Sonchus asper
Sonchus arvensis
laiteron rude, prickly sow-thistle, sharp-fringe sow thistle, spiny sow-thistle, spiny-leaf sow-thistle
field sow-thistle, laiteron des champs, perennial sow-thistle
bases soft, herbaceous, hollow.
bases hard, sometimes ± woody.
blades of mid cauline spatulate or oblong to obovate or lanceolate, 6–30 × 1–15 cm, bases auriculate, auricles often recurved or curled, rounded, margins often pinnately lobed, lobes ± deltate (not constricted at bases), terminals usually larger than laterals, usually prickly-dentate.
blades of mid cauline oblong to lanceolate, (3–)6–40 × 2–15 cm, bases auriculate, auricles straight or curved, rounded, margins usually pinnately lobed, lobes ± deltate, not constricted at bases, terminals usually larger than laterals, dentate or entire.
usually stipitate-glandular, sometimes glabrous.
sessile- or stipitate-glandular.
9–13+ mm.
10–17+ mm.
ligules mostly shorter than tubes.
ligules ± equaling tubes.
usually stipitate-glandular.
sessile- or stipitate-glandular.
stramineous to reddish brown, mostly ellipsoid, strongly compressed, ± winged, 2–3 mm, ribs 3(–5) on each face, faces smooth across and between ribs;
pappi 6–9 mm.
dark brown, oblanceoloid to ellipsoid, 2.5–3.5 mm, ribs 4–5(+) on each face, faces transversely rugulose to tuberculate across and between ribs;
pappi 8–14 mm.
= 18.
= 36, 54.
Sonchus asper
Sonchus arvensis
L. Boulos (1973) distinguished subsp. asper (annuals with leaves mostly cauline, cypselae margins little or not at all curved and/or ciliate, and one pair of chromosomes with small satellites) from subsp. glaucescens (biennials with leaves mostly in rosettes, leaves mostly stiffer and more prickly than in subsp. asper, cypselae with curved, ciliate margins, and two pairs of chromosomes with large satellites) and noted that the two subspecies are morphologically rather difficult to distinguish if the specimen in hand lacks the rootstock or stem base.
According to H. N. Barber (1941), crosses between Sonchus asper and S. oleraceus resulted in sterile hybrids.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies 2 (2 in the flora).
Sonchus arvensis is introduced in temperate regions of all continents. Plants of the species prefer relatively cooler, moister climates and are more abundant in the northern part of North America.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Peduncles stipitate-glandular; phyllaries stipitate- glandular | subsp. arvensis |
1. Peduncles sessile-glandular; phyllaries usually sessile-glandular, rarely tomentose | subsp. uliginosus |
- Local floras:
BC, 
OR, 
WA - Local Web sites:
CalFlora, CalPhotos, 
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria, 
SW CO Wildflowers 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
- Local floras: BC, CA, OR, WA
- Local Web sites: CalFlora, CalPhotos, Flora NW, Go Botany, IL Wildflowers, KS Wildflowers, MD Biodiversity, MI Flora, MN Wildflowers, MO Plants, PNW Herbaria, Turner Photog.
- WildflowerSearch
- iNaturalist (observations)
- USDA Plants Database
- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
