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

rigid willowherb, Siskiyou Mountains. willowherb, stiff willowherb

Habit Herbs slender. Herbs from woody caudex forming hypogeal shoots with barklike periderm.
Stems

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

several to many, suberect or ascending, terete, 10–40 cm, simple or sparsely branched, usually glabrous and ± glaucous proximal to inflorescence, strigillose distally, sometimes densely strigillose throughout.

Leaves

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.

crowded distally, petiole 2–6 mm, blade narrowly ovate to ovate or broadly elliptic, often obovate in proximal pairs;

cauline 2–4.5 × 0.8–2 cm, base rounded to attenuate, margins subentire or finely denticulate, 8–12 teeth per side, lateral veins inconspicuous, 3–5 per side, apex obtuse proximally to subacute distally, surfaces glaucous and subglabrous to densely strigillose;

bracts narrower and much smaller.

Inflorescences

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

erect racemes, simple, ± densely strigillose, rarely mixed sparsely glandular puberulent.

Flowers

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.

erect;

buds 6–11 × 4–5 mm, apiculate;

pedicels 4–8 mm;

floral tube 1–1.8 × 2–3 mm, with raised ring of tissue edged with spreading hairs at mouth inside;

sepals often reddish green, lanceolate, 9.5–14.5 × 2.5–3.5 mm, apex acuminate, abaxial surface densely strigillose;

petals pink to rose-purple, obcordate, 16–20 × 13–16 mm, apical notch 3.4–5.5 mm;

filaments light pink, those of longer stamens 9–14 mm, those of shorter ones 6.5–10 mm;

anthers cream, 1.8–3.5 × 1–1.9 mm;

ovary 6–12 mm, densely strigillose;

style cream to light pink, 14.5–18.5 mm, stigma broadly 4-lobed, 1–1.5 × 3–3.5 mm, exserted beyond anthers.

Capsules

9–28 mm, surfaces strigillose and glandular puberulent;

pedicel 3–10 mm.

20–35 mm, surfaces strigillose;

pedicel 9–13 mm, bracts often attached 2–3 mm from base.

Seeds

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.

narrowly obovoid, constriction 0.6–0.8 mm from micropylar end, 2.5–3.4 × 0.9–1.4 mm, chalazal collar obscure, light brown, surface papillose;

coma easily detached, white, 6–8 mm.

2n

= 26.

= 36.

Epilobium minutum

Epilobium rigidum

Phenology Flowering Apr–Sep. Flowering Jul–Sep.
Habitat Open, dry places, along roads, disturbed areas. Dry rocky or sandy benches, rocky hillsides, dry streambeds in coniferous forests, on seasonally moist serpentine slopes, rarely along disturbed roadsides.
Elevation 90–1900 m. (300–6200 ft.) 100–1200(–1500) m. (300–3900(–4900) ft.)
Distribution
from FNA
CA; ID; MT; NV; OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

Within its range in northwestern California and southwestern Oregon, Epilobium rigidum is restricted to unusually dry habitats compared to most species in sect. Epilobium, but is not unlike taxa in the non-n = 18 clade, which are both perennial and annual. It is self-compatible, but with strongly protandrous flowers and an exserted stigma, and is modally outcrossing, pollinated by bees and flies.

Plant vestiture varies from subglabrous to densely strigillose throughout (var. canescens), but plants with these differences can be in the same population, and no other morphological differences between them have been found.

(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. Crossostigma Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Macrocarpa
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. 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. saximontanum, E. septentrionale, E. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
Synonyms E. minutum var. canescens E. rigidum var. canescens
Name authority Lindley in W. J. Hooker: Fl. Bor.-Amer. 1: 207. (1832) Haussknecht: Oesterr. Bot. Z. 29: 51. (1879)
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