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glandular willowherb, Rocky Mountain willowherb, Rocky Mountain willowweed, épilobe des rocheuses

dense boisduvalia, dense spike-primrose, dense willowherb, dense-flower spikeprimrose, dense-flower willowherb, willow herb

Habit Herbs usually with sessile, fleshy, underground turions, or sometimes thick, elongated shoots with dark, decussate scales. Herbs usually with taproot, sometimes with loose network of roots.
Stems

erect, strict, terete, 4–55 cm, simple or well branched in age, subglabrous proximally to mixed strigillose and glandular puberulent distally, with raised strigillose lines decurrent from margins of petioles.

erect or ascending, terete, 4–150 cm, simple or branched with strong central axis, proximal branches ascending or suberect, villous or strigillose, often mixed glandular puberulent distally.

Leaves

opposite proximal to inflorescence, alternate and reduced distally, often ± appressed, usually subsessile, rarely petiole 1–3 mm, often clasping;

blade obovate proximally to ovate, lanceolate, or narrowly elliptic distally, 1–5.5(–6.5) × 0.4–2(–2.4) cm, base rounded or obtuse, margins low denticulate, 9–30 teeth per side, veins ± conspicuous, 3–6 per side, apex subacute, surfaces subglabrous with strigillose margins;

bracts much reduced.

opposite and often early-deciduous proximally, alternate and crowded distally, usually subsessile, rarely petiole 1–2 mm, blade usually narrowly lanceolate to sublinear, rarely to lanceolate, 1.4–7.5(–9.2) × 0.5–1.4 cm, base cuneate to attenuate, margins remotely to sharply serrulate, 5–12 teeth per side, lateral veins obscure, 2–5 per side, apex acute, surfaces densely villous and/or strigillose;

bracts broader than cauline leaves, broadly lanceolate to ovate or subrotund, 0.5–2.5 × 0.3–1.8 cm, long-acuminate, sometimes folded on midrib.

Inflorescences

erect, sometimes nodding in bud, racemes, sometimes sparsely branched.

erect spikes, congested, simple, densely villous and strigillose, sometimes mixed glandular puberulent.

Flowers

erect;

buds 2–3.5 × 1.8–2.5 mm;

pedicel 0–1 mm;

floral tube 0.8–1.4 × 0.8–1.9 mm, ring of sparse spreading hairs at mouth inside;

sepals sometimes flushed red, 1.2–3.5 × 0.6–1.4 mm, abaxial surface strigillose and sometimes mixed glandular puberulent;

petals usually white, infrequently pink, 2.2–5(–7) × 1.7–3.2 mm, apical notch 0.4–1.5 mm;

filaments usually cream, rarely light pink, those of longer stamens 2–3.5 mm, those of shorter ones 1–2 mm;

anthers cream to light yellow, 0.3–0.8 × 0.3–0.5 mm;

ovary 9–30 mm, densely strigillose and glandular puberulent;

style cream or yellow, 1.6–2.8 mm, stigma usually narrowly to broadly clavate, rarely subcapitate, 1–3 × 0.8–2 mm, surrounded by at least longer anthers.

erect, often hidden within subtending bracts, usually chasmogamous;

buds sessile, narrowly elongate, 2–4 mm;

floral tube 1.3–3.8 × 1–2.2 mm, ring of hairs 0.6–2 mm distal to base inside;

sepals 2–7.5 × 0.5–2.2 mm, apex acute;

petals rose-purple, magenta, pink, or white, 3–9.5(–11.5) × 1.2–5(–6.2) mm, apical notch 0.8–3.8 mm;

filaments dark pink, those of longer stamens 1.5–4.5 mm, those of shorter ones 0.5–1.9 mm;

anthers yellow, 0.5–1.2 × 0.3–0.7 mm;

ovary 2–5 mm, densely villous, often mixed glandular puberulent;

style white, 2.2–5.5(–7.5) mm, glabrous, stigma subcapitate to irregularly 4-lobed, 0.3–0.8 × 0.3–1 mm, surrounded by longer anthers.

Capsules

30–55(–70) mm, surfaces mixed strigillose and glandular puberulent; usually subsessile, rarely pedicel 1–5 mm, often appressed to stem.

cylindrical to subfusiform, 4–11 mm, beak to 0.5 mm, central column persistent, surfaces densely villous;

subsessile or pedicel 1–2.5 mm.

Seeds

very narrowly obovoid, 1–1.6(–1.8) × 0.4–0.6 mm, chalazal collar 0.1–0.2 mm, light brown or gray, surface rugose to papillose;

coma usually readily detached, white, 3–9 mm.

3–8 per locule, irregularly angular-fusiform, 1.2–1.6(–1.9) × 0.4–1 mm, without a chalazal collar, light brown, surface irregularly reticulate with raised cells.

2n

= 36.

= 20.

Epilobium saximontanum

Epilobium densiflorum

Phenology Flowering Jul–Sep. Flowering May–Oct.
Habitat Montane semi-shaded stream banks, damp meadows, mossy seeps, wet slatey cliffs, disturbed or seasonally damp areas. Vernally wet places, moist pastures, woodlands, meadows, along streams and ditches, alluvial valleys, often on low ground in volcanic or sandy soils.
Elevation 0–3700 m. (0–12100 ft.) 0–2600 m. (0–8500 ft.)
Distribution
from FNA
AZ; CA; CO; ID; MT; NM; NV; OR; SD; UT; WY; AB; BC; MB; NF; ON; QC
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; ID; MT; NV; OR; UT; WA; BC; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
Discussion

Epilobium saximontanum is morphologically similar to E. ciliatum (especially subsp. glandulosum) with which it also shares the AA chromosome arrangement. However, in addition to its fleshy compact turions, it very characteristically has notably appressed capsules, unlike most other species in the genus, and a notably strict habit.

The distribution of Epilobium saximontanum is unusual; it includes the Rocky Mountain region, only barely reaching the high southern Sierra Nevada, disjunct to the Black Hills of South Dakota, and more widely in eastern Canada, from the shores of Hudson Bay to Newfoundland. Specimens are fairly uniform across this wide and rather discontinuous range, although locally they show some variability, possibly due to hybridization with any of several species that may be sympatric with it. H. Lewis and D. M. Moore (1962) reported hybrids between E. saximontanum (cited as E. brevistylum) and E. ciliatum subsp. ciliatum (cited as E. adenocaulon) from Colorado, and herbarium specimens with E. saximontanum and apparent hybrids are not uncommon.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Epilobium densiflorum is an extremely variable species that changes its aspect through the flowering season. Collections made very early in the season may include only well-spaced, narrowly lanceolate leaves, the proximal ones usually opposite, and a short, sparse, somewhat open inflorescence. A late-season collection, even from the same population, may entirely lack cauline leaves, and consist instead of bare, peeling stems topped by dense, tightly imbricate-bracted inflorescences, with each broad bract enclosing a capsule or flower.

Boisduvalia douglasii Spach is an illegitimate substitute for Oenothera densiflora Lindley and pertains here.

(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. septentrionale, E. siskiyouense, 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. 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. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
Synonyms E. adenocaulon subsp. rubescens, E. drummondii, E. drummondii var. latiusculum, E. latiusculum, E. ovatifolium, E. rubescens, E. scalare, E. stramineum Oenothera densiflora, Boisduvalia bipartita, B. densiflora, B. densiflora var. bipartita, B. densiflora var. imbricata, B. densiflora var. montana, B. densiflora var. pallescens, B. densiflora var. salicina, B. imbricata, B. salicina, B. sparsiflora, B. sparsifolia, O. densiflora var. imbricata
Name authority Haussknecht: Oesterr. Bot. Z. 29: 119. (1879) (Lindley) Hoch & P. H. Raven: Phytologia 73: 457. (1993)
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