View source for Epilobium

{{Treatment/ID
|accepted_name=Epilobium
|accepted_authority=Linnaeus
|publications={{Treatment/Publication
|title=Sp. Pl.
|place=1: 347. 1753
|year=1753
}}
|common_names=Willowherb
|basionyms=
|synonyms=
|hierarchy=Onagraceae;Onagraceae subfam. Onagroideae;Onagraceae tribe Epilobieae;Epilobium
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Onagraceae]]</div><div class="higher-taxon"><small>subfamily</small>[[Onagraceae subfam. Onagroideae]]</div><div class="higher-taxon"><small>tribe</small>[[Onagraceae tribe Epilobieae]]</div><div class="higher-taxon"><small>genus</small>[[Epilobium]]</div></div>
|etymology=Greek epi, on, lobos, pod or capsule, and iov (ion), violet, alluding to violet flower at apex of fruit
|volume=Volume 10
|mention_page=
|treatment_page=
}}<!--

--><span class="statement" id="st-d0_s0" data-properties="herb duration;herb duration;herb growth form;herb architecture;turion texture;turion arrangement"><b>Herbs,</b> annual or perennial, sometimes suffrutescent, caulescent, often with basal rosettes, fleshy decussate turions, soboles, stolons, which may tipped with turions, or rarely buds (gemmae) in leaf-axils;</span> <span class="statement" id="st-d0_s1" data-properties="stolon architecture">with woody base or caudex, or with taproots.</span> <span class="statement" id="st-d0_s2" data-properties="stem orientation;stem orientation;stem orientation;stem orientation;stem architecture;stem architecture;stem architecture;stem relief;stem pubescence;stem pubescence;stem pubescence;stem arrangement;stem pubescence;species position;line prominence;line pubescence;line shape"><b>Stems </b>erect to ascending or decumbent, simple to well-branched distally or sometimes from base, in some species proximal epidermis exfoliating, strigillose, glandular-puberulent, villous, often mixed, or glabrous, often with raised hairy lines decurrent from leaf-axils.</span> <span class="statement" id="st-d0_s3" data-properties="leaf position;leaf position;leaf arrangement;leaf arrangement;leaf position;leaf architecture or arrangement"><b>Leaves </b>cauline, sometimes also basal, opposite and decussate proximal to inflorescence or only in proximal pairs, or rarely throughout, alternate or, sometimes, fasciculate distally;</span> <span class="statement" id="st-d0_s4" data-properties="">stipules absent;</span> <span class="statement" id="st-d0_s5" data-properties="stipule presence;stipule architecture;stipule architecture;stipule architecture">subsessile to petiolate;</span> <span class="statement" id="st-d0_s6" data-properties="blade margin shape;blade margin shape">blade margins entire or toothed;</span> <span class="statement" id="st-d0_s7" data-properties="bract size">bracts usually reduced distally.</span> <span class="statement" id="st-d0_s8" data-properties="inflorescence position or structure subtype;flower architecture or arrangement or growth form;flower orientation;flower orientation;flower life cycle"><b>Inflorescences </b>terminal, usually racemes or spikes, rarely panicles, flowers solitary in leaf-axils, erect or ascending, sometimes also flowering from proximal nodes;</span> <span class="statement" id="st-d0_s9" data-properties="bracteole presence">bracteoles absent.</span> <span class="statement" id="st-d0_s10" data-properties="flower reproduction;flower architecture;flower architecture;bud orientation;bud orientation"><b>Flowers </b>bisexual, usually actinomorphic, rarely zygomorphic, buds often erect, sometimes recurved;</span> <span class="statement" id="st-d0_s11" data-properties="floral-tube duration;base life cycle;base shape;base shape;base architecture;ring prominence;nectary prominence">floral-tube deciduous (with sepals, petals, and stamens) after anthesis, obconic or cylindrical, sometimes with bulbous base, with scales or ring of hairs or raised ring of tissue near mouth inside, nectary at base of tube;</span> <span class="statement" id="st-d0_s12" data-properties="sepal quantity;sepal orientation;sepal coloration;sepal coloration;sepal coloration;sepal coloration">sepals 4, spreading individually, usually green or flushed with red or cream, rarely same color as petals, lanceolate;</span> <span class="statement" id="st-d0_s13" data-properties="petal quantity;petal coloration;petal coloration;petal coloration;petal coloration;petal coloration;petal coloration;petal coloration;petal coloration;petal coloration;petal coloration;petal shape;petal shape;petal architecture or shape">petals 4, usually rose-purple to white, rarely cream-yellow or orange-red, usually obcordate or broadly obovate, emarginate;</span> <span class="statement" id="st-d0_s14" data-properties="stamen quantity;stamen arrangement;series quantity;series size;anther position;anther size;anther size;anther orientation;anther fixation;pollen fixation">stamens 8, in 2 unequal series with episepalous longer or rarely subequal, erect, anthers versatile, on smallest flowers appearing basifixed, pollen usually shed in tetrads, rarely singly;</span> <span class="statement" id="st-d0_s15" data-properties="ovary architecture or structure in adjective form;style orientation;stigma architecture or shape;stigma shape;stigma shape;stigma shape;stigma shape;stigma shape;stigma shape;stigma shape;stigma shape;stigma structure in adjective form;surface condition or texture;papilla architecture">ovary 4-locular, style erect, stigma entire and clavate to capitate, or deeply 4-lobed, commissural, receptive only on inner surfaces, surface dry with multicellular papillae.</span> <span class="statement" id="st-d0_s16" data-properties="central column condition;central column dehiscence"><b>Fruit </b>a capsule, straight or slightly curved, narrowly cylindrical to fusiform or rarely narrowly ellipsoidal, usually terete, rarely ± 4-angled, loculicidally dehiscent, usually splitting to base with intact central column, rarely splitting only on distal 1/3 with central column disintegrating;</span> <span class="statement" id="st-d0_s17" data-properties="fruit course;fruit course;fruit shape;fruit shape;fruit shape;fruit shape;fruit shape;fruit shape;fruit dehiscence;fruit architecture or dehiscence;fruit architecture or dehiscence;fruit architecture;fruit architecture;capsule course;capsule course;capsule shape;capsule shape;capsule shape;capsule shape;capsule shape;capsule shape;capsule dehiscence;capsule architecture or dehiscence;capsule architecture or dehiscence;capsule architecture;capsule architecture">pedicellate or sessile.</span> <span class="statement" id="st-d0_s18" data-properties="seed quantity;seed quantity;seed quantity;locule quantity;rim shape;coma duration;coma presence"><b>Seeds </b>usually numerous (1–100+ per locule), usually in 1, rarely 2, rows per locule, very rarely 1 row per capsule by dissolution of septa and central column, surface papillose to finely reticulate or longitudinally ridged, sometimes constricted near micropylar end, rarely with inflated rim around body of seed on adaxial side, with persistent coma at chalazal end or coma absent.</span> <span class="statement" id="st-d0_s19" data-properties="surface relief;surface relief;surface relief;surface shape;surface size;surface quantity;surface quantity;surface quantity;surface quantity;surface quantity;surface quantity;surface quantity;surface quantity">= 9, 10, 12, 13, 15, 16, 18, 19.</span><!--

-->{{Treatment/Body
|distribution=North America;Mexico;West Indies;Central America;South America;Eurasia;Africa;Pacific Islands (New Zealand);Australasia
|discussion=<p>Species ca. 165 (41 in the flora).</p><!--
--><p>Epilobium is the largest genus in Onagraceae, distributed mainly in cool temperate, montane, boreal, and arctic areas on all continents except Antarctica. P. H. Raven (1976) proposed many elements of the current classification of Epilobieae, recognizing six sections in Epilobium, including for the first time the genus Zauschneria as a separate section, based on patterns of variation in chromosome number (H. Lewis and Raven 1961; M. Kurabayashi et al. 1962), wood anatomy (S. Carlquist 1975), seed morphology (S. R. Seavey et al. 1977), and pollen wall (J. J. Skvarla et al. 1976) and viscin thread morphology (Skvarla et al. 1978). Raven excluded Boisduvalia from Epilobium, though it later was included (P. C. Hoch and Raven 1992) as two distinct sections, and Raven included Chamaenerion as a section, which was later excluded (Hoch and Raven 1999; W. L. Wagner et al. 2007). Both of these changes from the 1976 classification were based in large part on relationships supported by molecular data (D. A. Baum et al. 1994). The monophyly of this re-defined Epilobium was very strongly supported in analyses of ITS alone (Baum et al.) and ITS plus trnL-F (R. A. Levin et al. 2004), as was the segregation of Chamaenerion from Epilobium. In addition, both analyses strongly supported a clade that includes the former segregated genera Boisduvalia and Zauschneria as well as the sections of Epilobium with chromosome numbers other than n = 18. As treated here, Epilobium is divided into eight sections, one of which has two subsections (Wagner et al.).</p><!--
--><p>The phylogeny of Epilobium as elucidated by D. A. Baum et al. (1994) and later R. A. Levin et al. (2004) suggests complex chromosomal evolution in the genus. Since the outgroup (Chamaenerion) and one major clade (sect. Epilobium) share the base number x = 18, the derivation of the diverse other gametic numbers (n = 9, 10, 12, 13, 15, 16, and 19) appears to have involved aneuploid reduction from x = 18. One explanation of the relationships proposed by the molecular data suggests the early evolution of a lineage with n = 15 (sects. Cordylophorum, Epilobiopsis, and Zauschneria), from which arose a branch with n = 12 (sect. Xerolobium), a separate branch with n = 13 and n = 16 (sect. Crossostigma), and a third branch with n = 9, 10, and 19 (sect. Pachydium). This hypothesis requires the fewest aneuploidy changes, but confirming it will require additional molecular and cytological analysis.</p><!--
--><p>Almost all Epilobium species tested are self-compatible, but at least E. obcordatum is apparently self-incompatible (S. R. Seavey and S. K. Carter 1994, 1996). All species have hermaphroditic, diurnal flowers that usually remain open for more than one day. Many species are modally autogamous, a few primarily cleistogamous, but others, including 15 species in North America, are partly or wholly outcrossing. In the latter group, flowers are often markedly protandrous, with a 4-lobed stigma exserted beyond anthers. Primary pollinators include bees, flower flies, butterflies, moths, and sometimes hummingbirds (sect. Zauschneria). In general, flowering commences in the first year of growth.</p><!--
--><p>Only the nine species (eight in the flora area) of sects. Pachydium, Crossostigma, Epilobiopsis, and Xerolobium are annuals; all other taxa of Epilobium (sects. Cordylophorum, Epilobium, Macrocarpa, and Zauschneria) are perennials. Annual species have taproots and proximal stems usually with peeling epidermis. Perennial species of Epilobium, which have more fibrous root systems and rarely peeling epidermis, vary greatly in the habit and stature, degree of clumping, degree of branching, and mode of perennation.</p><!--
--><p>The various types of perennating structures in Epilobium (R. C. Keating et al. 1982; Chen C. J. et al. 1992) are extremely useful for identification of many taxa; unfortunately, many plants are collected without the structures. Unless care is taken to dig up the bases of the plants, some of the most useful diagnostic features such as turions are lost, making identification more difficult. Perennating structures are less useful for phylogenetic analysis due to the difficulty in determining whether the common possession of a particular type represents an analogous or homologous pattern. However, one type of structure (soboles) is found in at least some taxa of all perennial sections and may be the most generalized type in the genus.</p><!--
--><p>Soboles are here defined as simple, scaly, underground shoots with somewhat elongated internodes and arising from the caudex. Soboles generally give rise to more or less clumped plants with ascending stems. In certain species, including Epilobium rigidum (sect. Macrocarpa), all taxa of sects. Cordylophorum and Zauschneria, and some in sect. Epilobium, soboles arise from more or less woody caudices, a character state that may be plesiomorphic in the genus; all other types of perennating structures are found only in sect. Epilobium and are discussed there.</p><!--
--><p>In addition to habit and perennating structures, certain other morphological features particularly useful for diagnosing plants include: leaf size, shape, attachment, and arrangement on stem; seed surface (papillose, reticulate, or ridged), size, and shape (S. R. Seavey et al. 1977); pubescence type (mainly strigillose: short incurved hairs; villous: long, thin, spreading hairs; and/or glandular-puberulent) and pattern on stem (all around or restricted to raised lines decurrent from base of petioles) and leaves; and some floral features including size, shape, and color. In fact, floral features are diagnostic for only certain sections or species; most species have very similar flowers.</p>
|tables=
|references=
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Herbs annual, with taproot, stem epidermis peeling proximally; leaves opposite in proximal pairs, alternate or fasciculate distally.
|[[#key-0-2| > 2]]
|-id=key-0-2
|2
|Seed coma usually present, very rarely absent, often easily or readily detached.
|[[#key-0-3| > 3]]
|-id=key-0-3
|3
|Herbs 15–200 cm; floral tubes 1–16 mm, sepals 1–8.5 mm, petals 1.5–15(–20) mm; seeds 1.5–2.7 mm; pollen usually shed singly, rarely in tetrads [.
|[[Epilobium sect. Xerolobium] 2. Epilobium brachycarpum|Epilobium sect. Xerolobium] 2. Epilobium brachycarpum]]
|-id=key-0-3
|3
|Herbs 5–45 cm; floral tubes 0.4–1.5 mm, sepals 0.5–2.5 mm, petals 1.4–5 mm; seeds 0.6–1.2 mm; pollen shed in tetrads [.
|[[Epilobium sect. Crossostigma].|Epilobium sect. Crossostigma].]]
|-id=key-0-4
|4
|Leaves usually folded along midrib, often fasciculate distally; inflorescences congested; petals 1.4–2.5 mm; seeds 0.6–0.9 mm, surface papillose.
|[[Epilobium foliosum|Epilobium foliosum]]
|-id=key-0-4
|4
|Leaves flat, not fasciculate; inflorescences not congested; petals 2–5 mm; seeds 0.9–1.2 mm, surface reticulate.
|[[Epilobium minutum|Epilobium minutum]]
|-id=key-0-2
|2
|Seed coma absent.
|[[#key-0-5| > 5]]
|-id=key-0-5
|5
|Capsule walls tough, usually splitting only in distal 1/3; seeds in 2 rows per locule; often with decumbent proximal branches; flowers usually cleistogamous [.
|[[Epilobium sect. Epilobiopsis].|Epilobium sect. Epilobiopsis].]]
|-id=key-0-6
|6
|Capsules 8–12 mm, sharply 4-angled; sepals 1.5–3 mm; seeds 1.2–1.5 mm.
|[[Epilobium cleistogamum|Epilobium cleistogamum]]
|-id=key-0-6
|6
|Capsules 4.5–8 mm, subterete; sepals 0.7–1.9 mm; seeds 1–1.3 mm.
|[[Epilobium campestre|Epilobium campestre]]
|-id=key-0-5
|5
|Capsule walls flexible, splitting to base; seeds in 1 row per locule or compressed to 1 row per capsule; proximal branches ascending, erect, or absent; flowers chasmogamous or cleistogamous [.
|[[Epilobium sect. Pachydium].|Epilobium sect. Pachydium].]]
|-id=key-0-7
|7
|Capsules with beak 0–0.5 mm, septifragal, septa adherent to intact central axis; bracts wider than cauline leaves.
|[[Epilobium densiflorum|Epilobium densiflorum]]
|-id=key-0-7
|7
|Capsules with beak 2–5 mm, loculicidal, septa adhering to valves, central axis disintegrating; bracts not wider than cauline leaves.
|[[#key-0-8| > 8]]
|-id=key-0-8
|8
|Floral tubes 1.5–3 mm, sepals (1.5–)2–6 mm, petals (2.8–)3.5–10 mm; capsules (10–)14–21 mm; seeds in 1 staggered row distally, 1.8–2.3 mm; flowers ± chasmogamous.
|[[Epilobium pallidum|Epilobium pallidum]]
|-id=key-0-8
|8
|Floral tubes 0.4–1 mm, sepals 0.7–2 mm, petals 1.2–3.2 mm; capsules (6–)8–14 mm; seeds in 4 rows (1 row per locule), 0.9–1.6 mm; flowers ± cleistogamous.
|[[Epilobium torreyi|Epilobium torreyi]]
|-id=key-0-1
|1
|Herbs perennial, sometimes woody, ± without taproot, stem epidermis usually not peeling, sometimes peeling proximally; leaves usually opposite proximal to inflorescences, alternate distally, not fasciculate.
|[[#key-0-9| > 9]]
|-id=key-0-9
|9
|Floral tubes 16–32 mm, bulbous near base, irregular scales at mouth inside; flowers: floral tube, sepals, and petals usually orange-red, very rarely white, slightly zygomorphic, upper petals ± flared at right angle to calyx tube [.
|[[Epilobium sect. Zauschneria].|Epilobium sect. Zauschneria].]]
|-id=key-0-10
|10
|Herbs clumped perennials to subshrubs, 10–120 cm; leaves not dimorphic, usually mixed pubescent, rarely glabrate, not white-canescent.
|[[Epilobium canum|Epilobium canum]]
|-id=key-0-10
|10
|Herbs matted perennials, 5–25 cm; leaves dimorphic, proximal ones densely white-canescent and eglandular, distal ones glandular puberulent and scattered villous, not canescent.
|[[Epilobium septentrionale|Epilobium septentrionale]]
|-id=key-0-9
|9
|Floral tubes 0.3–9.5 mm, not or very rarely bulbous near base, scales absent; flowers: floral tube and sepals green or flushed reddish green, petals usually pink, white, or rose-purple, rarely cream, usually actinomorphic, very rarely slightly zygomorphic.
|[[#key-0-11| > 11]]
|-id=key-0-11
|11
|Herbs suffrutescent or rhizomatous, rarely herbaceous; proximal stem epidermis usually peeling; stigmas 4-lobed; seeds 1.5–3.4 mm, ± prominently constricted near micropylar end.
|[[#key-0-12| > 12]]
|-id=key-0-12
|12
|Leaf blades 20–45 mm, not folded on midrib; sepals 9.5–14.5 mm; petals 16–20 mm; floral tubes 1–1.8 mm [.
|[[Epilobium sect. Macrocarpa] 1. Epilobium rigidum|Epilobium sect. Macrocarpa] 1. Epilobium rigidum]]
|-id=key-0-12
|12
|Leaf blades 9–25 mm, folded on midrib or not; sepals 2.6–6.5 mm; petals 5–9.5 mm; floral tubes 1.8–9.5 mm [.
|[[Epilobium sect. Cordylophorum].|Epilobium sect. Cordylophorum].]]
|-id=key-0-13
|13
|Leaf blades not folded on midrib; petals cream to light yellow; flowers slightly zygomorphic (upper petals slightly longer, styles declined); sepals 4–6.5 mm; capsules 10–30 mm; seeds 4–8+ seeds per locule; ovaries eglandular.
|[[Epilobium suffruticosum|Epilobium suffruticosum]]
|-id=key-0-13
|13
|Leaf blades ± folded on midrib; petals rose-purple; flowers not zygomorphic; sepals 2.6–4.4 mm; capsules 8–16 mm; seeds 1–3 per locule; ovaries glandular pubescent.
|[[#key-0-14| > 14]]
|-id=key-0-14
|14
|Leaf blade margins denticulate, surfaces usually glabrescent, rarely strigillose-villous; floral tubes 2.7–3.2(–5) mm; seeds 2.1–2.9 mm.
|[[Epilobium nevadense|Epilobium nevadense]]
|-id=key-0-14
|14
|Leaf blade margins subentire or low-denticulate, surfaces densely spreading-hairy; floral tubes 5.2–9.5 mm; seeds 1.5–2.4 mm.
|[[Epilobium nivium|Epilobium nivium]]
|-id=key-0-11
|11
|Herbs herbaceous or, sometimes, ± suffrutescent; proximal stem epidermis not peeling; stigmas entire or 4-lobed; seeds 0.8–2.2 mm, not constricted near micropylar end [.
|[[Epilobium sect. Epilobium].|Epilobium sect. Epilobium].]]
|-id=key-0-15
|15
|Stigmas 4-lobed, exserted beyond or rarely surrounded by anthers; floral tubes 1–5.5 mm; sepals (2.5–)5–14 mm; petals (4–)8–26 mm.
|[[#key-0-16| > 16]]
|-id=key-0-16
|16
|Petals cream-yellow; seed coma tawny, persistent.
|[[Epilobium luteum|Epilobium luteum]]
|-id=key-0-16
|16
|Petals pink to rose-purple; seed coma white, dull white, or dingy, sometimes tawny, ± easily or readily detached.
|[[#key-0-17| > 17]]
|-id=key-0-17
|17
|Herbs ± suffrutescent, forming shoots from woody caudex; stems 5–25 cm, clumped to cespitose; floral tubes 2.1–5.5 mm.
|[[#key-0-18| > 18]]
|-id=key-0-18
|18
|Herbs ± glabrous and glaucous proximal to inflorescences; leaf blades 6–18(–24) mm; floral tubes 3.2–5.5 mm, slightly raised ring of tissue inside.
|[[Epilobium obcordatum|Epilobium obcordatum]]
|-id=key-0-18
|18
|Herbs pubescent throughout, not glaucous; leaf blades 13–26 mm; floral tubes 2.1–4 mm, prominent raised ring of tissue inside.
|[[Epilobium siskiyouense|Epilobium siskiyouense]]
|-id=key-0-17
|17
|Herbs herbaceous, forming basal rosettes, stolons, turions, or soboles; stems (5–)15–120(–250) cm, erect, sometimes clumped; floral tubes 1–3 mm.
|[[#key-0-19| > 19]]
|-id=key-0-19
|19
|Stems densely villous, often mixed glandular puberulent proximal to inflorescences, 18–120(–250) cm.
|[[#key-0-20| > 20]]
|-id=key-0-20
|20
|Leaves sessile, clasping; sepals 6–12 mm; petals 9–20 mm; herbs with thick stolons sometimes terminating in rosette.
|[[Epilobium hirsutum|Epilobium hirsutum]]
|-id=key-0-20
|20
|Leaves with petioles 1–3 mm proximally, subsessile distally, not clasping; sepals 2.5–6 mm; petals 4–8.5 mm; herbs with short-stalked leafy rosettes.
|[[Epilobium parviflorum|Epilobium parviflorum]]
|-id=key-0-19
|19
|Stems densely strigillose to ± glabrous proximal to inflorescences, not villous, (5–)15–75 cm.
|[[#key-0-21| > 21]]
|-id=key-0-21
|21
|Stems densely strigillose proximal to inflorescences; seeds densely papillose; sepals 5–6.5 mm; petals 7.5–10 mm.
|[[Epilobium montanum|Epilobium montanum]]
|-id=key-0-21
|21
|Stems ± glabrous and glaucous proximal to inflorescences; seeds ridged; sepals 6–10 mm; petals (6–)10–15 mm.
|[[Epilobium oreganum|Epilobium oreganum]]
|-id=key-0-15
|15
|Stigmas entire, clavate or capitate, surrounded by or, rarely, exserted beyond anthers; floral tubes 0.3–2.6 mm; sepals 1.1–7.5 mm; petals 1.6–10(–14) mm.
|[[#key-0-22| > 22]]
|-id=key-0-22
|22
|Herbs with ± threadlike stolons, with or without terminal turions; stems usually erect from base, rarely ascending.
|[[#key-0-23| > 23]]
|-id=key-0-23
|23
|Stolons terminating in fleshy turions; stems (5–)15–95 cm, simple to well branched.
|[[#key-0-24| > 24]]
|-id=key-0-24
|24
|Stems densely villous, without raised lines from margins of petioles.
|[[Epilobium densum|Epilobium densum]]
|-id=key-0-24
|24
|Stems strigillose to subglabrous, not villous, sometimes with faint raised strigillose lines from margins of petioles.
|[[#key-0-25| > 25]]
|-id=key-0-25
|25
|Leaf blade surfaces strigillose abaxially, subglabrous adaxially, with strigillose margins and veins; inflorescences nodding in bud.
|[[Epilobium palustre|Epilobium palustre]]
|-id=key-0-25
|25
|Leaf blade surfaces densely strigillose on both sides; inflorescences erect in bud.
|[[Epilobium leptophyllum|Epilobium leptophyllum]]
|-id=key-0-23
|23
|Stolons not terminating in turions; stems 5–30 (–40) cm, usually simple, rarely branched, rarely stems 20–80 cm, well branched.
|[[#key-0-26| > 26]]
|-id=key-0-26
|26
|Leaf blades 1.5–10 cm; stems 20–80 cm, well branched, not clumped or matted.
|[[Epilobium obscurum|Epilobium obscurum]]
|-id=key-0-26
|26
|Leaf blades 0.4–2.1 cm; stems 5–30(–40) cm, not or rarely branched, ± loosely clumped or matted.
|[[#key-0-27| > 27]]
|-id=key-0-27
|27
|Stems subglabrous, often matted, 8–30(–40) cm; leaf blades broadly elliptic proximally, narrowly elliptic or lanceolate to sublinear distally.
|[[Epilobium oregonense|Epilobium oregonense]]
|-id=key-0-27
|27
|Stems densely glandular puberulent, loosely clumped, 5–20 cm; leaf blades broadly obovate to orbiculate proximally to ovate or lanceolate distally.
|[[Epilobium howellii|Epilobium howellii]]
|-id=key-0-22
|22
|Herbs with rosettes, turions, fleshy soboles or shoots; stem bases erect or ascending.
|[[#key-0-28| > 28]]
|-id=key-0-28
|28
|Herbs with small-leafed epigeous or scaly hypogeous soboles; stems usually ± ascending, rarely erect, ± clumped or matted, rarely with basal scales.
|[[#key-0-29| > 29]]
|-id=key-0-29
|29
|Stems 8–75(–85) cm, glabrous and ± glaucous proximal to inflorescences, often without raised lines; leaves subsessile, ± clasping; seeds 0.7–1(–1.3) mm, surfaces densely papillose.
|[[Epilobium glaberrimum|Epilobium glaberrimum]]
|-id=key-0-29
|29
|Stems 3–50 cm, subglabrous or strigillose, not glaucous, proximal to inflorescences, with distinct raised strigillose lines decurrent from margins of petioles; leaves subsessile or with petiole 1–12 mm, not clasping; seeds 0.7–2.1 mm, surfaces reticulate to densely papillose.
|[[#key-0-30| > 30]]
|-id=key-0-30
|30
|Stems strigillose proximal to inflorescences, densely glandular puberulent distally.
|[[Epilobium smithii|Epilobium smithii]]
|-id=key-0-30
|30
|Stems subglabrous with raised strigillose lines proximal to inflorescences, mixed strigillose and glandular puberulent or subglabrous distally.
|[[#key-0-31| > 31]]
|-id=key-0-31
|31
|Stems 10–50 cm; leaf blades 1.5–6.2 × 0.7–2.9 cm, margins denticulate; capsules 35–100 mm.
|[[#key-0-32| > 32]]
|-id=key-0-32
|32
|Petals usually pink to rose-purple, rarely white; pedicels 5–15(–25) mm in fruit; capsules 35–65 mm; petioles 3–9 mm proximally, to 0 mm distally, not winged; seed surfaces usually papillose, sometimes reticulate.
|[[Epilobium hornemannii|Epilobium hornemannii]]
|-id=key-0-32
|32
|Petals white, rarely red-veined or fading pink; pedicels 15–45 mm in fruit; capsules 50–100 mm; petioles 3–12 mm, often winged; seed surfaces reticulate or, sometimes, barely rugose.
|[[Epilobium lactiflorum|Epilobium lactiflorum]]
|-id=key-0-31
|31
|Stems 3–20(–25) cm; leaf blades (0.5–)0.7–2.8 × 0.3–1.6 cm, margins subentire to sparsely denticulate; capsules 17–40(–55) mm.
|[[#key-0-33| > 33]]
|-id=key-0-33
|33
|Herbs with thin leafy soboles, no woody rootstock, densely clumped or matted, stems nodding in bud; pedicels 5–35(–68) mm in fruit; seeds 0.7–1.4 mm; stems subglabrous, rarely mixed strigillose and sparsely glandular puberulent distally.
|[[Epilobium anagallidifolium|Epilobium anagallidifolium]]
|-id=key-0-33
|33
|Herbs with wiry, scaly soboles and extended semi-woody rootstock, clumped, stems ± erect; pedicels 2–21 mm in fruit; seeds (1.3–)1.5–2.1 mm; stems subglabrous proximally, ± densely strigillose and mixed glandular- puberulent distally.
|[[Epilobium clavatum|Epilobium clavatum]]
|-id=key-0-28
|28
|Herbs usually with leafy rosettes or fleshy hypogeous turions, rarely axillary bulblets; stems ± erect, usually not clumped, usually with dark basal scales.
|[[#key-0-34| > 34]]
|-id=key-0-34
|34
|Herbs with basal sessile or, rarely, short-stalked, leafy epigeous rosettes.
|[[#key-0-35| > 35]]
|-id=key-0-35
|35
|Stems (2–)5–40(–45) cm, simple; leaf blades 0.8-4.5 cm, margins usually subentire, rarely denticulate, subsessile; inflorescences racemes, nodding in bud.
|[[#key-0-36| > 36]]
|-id=key-0-36
|36
|Stems 10–40(–45) cm; leaf blades (1.2–)2–4.5 cm, narrowly oblong to narrowly lanceolate proximally; seed surfaces papillate.
|[[Epilobium davuricum|Epilobium davuricum]]
|-id=key-0-36
|36
|Stems (2–)5–18 cm; leaf blades 0.8–2.1 cm, obovate to narrowly elliptic proximally; seed surfaces reticulate.
|[[Epilobium arcticum|Epilobium arcticum]]
|-id=key-0-35
|35
|Stems (3–)10–85(–190) cm, ± branched; leaf blades (1–)3–10(–16) cm, margins denticulate to densely serrulate, subsessile or petiole to 10 mm; inflorescences erect racemes, panicles, or corymbs.
|[[#key-0-37| > 37]]
|-id=key-0-37
|37
|Seed coma tawny; seed surfaces papillose; leaf blade margins sharply serrulate, 30–75 teeth per side; petioles 4–10 mm; inflorescences eglandular; petals 2.5–5.5 mm, white.
|[[Epilobium coloratum|Epilobium coloratum]]
|-id=key-0-37
|37
|Seed coma white or dingy; seed surfaces ridged; leaf blade margins serrulate, (8–)15–40 teeth per side; petioles 0–5(–10) mm; inflorescences usually mixed glandular pubescent; petals 2–14 mm, pink to rose-purple or white.
|[[Epilobium ciliatum|Epilobium ciliatum]]
|-id=key-0-34
|34
|Herbs with fleshy underground turions, rarely also with bulblets in proximal or mid-cauline nodes.
|[[#key-0-38| > 38]]
|-id=key-0-38
|38
|Herbs ± eglandular; stems 7–30 cm.
|[[#key-0-39| > 39]]
|-id=key-0-39
|39
|Pedicels 5–16 mm; seeds 1.7–2.2 mm, surfaces reticulate to low papillose; stems only with hypogeous turions.
|[[Epilobium mirabile|Epilobium mirabile]]
|-id=key-0-39
|39
|Pedicels 15–38 mm; seeds 0.8–1.2 mm, surfaces papillose; stems with turions and, usually, bulblets in proximal or mid-cauline nodes.
|[[Epilobium leptocarpum|Epilobium leptocarpum]]
|-id=key-0-38
|38
|Herbs mixed glandular puberulent, at least on inflorescences; stems 2–120(–190) cm, usually more than 30 cm.
|[[#key-0-40| > 40]]
|-id=key-0-40
|40
|Seed surfaces ridged; stems (3–)10–120(–190) cm; leaf blades (1–)3–12(–16) cm; petals 2–14 mm, white, pink, or rose purple.
|[[Epilobium ciliatum|Epilobium ciliatum]]
|-id=key-0-40
|40
|Seed surfaces papillose or reticulate; stems 2–55(–60) cm; leaf blades 0.5–5.5(–6.5) cm; petals 1.6–5.5(–7) mm, white, fading or rarely pink.
|[[#key-0-41| > 41]]
|-id=key-0-41
|41
|Pedicels 8–40 mm; capsules ascending, spreading; leaves not clasping, veins inconspicuous; inflorescences ± nodding in bud.
|[[Epilobium hallianum|Epilobium hallianum]]
|-id=key-0-41
|41
|Pedicels 0–5 mm; capsules erect, appressed to stem; leaves clasping, veins conspicuous; inflorescences ± erect.
|[[Epilobium saximontanum|Epilobium saximontanum]]
|}
</div></div><!--

-->{{#Taxon:
name=Epilobium
|author=Peter C. Hoch
|authority=Linnaeus
|rank=genus
|parent rank=tribe
|synonyms=
|basionyms=
|family=Onagraceae
|distribution=North America;Mexico;West Indies;Central America;South America;Eurasia;Africa;Pacific Islands (New Zealand);Australasia
|reference=None
|publication title=Sp. Pl.
|publication year=1753
|special status=
|source xml=
|subfamily=Onagraceae subfam. Onagroideae
|tribe=Onagraceae tribe Epilobieae
|genus=Epilobium
|anther fixation=versatile
|anther orientation=erect
|anther position=episepalous
|anther size=subequal;longer
|base architecture=bulbous
|base life cycle=anthesis
|base shape=cylindrical;obconic
|blade margin shape=toothed;entire
|bract size=reduced
|bracteole presence=absent
|bud orientation=recurved;erect
|capsule architecture=sessile;pedicellate
|capsule architecture or dehiscence=splitting;splitting
|capsule course=curved;straight
|capsule dehiscence=dehiscent
|capsule shape=4-angled;terete;narrowly cylindrical;fusiform or rarely narrowly ellipsoidal
|central column condition=intact
|central column dehiscence=disintegrating
|coma duration=persistent
|coma presence=absent
|floral-tube duration=deciduous
|flower architecture=morphic;actinomorphic
|flower architecture or arrangement or growth form=solitary
|flower life cycle=flowering
|flower orientation=ascending;erect
|flower reproduction=bisexual
|fruit architecture=sessile;pedicellate
|fruit architecture or dehiscence=splitting;splitting
|fruit course=curved;straight
|fruit dehiscence=dehiscent
|fruit shape=4-angled;terete;narrowly cylindrical;fusiform or rarely narrowly ellipsoidal
|herb architecture=caulescent
|herb duration=perennial;annual
|herb growth form=suffrutescent
|inflorescence position or structure subtype=terminal
|leaf architecture or arrangement=fasciculate
|leaf arrangement=decussate;opposite
|leaf position=proximal;basal;cauline
|line prominence=raised
|line pubescence=hairy
|line shape=decurrent
|locule quantity=1
|nectary prominence=raised
|ovary architecture or structure in adjective form=4-locular
|papilla architecture=multicellular
|petal architecture or shape=emarginate
|petal coloration=usually rose-purple;white rarely cream-yellow or orange-red
|petal quantity=4
|petal shape=obovate;obcordate
|pollen fixation=basifixed
|rim shape=inflated
|ring prominence=raised
|seed quantity=2;1;numerous
|sepal coloration=lanceolate;,;flushed with red or flushed with cream;green
|sepal orientation=spreading
|sepal quantity=4
|series quantity=2
|series size=unequal
|species position=proximal
|stamen arrangement=singly
|stamen quantity=8
|stem architecture=simple;well-branched
|stem arrangement=mixed
|stem orientation=erect;ascending or decumbent
|stem pubescence=glabrous;villous;glandular-puberulent;strigillose
|stem relief=exfoliating
|stigma architecture or shape=entire
|stigma shape=clavate;capitate or deeply 4-lobed
|stigma structure in adjective form=commissural
|stipule architecture=subsessile;petiolate
|stipule presence=absent
|stolon architecture=tipped
|style orientation=erect
|surface condition or texture=dry
|surface quantity=19;18;16;15;13;12;10;9
|surface relief=papillose;finely reticulate
|surface shape=ridged
|surface size=constricted
|turion arrangement=decussate
|turion texture=fleshy
}}<!--

-->[[Category:Treatment]][[Category:Onagraceae tribe Epilobieae]]