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annual sow-thistle, common sow-thistle, laiteron, sow thistle

laiteron, sow-thistle

Habit Annuals or biennials, 10–140(–200) cm. Annuals, biennials, or perennials [shrubs], 3–350+ cm; taprooted, rhizomatous, or stoloniferous.

bases soft to hard, herbaceous, often hollow.

erect, branched distally or throughout, usually glabrous, sometimes stipitate-glandular (mostly distally).


blades of mid cauline spatulate or oblong to obovate or lanceolate, 6–35 × 1–15 cm, bases auriculate, auricles deltate to lanceolate, ± straight, acute, margins usually pinnately (often runcinately) lobed, lobes ± deltate to lanceolate, not constricted at bases, terminals usually larger than laterals, entire or dentate.

basal and cauline or mostly cauline;

basal usually petiolate (petioles usually winged), cauline often sessile;

blades mostly oblong, oblanceolate, or lanceolate, (bases often auriculate) margins usually 1(–2)-pinnately lobed, ultimate margins usually dentate (teeth often ± prickly), sometimes entire.


usually glabrous, sometimes stipitate-glandular.

not notably dilated distally, usually ± bracteolate, glabrous or stipitate-glandular and/or tomentose.


9–13+ mm.

campanulate to urceolate, 5–15+ mm diam.


flat to convex, ± pitted, glabrous, epaleate.



corollas yellow to orange (not deliquescent; anthers yellowish to brownish apically).


ligules ± equaling tubes.


usually glabrous, sometimes tomentose and/or stipitate-glandular.

27–50 in 3–5+ series, unequal, green, deltate to lanceolate or linear, margins sometimes narrowly scarious (sometimes ciliate), apices acute (faces glabrous or stipitate- to setose-glandular).




borne in corymbiform to subumbelliform arrays.


dark brown, mostly oblanceoloid, 2.5–3.5+ mm, ribs 2–4 on each face, faces transversely rugulose or tuberculate across and between ribs;

pappi 5–8 mm.

stramineous or reddish to dark brown, ± compressed, mostly oblong or oblanceoloid to ellipsoid, beaks 0, ribs usually 2–4(–5+) on each face, faces sometimes transversely rugulose or tuberculate, glabrous;

pappi tardily falling or persistent, of 80–100+, white, smooth or barbellulate bristles (some flattened, ± setiform scales), outer usually distinct in ± 1 series, inner basally coherent or connate, in 2–3+ series.


= 9.


= 32, 36.

Sonchus oleraceus


Phenology Flowering (Apr–)Jul–Oct (year-round in south).
Habitat Disturbed sites, gardens, roadsides, along streams
Elevation 0–2000 m (0–6600 ft)
from FNA
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; SPM; Greenland; Europe [Introduced in North America; introduced also in Mexico, West Indies, Bahamas, Central America, South America, Africa, Asia, Pacific Islands (New Zealand), Australia]
[WildflowerSearch map]
[BONAP county map]
from USDA
Europe (Mediterranean); w Asia; n Africa; Atlantic Islands [Introduced in North America; some species introduced nearly worldwide]
[BONAP county map]

Species 50–60+ (5 in the flora).

Sonchus species are herbs in North America; some are sometimes woody at bases.

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

1. Leaf base auricles often recurved or curled, rounded; ligules shorter than tubes; cypselae strongly compressed, ± winged, ribs 3 on each face, faces not rugulose or tuberculate; annuals or biennials
S. asper
1. Leaf base auricles usually straight, sometimes curved, obtuse or acute; ligules shorter or longer than tubes; cypselae weakly compressed, ribs 2–5+ on each face, faces transversely rugulose or tuberculate; annuals, biennials, or perennials
→ 2
2. Annuals or biennials; stem bases soft to hard, herbaceous, often hollow
→ 3
2. Perennials; stem bases hard, sometimes ± woody
→ 4
3. Leaf blade lobes ± deltate to lanceolate (not constricted at bases), the terminal usually larger than laterals; ligules ± equaling tubes; widespread
S. oleraceus
3. Leaf blade lobes ± rhombic to lanceolate (constricted at bases) or ± linear, the terminal ± equaling laterals; ligules longer than tubes; occasional, mostly historic on ballast
S. tenerrimus
4. Cauline leaf base auricles rounded; cypselae dark brown, 2.5–3.5 mm; pappi 8–14 mm; widespread
S. arvensis
4. Cauline leaf base auricles acute; cypselae stramineous, 3.5–4 mm; pappi 7–9 mm; Ontario
S. palustris
Source FNA vol. 19, p. 275. FNA vol. 19, p. 273. Author: Philip E. Hyatt.
Parent taxa Asteraceae > tribe Cichorieae > Sonchus Asteraceae > tribe Cichorieae
Sibling taxa
S. arvensis, S. asper, S. palustris, S. tenerrimus
Subordinate taxa
S. arvensis, S. asper, S. oleraceus, S. palustris, S. tenerrimus
Name authority Linnaeus: Sp. Pl. 2: 794. (1753) Linnaeus: Sp. Pl. 2: 793. (1753): Gen. Pl. ed. 5, 347. (1754)
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