Noting Taraxacum diversity per Bjork et al. using the diagnostic criteria outlined in Overlooked diversity in exotic Taraxacum in British Columbia, Canada, text is taken from there. Several species groups are found in the Metro Vancouver area, and this summer I'm going to try do document them on my account, with this as a reference I can go back to for ID'ing.

Of the seven sections found in BC, four are (per the study) found in Metro Vancouver.

Section Celtica

Plants mostly small or medium sized, usually only sparsely arachnoid or glabrate; leaves prostrate to ascending, seldom erect, in most species dark, often bluish green, more or less flat, not or weakly rugose, lobes entire or dentate, if dentate then usually finely so, lobes usually not hamate, terminal lobe ampliate or not, most species not heterophyllous; involucres small to medium sized; outer bracts mostly 7–12 mm long, mostly not distinctly graduated, erect, spreading or recurved, not reflexed, outline deltate-ovate to deltate-lanceolate, tapering to a minutely rounded apex, often densely glaucous, abaxially dark, drying dark and glossy as if varnished, sometimes slightly translucent when dry, never corniculate; inner bracts dark, often densely glaucous, apices never corniculate; ligules yellow, outer ones (our species) striped abaxially; pollen abundant or (often) absent or scarce; stigmas upon drying yellow, sordid, or blackish; cypselae light to medium brown or olive brown, mostly spinulose distally or sometimes merely tuberculate, cone concolorous with the body, narrowly conical, mostly 0.4–0.7 mm long.

Species of section Celtica are not aggressively weedy, shunning recently disturbed sites or over-nitrified soils (Quentin Cronk, personal communication, 2014). They occur mostly in moist, mossy, often partly shaded lawns or in gardens and landscaping. In British Columbia, the frequency and species diversity of the sections decreases precipitously with increasing distance from marine shores (Fig. 7). In the greater Vancouver metropolitan area, I observed most of the species of this section on the campus of The University of British Columbia. In the suburbs south of Vancouver (Delta, Richmond, western Surrey), I found few examples of this section, and none eastward along the Lower Fraser River through the suburbs of eastern Surrey, Chilliwack, Langley, or Abbotsford. They also occur on southern Vancouver Island, in and near Victoria, north along the Saanich Peninsula and on the Gulf Islands.

Section Erythrosperma (H.Lindb.)

Plants mostly small, often sparsely arachnoid; leaves prostrate to ascending, in most species dull or dark green, more or less flat, not or scarcely rugose, lateral lobes linear to deltate or hamate, often secondarily lobed, terminal lobe deltate, sagittate, or trilobate, usually not ampliate, leaf outline mostly oblanceolate to narrowly elliptic; involucres mostly small, sometimes medium sized; outer bracts mostly 5–10 mm long, mostly not distinctly graduated, mostly recurved, obovate to oblanceolate, abruptly rounded to a minutely rounded or truncate apex, opaque, pale to medium green and usually with a pinkish or purplish blush on the adaxial face, sometimes glaucous, many or all minutely corniculate; inner bracts mostly medium green, sometimes glaucous, apices sometimes corniculate; ligules medium yellow, outer ones striped grey, purple, or brown; pollen abundant or absent; stigmas on drying yellow, sordid, or blackish; cypselae light to darkish brown, pinkish brown, red-brown, purplish brown, or olive brown, spinulose distally, cone concolorous with the body or the apex paler, almost cylindric with little taper, mostly 0.6–1 mm long.

Section Erythrosperma has long been known to be widespread and weedy in North America, where nearly always they have been misnamed T. erythrospermum or T. laevigatum. Not all specimens named by those two species belong to this section, however, as a variety of unrelated North American weedy Taraxacum species with small capitula and small stature has been assumed to be of this affinity, especially species of sections Borea, Celtica, and the T. fulvicarpum group. Occasionally, species of section Erythrosperma have been identified as native species, as keys in old North American floras generally segregated native from exotic Taraxacum species by the presence/absence of horns on the bracts.

Section Hamata H.Øllg.

Plants mostly medium to large sized, usually only sparsely arachnoid or glabrate; leaves prostrate to ascending or erect, in most species medium olive green, more or less flat, not rugose, lobes entire or dentate, if dentate then usually finely so, lobes hamate, terminal lobe ampliate or not, most species not heterophyllous; involucres medium sized; outer bracts mostly 8–12 mm long, spreading or recurved, mostly not distinctly graduated, deltate-lanceolate, abruptly narrowing or sometimes tapering to a minutely rounded apex, often densely glaucous, abaxially dark, drying dark and glossy, as if varnished, sometimes slightly translucent when dry, never corniculate; inner bracts dark, often densely glaucous, apices never corniculate; ligules yellow (rarely orangish yellow), outer ones striped grey, brown or purplish abaxially; pollen abundant; stigmas upon drying yellow or sordid; cypselae light to medium brown or olive brown, mostly spinulose distally or sometimes merely tuberculate, cone concolorous with the body, narrowly conical, mostly 0.4–0.7 mm long.

Many species can be recognized as belonging to section Hamata at a glance by their usually four (per side) hamate lateral leaf lobes and nearly flat, somewhat olive-green leaves. Their outer bracts are also characteristic, usually intermediate in shape between the slender, lanceolate outer bracts of most species in sections Celtica and Naevosa and the more oblong outer bracts of most species of section Taraxacum. However, some species of section Hamata have characteristics that may lead to errors in identification. For example, Taraxacum boekmanii Borgv. and Taraxacum prionum Hagend., Soest & Zevenb. could be misidentified as species of section Celtica by their darker green leaves and non-hamate lateral lobes. However, both of those species have a broader outer bract shape than nearly all species of section Celtica, and unlike many species of that section, these species bear abundant pollen. Taraxacum atactum Sahlin & Soest and Taraxacum sahlinianum Dudman & A.J.Richards, which also have lateral lobes not or scarcely hamate, may appear similar to species of section Taraxacum in that their leaves are more textured than is usual in section Hamata. Again, examining the outer bracts should make identification as section Hamata easy with those two species.

Section Naevosa M.P.Christ.

Plants small to large, mostly puberulent or hirsutulous and often also arachnoid; leaves prostrate to erect, in most species dark green, more or less flat, smooth or rugulose, lobes entire or dentate, if dentate then usually finely so, lobes usually not hamate, terminal lobe ampliate or not, most species not heterophyllous; involucres small to medium sized; outer bracts mostly 7–12 mm long, mostly not distinctly graduated, erect, spreading, recurved, or reflexed, deltate-lanceolate to oblong-lanceolate, tapering to an acute or minutely rounded apex, often densely glaucous, abaxially dark, drying dark and glossy as if varnished, sometimes slightly translucent when dry, never corniculate; inner bracts dark, often densely glaucous, apices never corniculate; ligules yellow, outer ones striped abaxially; pollen abundant or (often) absent or scarce; stigmas upon drying yellow, sordid, or blackish; cypselae light to medium brown or olive brown, spinulose distally or sometimes merely tuberculate or even smooth, cone narrowly conical, mostly 0.5–0.9 mm long.

All three species of section Naevosa so far known from British Columbia could be mistaken for section Celtica, especially T. duplidentifrons, which has often been placed in that section. These species all have slender, lanceolate outer bracts and dark colouration as is generally true of section Celtica. However, unlike species of section Celtica, all three of these species have short, crisped hairs on the leaf adaxial surface and (or) a relatively firm leaf texture.

Section Taraxacum F.H.Wigg.

Plants mostly medium sized to large, mostly arachnoid, sometimes also puberulent; leaves prostrate to erect, light to medium or sometimes dark green, mostly crisped, usually with at least slight undulations at the internodes and some adaxial curvature, smooth or (more often) rugulose, lobes entire or dentate, if dentate then usually finely so, sometimes secondarily lobed, lobes usually not hamate, terminal lobe ampliate or not, some species heterophyllous; involucres medium sized to large; outer bracts mostly 10–14 mm long, not distinctly graduated, mostly recurved or reflexed, mostly oblong to oblong-lanceolate, usually abruptly contracted to a rounded apex, usually not glaucous, abaxially usually olive green or greyish green, not changing much in colour upon drying, opaque when dry, never corniculate; inner bracts mostly olive green or greyish green, sometimes glaucous, apices never corniculate; ligules yellow or sometimes orangish, outer ones striped abaxially; pollen abundant or (rarely) absent; stigmas upon drying yellow, sordid, or blackish; cypselae light to medium brown or olive brown, spinulose distally, cone narrowly conical, mostly 0.4–0.8 mm long.

Section Taraxacum includes more species than any other section of the genus. The centre of diversity of section Taraxacum occurs in central Europe (den Nijs et al. 1990), although apparently all species of this section so far known from British Columbia originated in or are also introduced in northern Europe. In British Columbia, species of section Taraxacum are most abundant in temperate climates, but the section is widespread (Fig. 19). In boreal climates, species of this section are less common than species of section Borea and Boreigena.

The T. fulvicarpum group unranked

Plants small to medium sized, glabrate; leaves prostrate to weakly ascending, medium to dark green, flat or slightly crisped, smooth, usually complexly lobed, not or somewhat heterophyllous, lobes mostly dentate and sometimes also secondarily lobed, lateral lobes hamate, terminal lobe often ampliate; involucres small to medium sized; outer bracts about 9 mm long, not distinctly graduated, ascending to (mostly) recurved, not reflexed, deltate-ovate, tapering to a minutely rounded apex, medium olive green, more or less glaucous, corniculate; inner bracts medium to dark olive green, more or less glaucous, at apex calloused or minutely corniculate; ligules yellow, outer ones striped red-brown abaxially; pollen present (ours) or absent; stigmas sordid upon drying; cypselae light pink-brown, spinulose distally, cone broadly conical, ca. 0.5–0.7 mm long.

Taraxacum fulvicarpum is possibly the most abundant and widespread exotic Taraxacum in coastal British Columbia, at least in the areas studied (mostly urban Vancouver and southeastern Vancouver Island). It is so far unknown from elsewhere in North America, but it should be sought in both Atlantic and Pacific coastal regions.

https://cdnsciencepub.com/doi/full/10.1139/cjb-2018-0094#.XMtI6jBKjIV