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Epilobium siskiyouense

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

largeflower spike-primrose, pale boisduvalia

Habit Herbs ± suffruticose, shoots from woody caudex with barklike periderm extending to 40 cm below ground, shoots with scaly bases. Herbs with taproot.
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.

terete, 4.5–55 cm, simple or with proximal ascending branches and/or distal branches, ± densely villous and/or strigillose, mixed glandular puberulent distally or glabrescent.

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 only in proximal pairs, alternate and crowded distally, subsessile, blade narrowly elliptic or lanceolate, 1.2–5 × 0.2–1.2 cm, usually longer than internodes, base cuneate to attenuate, margins subentire or sparsely serrulate, 3–5 teeth per side, veins inconspicuous, 2–7 per side, apex acute, surfaces villous;

bracts same size and shape as leaves.

Inflorescences

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

erect spikes, often congested proximally, sometimes nodding in bud, simple, or sometimes sparsely branched, ± densely mixed villous, strigillose, and glandular puberulent.

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, mostly chasmogamous, sometimes initiating at second or third proximal node;

buds 3–5 × 2.5–3.5 mm, apex blunt;

floral tube 1.5–3 × 1.1–2.8 mm, ring of lax hairs near base inside;

sepals erect, (1.5–)2–6.2 × (0.5–)1–2.2 mm, densely villous and glandular pubescent abaxially;

petals rose-purple, (2.8–)4.2–9.8 × (2.2–)3.5–5.3 mm, apical notch 1.2–3.5 mm;

filaments rose-purple, those of longer stamens 2.4–6.5 mm, those of shorter ones 0.9–4.3 mm;

anthers 0.6–1.6 × 0.2–0.8 mm;

ovary 3.5–9 mm, densely pubescent;

style pink, 3.3–9.2 mm, stigma 4-lobed, ± subentire in smaller flowers, 0.7–1.4 × 0.5–1.3 mm, usually surrounded by, rarely exserted beyond, longer anthers.

Capsules

25–45 mm, surfaces canescent and glandular puberulent;

pedicel 6–25 mm.

narrowly fusiform, (10–)14–21 × 1–2.1 mm, beak 2–5 mm, ribs usually broad and prominent, septa and central column disintegrating with age, surfaces ± densely villous;

subsessile.

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.

8–12 per capsule, initially in 4 locules, at maturity pushed into 2 rows proximally, 1 overlapping row distally, irregularly angular-fusiform, 1.8–2.3x 0.7–0.9 mm, chalazal collar absent, surface irregularly reticulate.

2n

= 36.

= 20.

Epilobium siskiyouense

Epilobium pallidum

Phenology Flowering Jul–Aug. Flowering May–Aug(–Sep).
Habitat Stream banks, moist, rocky slopes, montane ridges, sometimes on serpentine areas. Stream banks and washes in vernally moist areas in shrubland or lower forested regions.
Elevation 1600–2500 m. [5200–8200 ft.] 60–2100 m. [200–6900 ft.]
Distribution
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; OR
[WildflowerSearch map]
[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.)

P. H. Raven and D. M. Moore (1965) observed that smaller-flowered individuals of this species were sometimes difficult to separate from Epilobium torreyi (reported as Boisduvalia stricta), especially in the absence of mature fruits. The capsules of E. pallidum are usually longer and thinner than those of related species and the internal structure is highly distinctive. The stigmas of larger-flowered plants often are exserted beyond the anthers, increasing the chances for outcrossing.

(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. Pachydium
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. mirabile, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, 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 Boisduvalia pallida, B. macrantha
Name authority (Munz) Hoch & P. H. Raven: Madroño 27: 146. (1980) (Eastwood) Hoch & P. H. Raven: Phytologia 73: 458. (1993)
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