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

Humboldt County fuchsia, northern willowherb

Habit Herbs usually with taproot, sometimes with loose network of roots. Herbs usually not suffruticose, with basal shoots from thickened caudex, often decussate scales at base.
Stems

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.

decumbent, often matted, grayish green, terete, 5–25 cm, well-branched throughout, densely white-canescent proximally, mixed strigillose, villous, and glandular puberulent distally.

Leaves

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.

densely spaced, opposite proximal to inflorescence, alternate or fasciculate distally, petiole 0–2 mm, blade grayish green to green, lanceolate or elliptic to narrowly ovate, 1–3.5(–4) × 0.4–1.1 cm, base cuneate or attenuate, margins subentire to low-denticulate, 5–8 teeth per side, veins inconspicuous, 3–5 per side, apex acute, sometimes with caducous dark mucro, surfaces densely white-canescent and eglandular proximally, changing abruptly on inflorescence to glandular puberulent mixed with scattered villous;

bracts somewhat reduced.

Inflorescences

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

ascending spikes or racemes, densely glandular puberulent.

Flowers

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.

buds 12–15 × 4–5.5 mm, subsessile or pedicels 1–2 mm;

floral tube same color as petals, 17–23 × 3.5–5 mm, with ring of scales 4–5 mm from base inside;

sepals same color as petals, 7–12 × 2.5–3.5 mm;

petals red-orange, 8–14 × 5–6.5 mm, apical notch 1.8–2.4 mm;

filaments orange or red, those of longer stamens 15–17 mm, those of shorter ones 13–15 mm;

anthers 2.8–3.2 × 0.7–1 mm;

ovary 5–11 mm, glandular puberulent;

style light orange, 40–45 mm, stigma 4-lobed, 0.9–1.1 × 2.2–2.6 mm, exserted 8–10 mm beyond anthers.

Capsules

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

subsessile or pedicel 1–2.5 mm.

± straight, 20–26 mm, ± beaked, surfaces glandular puberulent;

sessile or pedicel 1–3 mm.

Seeds

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.

broadly to narrowly obovoid, with constriction 0.7–0.8 mm from micropylar end, 1.8–2.4 × 1.1–1.3 mm, chalazal collar inconspicuous, light brown, surface low-papillose;

coma easily detached, dingy white, 6–7 mm.

2n

= 20.

= 30.

Epilobium densiflorum

Epilobium septentrionale

Phenology Flowering May–Oct. Flowering Aug–Sep.
Habitat Vernally wet places, moist pastures, woodlands, meadows, along streams and ditches, alluvial valleys, often on low ground in volcanic or sandy soils. Rocky ledges and serpentine slopes along rivers.
Elevation 0–2600 m. (0–8500 ft.) 10–1900 m. (0–6200 ft.)
Distribution
from FNA
AZ; CA; ID; MT; NV; OR; UT; WA; BC; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[BONAP county map]
Discussion

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.)

Epilobium septentrionale is endemic to northern California, found only in the drainages of the Eel, Mattole, and Trinity rivers in Humboldt, Mendocino, and Trinity counties. The dimorphic pattern of vestiture on this species (eglandular, white-canescent lower leaves versus glandular puberulent upper leaves and bracts) is highly distinctive and not found in any specimens of E. canum. Most collections are relatively uniform in aspect, leaves, flowers, fruits, and seeds, despite the relative isolation from one another in the different river drainages where they occur.

S. R. Seavey and P. H. Raven (1977c) reported an experimental hybrid between Epilobium septentrionale and diploid E. canum subsp. canum; although it had normal chromosome pairing, pollen fertility was reduced (51%).

(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. Pachydium Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Zauschneria
Sibling taxa
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
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. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
Synonyms 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 Zauschneria septentrionalisd., E. canum subsp. septentrionale
Name authority (Lindley) Hoch & P. H. Raven: Phytologia 73: 457. (1993) (D. D. Keck) R. N. Bowman & Hoch: Ann. Missouri Bot. Gard. 66: 897. (1980)
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