Flora of North America species comparison

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Epilobium siskiyouense

Epilobium mirabile
Epilobium siskiyouense

Siskiyou fireweed, Siskiyou rock-fringe, Siskiyou willow-herb

hairy-stem willowherb, Olympic Mountain willowherb
Habit Herbs ± suffruticose, shoots from woody caudex with barklike periderm extending to 40 cm below ground, shoots with scaly bases. Herbs with sessile, compact, fleshy turions that leave dark basal scales.
Stems

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.

erect, loosely or not clumped, terete, 7–30 cm, usually simple, rarely branched, subglabrous with raised strigillose lines decurrent from margins of petioles, or densely strigillose and without raised lines.
Leaves

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.

opposite proximal to inflorescence, alternate distally, petioles 1–3 mm proximally, subsessile distally;

blade ovate to narrowly ovate, coriaceous, 1.5–3 × 0.7–1.2 cm, base rounded to cuneate, margins denticulate, 8–12 teeth per side, veins indistinct, 4–9 per side, apex obtuse proximally to acute distally, surfaces sparsely strigillose, mainly on margins and midrib;

bracts not much reduced.
Inflorescences

erect, compact racemes, densely canescent and glandular puberulent, or subglabrous, only ovaries pubescent.

erect racemes, rarely branched, densely strigillose.
Flowers

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.

erect;

buds 3–4 × 1.5–2.2 mm;

pedicel 4–5 mm;

floral tube 1.5–2 × 1.6–2.2 mm, sparsely glandular puberulent, sometimes mixed strigillose;

sepals often purplish red, 2–3.2 ×1.5–2.4 mm;

petals white, often red-tinged at apex, 3.8–5 × 2–3 mm, apical notch 0.4–0.8 mm;

filaments cream, those of longer stamens 1.4–2.3 mm, those of shorter ones 0.8–1.4 mm;

anthers 0.4–0.6 × 0.3–0.5 mm;

ovary 10–18 mm, densely strigillose and glandular puberulent;

style yellow or light pink, 2–2.3 mm, stigma broadly clavate, 0.8–1 × 0.6–0.7 mm, surrounded by longer anthers.
Capsules

25–45 mm, surfaces canescent and glandular puberulent;

pedicel 6–25 mm.

30–45 mm, relatively thick (2–3 mm), surfaces ± sparsely glandular puberulent and mixed strigillose;

pedicel 5–16 mm.
Seeds

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, 1.7–2.2 × 0.6–0.8 mm, chalazal collar inconspicuous, gray to light brown, surface low papillose or reticulate;

coma readily detached, white, very full, 10–15 mm.
2n

= 36.

= 36.

Epilobium siskiyouense

Epilobium mirabile
Phenology Flowering Jul–Aug. Flowering Jul–Aug.
Habitat Stream banks, moist, rocky slopes, montane ridges, sometimes on serpentine areas. Subalpine scree slopes, gravelly tussock meadows.
Elevation 1600–2500 m. [5200–8200 ft.] 1500–2600 m. [4900–8500 ft.]
Distribution
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
MT; WA; AB; BC
[BONAP county map]
Discussion

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 mirabile also has the CC chromosomal arrangement and is one of the least common species of Epilobium in North America; fewer than 20 collections are known, even though its range is quite large. Most collections are from the Olympic Peninsula in Washington or Waterton-Glacier International Peace Park in Alberta and adjacent Montana. However, one collection is known from Powell County in central Montana, and one from Manning Provincial Park in British Columbia. The species may be more widespread but under-collected due to its restricted habitat, mainly on subalpine south-facing scree slopes.

Specimens of Epilobium mirabile from the northern Rocky Mountains (Alberta and Montana) have subglabrous stems with strong, raised, strigillose lines and seeds with low papillose surfaces, whereas specimens from the northern Cascades (British Columbia) and Olympic Mountains (Washington) have densely strigillose stems with no raised lines and seeds with reticulate surfaces. The plants otherwise have very similar and distinctive morphology and ecology.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Epilobium Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Epilobium
Sibling taxa
E. anagallidifolium, E. arcticum, E. brachycarpum, E. campestre, E. canum, E. ciliatum, E. clavatum, E. cleistogamum, E. coloratum, E. davuricum, E. densiflorum, E. densum, E. foliosum, E. glaberrimum, E. hallianum, E. hirsutum, E. hornemannii, E. howellii, E. lactiflorum, E. leptocarpum, E. leptophyllum, E. luteum, E. minutum, E. mirabile, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, E. pallidum, E. palustre, E. parviflorum, E. rigidum, E. saximontanum, E. septentrionale, E. smithii, E. suffruticosum, E. torreyi
E. anagallidifolium, E. arcticum, E. brachycarpum, E. campestre, E. canum, E. ciliatum, E. clavatum, E. cleistogamum, E. coloratum, E. davuricum, E. densiflorum, E. densum, E. foliosum, E. glaberrimum, E. hallianum, E. hirsutum, E. hornemannii, E. howellii, E. lactiflorum, E. leptocarpum, E. leptophyllum, E. luteum, E. minutum, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, E. pallidum, E. palustre, E. parviflorum, E. rigidum, E. saximontanum, E. septentrionale, E. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
Synonyms E. obcordatum subsp. siskiyouense, E. obcordatum var. laxum
Name authority (Munz) Hoch & P. H. Raven: Madroño 27: 146. (1980) Trelease: Contr. U.S. Natl. Herb. 11: 404. (1906)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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