in transitional habitats (T. W. Böcher 1962), but they are surprisingly infrequent, given the huge region of sympatric occurrence (T. Mosquin and E. Small 1971).
White-petaled individuals or populations occur at low frequency and have sometimes been given taxonomic status, but flower color differences do not correlate with other morphological or geographical variation.
Chamaenerion halimifolium Salisbury is illegitimate and pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blades elliptic or ovate to lanceolate-elliptic, 2–5(–8) × 0.6–1.7(–2) cm, without submarginal vein, petioles 0–2 mm; bracts ca. 1/2 as long as cauline leaves; seeds fusiform, 1.2–2.1 × 0.4–0.6 mm, with distinct chalazal collar (0.1–0.2 mm); styles glabrous, shorter than stamens. | C. latifolium |
1. Leaf blades lanceolate to linear, proximally oblong to obovate, (3–)5–23 × 0.3–3.4 cm, with ± prominent submarginal vein, petioles 0–7 mm; bracts much smaller than cauline leaves; seeds narrowly obovoid to oblong, 0.9–1.3 × 0.3–0.4 mm, with inconspicuous chalazal collar (to 0.1 mm); styles pubescent proximally, longer than stamens. | C. angustifolium |
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