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bog willow-herb, linearleaf willowweed, narrow-leaf willowherb, slender leaf willowherb, épilobe leptophylle

California willowherb, chaparral willowherb, desert willowherb, little willowherb, minute willowherb, small-flower willowherb

Habit Herbs with threadlike, nearly leafless epigeous stolons terminating in compact, fleshy turions 3–8 × 2–4 mm. Herbs slender.
Stems

erect, simple to loosely clustered, terete, 15–95 cm, simple to well branched, densely strigillose, often mixed glandular puberulent on inflorescence, rarely with faint strigillose lines decurrent from margins of petioles.

strict, erect, sometimes reddish green, terete, 3.5–40 cm, simple or freely branched, subglabrous proximally to strigillose and glandular puberulent distally.

Leaves

opposite proximally, usually alternate, rarely fasciculate distally, subsessile;

blade linear to very narrowly elliptic or sublanceolate, 2–7.5 × 0.1–0.7 cm, usually longer than internodes, base rounded to subcuneate, margins subentire, 4–7 inconspicuous teeth per side, sometimes revolute, lateral veins inconspicuous, apex obtuse proximally to acute distally, both surfaces densely strigillose, increasing distally;

bracts not much reduced.

alternate distally, not fasciculate, petiole 0–2 mm, blade subspatulate proximally to lanceolate, oblanceolate, or narrowly elliptical distally, not folded along midrib, 0.9–2.5 × 0.2–0.6 cm, shorter than internodes, base tapered, margins entire or scarcely denticulate, 1–4 teeth per side, lateral veins obscure, apex subacute or often blunt proximally, surfaces subglabrous or with scattered hairs along margins;

bracts much reduced, sometimes attached to pedicel.

Inflorescences

erect racemes, densely strigillose, often mixed sparsely glandular puberulent.

erect racemes or open panicles, relatively loose and uncrowded, branches thin, mixed strigillose and glandular puberulent.

Flowers

erect;

buds 3–5 × 1.5–2.5 mm;

pedicel 5–12 mm;

floral tube 0.8–1.5 × 1.2–1.8 mm, ring of spreading hairs at mouth inside;

sepals 2.5–4.5 × 0.9–1.3 mm, abaxial surface strigillose;

petals obcordate, white to light pink, 3.5–7 × 1.6–4 mm, apical notch 1–1.8 mm;

filaments white or cream, those of longer stamens 0.8–3.5 mm, those of shorter ones 0.6–2.5 mm;

anthers cream, 0.5–0.9 × 0.4–0.6 mm;

ovary 12–18 mm, densely strigillose, sometimes mixed glandular puberulent;

style cream, 2–3.8 mm, stigma narrowly clavate, entire, 1–1.8 × 0.5–1.2 mm, usually surrounded by, rarely exserted beyond, anthers.

erect or, sometimes, nodding in bud;

buds broadly ovoid, 1.2–2.5 × 1–1.5 mm;

floral tube 1.1–1.5 × 1–1.4 mm, usually with ring of spreading hairs at mouth inside;

sepals 0.5–2.5 × 0.4–1.3 mm, apex acute, abaxial surface strigillose, sometimes mixed glandular puberulent;

petals white to pink, 2–5 × 1.5–3 mm, apical notch 0.2–1.9 mm;

filaments white, those of longer stamens 0.5–3 mm, those of shorter ones 0.3–2 mm;

anthers 0.6–1 × 0.5–0.8 mm;

ovary 4–9 mm, mixed strigillose and glandular puberulent;

style light pink, 1–3.5 mm, stigma subclavate to obscurely 4-lobed, 0.4–0.6 × 0.4–0.5 mm, surrounded by longer anthers.

Capsules

straight, narrowly cylindrical, 35–80 mm, surfaces densely strigillose;

pedicel 10–35 mm.

9–28 mm, surfaces strigillose and glandular puberulent;

pedicel 3–10 mm.

Seeds

narrowly fusiform to narrowly obovoid, 1.5–2.2 ×0.5–0.7 mm, chalazal collar 0.1–0.2 mm, ± pronounced, surface papillose;

coma persistent, dingy white, 6–8 mm.

obovoid, without constriction, 0.9–1.2 × 0.4–0.6 mm, low chalazal collar 0.1–0.2 mm wide, brown, surface reticulate;

coma easily detached, white, 2.5–3 mm.

2n

= 36.

= 26.

Epilobium leptophyllum

Epilobium minutum

Phenology Flowering Jun–Sep. Flowering Apr–Sep.
Habitat Marshy ground, bogs, fens, low thickets, seepage areas, damp pastures. Open, dry places, along roads, disturbed areas.
Elevation 0–1000(–2900) m. (0–3300(–9500) ft.) 90–1900 m. (300–6200 ft.)
Distribution
from FNA
AK; CA; CO; CT; IA; ID; IL; IN; KS; KY; MA; MD; ME; MI; MN; MO; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; SPM
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; MT; NV; OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

The range of Epilobium leptophyllum overlaps with that of the related E. palustre, but the former is less common to the north and more common south into the midwestern United States, and absent only from most of the southern tier of states. It is also relatively uncommon in the western United States and Canada. Judging by the number of herbarium sheets that also include E. palustre, E. densum, and even E. coloratum, it sometimes occurs in sympatry with those species and may rarely hybridize with them, based on plants with intermediate morphology and/or sterile fruits.

Fernald described Epilobium nesophilum from the Magdalen Islands (Quebec), and especially Newfoundland, first as a variety of E. densum (1918), then as a separate species (1925).

Epilobium rosmarinifolium Pursh 1813, an illegitimate name (not Haenke 1788), pertains here.

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

Epilobium minutum, like the similar E. foliosum, also occasionally produces cleistogamous flowers, and is modally autogamous in any event. S. R. Seavey et al. (1977b) observed that E. minutum is less common than E. foliosum in the southern part of their overlapping ranges and more common in the north. Several sheets (for example, Lawler 3276, California, Butte Co. [MO]; Nelson & Gordon 5573, California, Trinity Co. [MO]) mention that the plants were growing on serpentine soil. The earliest collection of this species appears to be one made by Archibald Menzies in 1792–1794 under the name E. palustre (BM).

Crossostigma lindleyi Spach (a substitute name for Epilobium minutum) and E. lindleyi (Spach) Rydberg are illegitimate names that pertain 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. Crossostigma
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. 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. 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. densum var. nesophilum, E. nesophilum, E. oliganthum var. gracile, E. palustre var. gracile, E. squamatum, E. tenellum E. minutum var. canescens
Name authority Rafinesque: Précis Découv. Somiol., 41. (1814) Lindley in W. J. Hooker: Fl. Bor.-Amer. 1: 207. (1832)
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