Epilobium siskiyouense
Epilobium suffruticosum
Siskiyou fireweed, Siskiyou rock-fringe, Siskiyou willow-herb
shrubby willowherb
several to many, erect to ascending, loosely clumped, terete, 10–25 cm, rarely branched distal to base, usually short-villous and strigillose throughout, mixed sparsely glandular puberulent distally, rarely subglabrous proximal to inflorescence.
several–many, ascending to erect, terete, 10–25 cm, simple or well-branched, ± densely strigillose.
opposite proximal to inflorescence, alternate and usually crowded distally, sessile;
blade gray-green, narrowly to broadly ovate, 1.3–2.6 × 0.8–2 cm, base rounded to subcordate, margins usually serrulate, 6–12 teeth per side, rarely subentire, veins inconspicuous, 3–5 per side, apex rounded proximally to acute distally, surfaces sparsely short-villous to subglabrous and glaucous;
bracts much reduced.
often crowded, opposite and sometimes with fascicles of very small leaves at proximal nodes, subsessile or attenuate to broad petiole 0.5–1.5 mm, blade light grayish green, narrowly lanceolate to elliptic, 1–2.5 × 0.2–0.7 cm, often exceeding internodes, base cuneate to attenuate, margins entire or ± denticulate, 4–6 low teeth per side, lateral veins inconspicuous, apex blunt proximally to subacute, surfaces ± densely short-strigillose;
bracts not much reduced in size.
erect, compact racemes, densely canescent and glandular puberulent, or subglabrous, only ovaries pubescent.
erect racemes or panicles, ± densely strigillose.
erect;
buds often purplish green, 9–11 × 3.5–5 mm, blunt;
pedicel 6–12 mm;
floral tube 2.1–4 × 2.9–5 mm, prominent ring of tissue 0.3–0.6 mm wide, edged by spreading hairs, 0.9–1.8 mm from base of tube inside;
sepals purplish green, 5–10.5 × 2–3.5 mm, apex acute;
petals pink to rose-purple, obcordate, 10–22.5 × 9.5–15.5 mm, apical notch 2–6.5 mm;
filaments cream, those of longer stamens 6.5–14 mm, those of shorter ones 3.5–11 mm;
anthers cream 1.9–3.3 × 0.7–1.2 mm;
ovary 12–22 mm, ± densely canescent and glandular puberulent;
style white to light pink, 10.5–18 mm, sparsely villous just proximal to stigma, stigma broadly 4-lobed, 1–1.8 × 2.4–4.2 mm, exserted beyond anthers.
slightly nodding;
buds 4–8 × 1.5–3.5 mm, apiculate;
floral tube funnelform to obconic, 1.8–3 × 1.9–2.6 mm, ring of spreading hairs 1–2.5 mm from base inside;
sepals 3–6.5 × 1–2.6 mm, often apiculate, abaxial surface densely strigillose;
petals cream to light yellow, obcordate, 5–9.3 × 2–3.8 mm, slightly unequal with upper 2 longer, apical notch 1–2.3 mm;
filaments cream, slightly inflated at base, those of longer stamens 6–10 mm, those of shorter ones 4.5–8 mm;
anthers cream-yellow, 1.4–2.2 × 0.6–1.1 mm;
ovary 4–9 mm, densely white-canescent;
style declined below main plane of flower, cream, 7.8–14.5 mm, glabrous, stigma deeply 4-lobed, 0.8–1.2 × 1.8–2.8 mm, lobes spreading-recurved 0.9–1.2 mm, exserted beyond longer anthers, often prematurely exserted and protogynous.
25–45 mm, surfaces canescent and glandular puberulent;
pedicel 6–25 mm.
often curved, fusiform-clavate, 10–30 mm, surfaces finely strigillose;
pedicel 4.5–13 mm.
narrowly obovoid, 1.4–1.9 × 0.6–0.7 mm, with low, obscure chalazal collar, light brown, surface papillose;
coma easily detached, somewhat tawny, 4–8 mm.
narrowly obovoid to oblanceoloid, with constriction 0.7–1.3 mm from micropylar end, 2.1–3 × 0.7–1.1 mm, very inconspicuous chalazal collar, light brown, surface low-papillose;
coma easily detached, tawny, 7–9.5 mm, with unusually dense hairs.
= 36.
= 30.
Epilobium siskiyouense
Epilobium suffruticosum
Epilobium siskiyouense is endemic to the Klamath region in southwestern Oregon (Jackson County) and north-central California in the Salmon, Scott Bar, and Siskiyou mountains of Siskiyou and Trinity counties. As noted by Hoch and Raven, this geographical range and several morphological features appear to be intermediate between those of E. obcordatum and E. rigidum. All three species have unusually large flowers (12–26 mm) with four-lobed stigmas, and as a group are quite distinct from their congeners in the region. Despite these similarities, the three taxa differ substantially in details of floral structure, especially regarding the dimensions of the floral tube. Specifically, E. rigidum has mean petal length 18.2 mm, floral tubes 1–1.6 × 2.5–3.6 mm; E. siskiyouense mean petal length 17.1 mm, floral tubes 2.1–4 × 2.9–5 mm; and E. obcordatum mean petal length 18.6 mm, floral tubes 3.2–5.2 × 2.2–3.6 mm. Thus, in flowers that are similar in overall size and aspect, E. rigidum has a very short, broad floral tube, E. obcordatum has a relatively long, narrow tube, and E. siskiyouense has a tube intermediate in size and shape. In terms of the ratio of tube length to width, the three taxa do not overlap. Although these characters are difficult to include in a key (since they require floral dissection and/or precise measurements), they are diagnostic for these species.
Epilobium siskiyouense has an additional diagnostic floral character that is unique in the genus. Whereas most other species of Epilobium have a simple ring of spreading hairs, sometimes with a low ridge of tissue near the mouth of the floral tube, E. siskiyouense has a relatively broad ring of tissue (0.3–0.6 mm wide), shaped like a washer, from which spreading hairs arise; this feature may provide protection for the nectar.
Epilobium siskiyouense has two distinct patterns of vestiture on the stems. In some specimens, the lower stems are mixed canescent and glandular puberulent and the inflorescence only glandular puberulent. In other specimens, the stems are subglabrous below a sparsely canescent and glandular puberulent inflorescence. There is no obvious correlation of this difference with any other morphological, ecological, or geographical factors.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Epilobium suffruticosum shares its unusual cream-yellow flower color only with E. luteum, a distantly related species in sect. Epilobium. Both species have relatively large flowers with 4-lobed stigmas and are visited quite intensively by bees and other insect pollinators. Nevertheless, these species differ dramatically in habit, leaves, seeds, and many other characters, do not overlap at all in distribution, and are never confused with one another; the similar floral features must have been derived independently.
The flowers of Epilobium suffruticosum are also slightly zygomorphic, which is relatively rare in the genus. In the field and on many herbarium specimens of E. suffruticosum, the stigmas are clearly exserted even before the flowers are fully open. The label for Raven 26451 (Wyoming, Park County, MO) notes: “protogynous; in late bloom, most flowers male-sterile.” Several flowers from this collection have undeveloped anthers, suggesting that the flowers are functionally pistillate. However, these plants are not sterile since they have apparently fertile capsules with fully developed seeds.
The distribution of Epilobium suffruticosum consists of two clusters of fairly common occurrence—in northwestern Wyoming around Yellowstone and Teton national parks, and in south-central Idaho mainly in the drainages of the Boise and Payette rivers—with more scattered collections in western Montana north to Flathead County, and a single collection to the south in Weber County, northern Utah. There are no obvious morphological discontinuities among these specimens, nor any obvious explanation for the gaps in distribution; it may be due to collecting bias. This species is commonly found on gravel/sand bars of cold montane streams and rivers, in a stable association despite the apparent ephemeral nature of these habitats. It would appear that the plants have deep, woody roots by which they anchor themselves; in the spring flood stages of these rivers, they must experience complete inundation and considerable scouring, yet persist, often in moderately large colonies.
The exact locality of the type collection (streams east of Wallawallah, plains of the Upper Columbia River, Oregon) is problematic, since the closest known localities are at least 250 km southeast of the town of Walla Walla, Washington. Whether this is a matter of the historical accuracy of the locality by Nuttall or of the local extinction of this species from a locality in eastern Oregon cannot be determined at present. A collection by Hayden in 1859 (Powder River, Wyoming) is far outside the range of E. suffruticosum and may have been mislabeled.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
OR
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
