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Epilobium siskiyouense

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

low willowherb, slender-fruit willowherb, small-fruit willowherb

Habit Herbs ± suffruticose, shoots from woody caudex with barklike periderm extending to 40 cm below ground, shoots with scaly bases. Herbs with numerous small, (3–5 × 2–3 mm), fleshy, sessile turions at or just below ground level, often also with bulblets in proximal to mid cauline leaf axils.
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 or ascending, often clumped, often flushed red, terete, 8–30 cm, simple or branched, glabrous proximal to inflorescence except for elevated strigillose lines decurrent from margins of petiole, strigillose throughout distally.

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, petiole broad, 3–5 mm proximally to subsessile distally;

blade lanceolate or elliptic to narrowly lanceolate distally, 0.8–4 × 0.4–1.3 cm, base attenuate to cuneate, margins subentire to denticulate distally, 5–9 teeth per side, veins 3 or 4 per side, apex obtuse to distally acute, surfaces glabrous with sparsely strigillose margins and abaxial midrib;

bracts reduced and narrower.

Inflorescences

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

nodding to suberect, racemes, 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 2–4 × 1.5–2.5 mm;

pedicel 7–12 mm;

floral tube 1–2 × 1–2 mm, with ring of spreading hairs at mouth inside;

sepals green, narrowly lanceolate, 3–4 × 0.8–1.2 mm;

petals white fading to pink, 4–6.5 × 2.3–4 mm, apical notch 0.8–1.6 mm;

filaments white, those of longer stamens 2.2–3 mm, those of shorter ones 1.2–1.6 mm;

anthers 0.4–0.8 × 0.4–0.6 mm;

ovary 12–18 mm, densely strigillose;

style white, 3.2–4 mm, stigma cream, broadly clavate, 0.6–1.5 × 0.6–1.2 mm, surrounded by at least longer anthers.

Capsules

25–45 mm, surfaces canescent and glandular puberulent;

pedicel 6–25 mm.

often reddish green, 25–55 mm, thin, surfaces sparsely strigillose;

pedicel 15–38 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.

subfusiform, 0.8–1.2 × 0.3–0.4 mm, chalazal collar inconspicuous, 0.02–0.06 mm, light brown, surface papillose;

coma persistent, tawny, 3–6 mm.

2n

= 36.

= 36.

Epilobium siskiyouense

Epilobium leptocarpum

Phenology Flowering Jul–Aug. Flowering Jun–Aug.
Habitat Stream banks, moist, rocky slopes, montane ridges, sometimes on serpentine areas. Boreal/montane moist meadows, stream banks, moist bluffs, sun to part shade, gravelly or sandy soils, mossy ground.
Elevation 1600–2500 m. [5200–8200 ft.] 0–2400 m. [0–7900 ft.]
Distribution
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; ID; MT; OR; 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 leptocarpum often occurs sympatrically with other species of the Alpinae alliance within its Pacific Northwest range, and shares with them the CC chromosomal arrangement. However, it has small compact basal turions and, almost uniquely in Epilobium, bulblets in the leaf axils. The only other species with bulblets is E. fauriei H. Léveillé, an endemic in Japan that has strikingly similar overall morphology to that E. leptocarpum, and shares with it the CC chromosome arrangement.

(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. 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. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
Synonyms E. obcordatum subsp. siskiyouense, E. obcordatum var. laxum E. paddoense
Name authority (Munz) Hoch & P. H. Raven: Madroño 27: 146. (1980) Haussknecht: Monogr. Epilobium, 258, plate 14, fig. 67. (1884)
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