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

pygmy willowherb, smooth boisduvalia, smooth spike-primrose, smooth willowherb

Habit Herbs usually with sessile, fleshy, underground turions, or sometimes thick, elongated shoots with dark, decussate scales. Herbs with 1 or more unbranched taproots.
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.

usually suberect, rarely matted, terete, 1.5–50 cm, often with sprawling, decumbent proximal branches, rarely simple, glabrous proximally or throughout, sometimes ± densely strigillose and/or villous 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.

crowded, subsessile, blade lanceolate to narrowly lanceolate or oblong, 0.8–3.5 × 0.2–0.6(–1) cm, longer than subtending internodes, base cuneate, margins evenly serrulate, 4–7 teeth per side, lateral veins obscure, 2–5 per side, apex acute, surfaces strigillose and ± villous, at least along veins and margins;

bracts not much reduced.

Inflorescences

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

erect spikes, congested, unbranched, densely strigillose and ± villous or subglabrous.

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 by subtending bracts, often cleistogamous;

buds 1.2–2 × 0.7–1.1 mm;

floral tube 0.3–1.1 × 0.2–0.8 mm, raised ciliate ring proximal to mouth inside;

sepals reddish green, 0.7–1.9 × 0.6–1.2 mm;

petals pale pink, fading purplish rose, 0.9–3.5 × 0.7–0.9 mm, apical notch 0.3–1.3 mm;

filaments light pink, those of longer stamens 0.5–1.5 mm, those of shorter ones 0.4–0.9 mm;

anthers pale yellow, 0.4–0.8 × 0.3–0.5 mm;

ovary 3–5 mm, usually densely villous;

style pale pink, 0.6–1.8 mm, stigma clavate, irregularly 4-lobed to subentire, 0.5–1 × 0.2–0.6 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, ± terete, 4.5–8 mm, beak 0.8–1 mm, usually dehiscing on distal 1/3, sometimes tardily splitting to base, central axis prematurely disintegrating, villous;

subsessile.

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.

7–14 per tightly packed row, irregularly angular-fusiform, 1–1.3 × 0.4–0.6 mm, chalazal collar absent, surface irregularly reticulate.

2n

= 36.

= 30.

Epilobium saximontanum

Epilobium campestre

Phenology Flowering Jul–Sep. Flowering May–Sep.
Habitat Montane semi-shaded stream banks, damp meadows, mossy seeps, wet slatey cliffs, disturbed or seasonally damp areas. Vernally moist flats, depressions, shores, and open fields, usually clay soils.
Elevation 0–3700 m. (0–12100 ft.) 30–3000 m. (100–9800 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; ND; NM; NV; OR; SD; UT; WA; WY; AB; BC; SK; Mexico (Baja California); South America (Argentina)
[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 campestre is widespread in temperate western North America. Like E. cleistogamum, it also grows in habitats that are only moist early in the growing season, or otherwise ephemeral moist places, like shores of reservoirs with fluctuating water levels(P. H. Raven and D. M. Moore 1965), and consequently flowers earlier than most species of Epilobium.

The occurrence of this species in Chubut Province, Argentina, appears to be the result of natural long-distance dispersal, probably by birds.

Seeds of Epilobium campestre are inclined about 20° from vertical, which while unique and characteristic is a difficult character to observe. Seeds are tightly packed in rigid capsules, as described under E. cleistogamum.

Oenothera pygmaea Spegazzini 1899, an illegitimate name (not Douglas 1832), 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. Epilobiopsis
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. 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. 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 Boisduvalia campestris, B. glabella, B. glabella var. campestris, B. pygmaea, E. pygmaeum, Oenothera glabella
Name authority Haussknecht: Oesterr. Bot. Z. 29: 119. (1879) (Jepson) Hoch & W. L. Wagner: Syst. Bot. Monogr. 83: 208. (2007)
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