SMOOTH SOW-THISTLE

COMMON SOW-THISTLE

Sonchus oleraceus

Daisy & Dandelion Family [Asteraceae]

Flowers:
month8apr month8april month8may month8jun month8june month8jul month8july month8aug month8sep month8sept month8oct month8nov

Pappus: pappusZpossible (white)
pappus8sep pappus8sept pappus8oct pappus8nov pappus8dec

status
statusZnative
 
flower
flower8white
 
inner
inner8yellow
 
morph
morph8actino
 
petals
petalsZMany
 
stem
stem8round
 
stem
stem8hollow
 
stem
stem8milkysap stem8milkylatex
 

5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Grows up to 1.5m tall. Stout and hairless stems; leaves also hairless unless young.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Leaves have a satin sheen and are not glossy like those of Perennial Sow-thistle (aka Corn Sow-thistle). Leaves are pinnatifid have broad lobes, triangular in overall shape at the termination. They have 2 auricles at each side of the stem which are pointed (and not rounded like those of Rough sow-Thistle)


21st Sept 2010, East Lancs Rd, Walkden, Gtr M/cr. Photo: © RWD
The triangular shaped leaves have a stepped or ladder appearance.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Leaves are toothed but without spines.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Flowers are a paler yellow than those of Rough sow-Thistle, and typically have an even paler halo. Leaves are a grey-green and clasp the stem with two auricles either side of the stem.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Any hairs are not sticky (un-like those of Perennial Sow-thistle). When in seed, the flower heads bulge at the bottom to accommodate the seeds.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Flowers Dandelion-type and up to an inch across.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Florets are usually, but not always, pale yellow; paler towards the periphery (unlike those of Rough sow-Thistle where they are usually yellow)


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Like some Hawkweeds, the obverse side of the outer florets sometimes have a pale purple stripe.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Stem leaves clasp the stem with two auricles either side. This specimen has a pale-red stripe down the outer ray florets but this is not an identifying feature. The phyllaries around the flower are usually glandular hairy (as here) on Smooth Sow-thistle (on Perennial Sow-thistle they glandular hairs have a yellow tinge).


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Small leaves just at the node of the (branched) flower stalks.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Basal leaves are broad and deeply cut with triangular lobes, ending in a terminating triangle. Leaves are toothed but without spines.


3rd April 2009, Lancaster Canal. Photo: © RWD
It may look like this specimen is growing flat along the ground displaying an excellent basal leaf formation, but it is actually on a vertical stone wall Jackson! The flower stems are testament to at least one part knowing which way is up, which is more than can be said for those leaves growing downwards!


3rd April 2009, Lancaster Canal. Photo: © RWD
Note the typical large triangular(ish) end-lobe and the nearly opposite lobes of equal length on the leaf rachis. Other than this, the leaves can be very variable with more pronounced teeth, etc.


5th Sept 2010, Leeds & L/pool canal, Appley Bridge. Photo: © RWD
Lower leaves usually deeply lobed with a triangular termination.


5th Sept 2010, Leeds & L/pool canal, Wigan. Photo: © RWD


5th Sept 2010, Leeds & L/pool canal, Wigan. Photo: © RWD
The pappus and the seeds. The seeds, at 2.5-3.75mm, are slightly longer than the 2-3mm of those of Prickly Sow-Thistle. They also are supposed to have approximately 8 to 12 ribs on the seeds, which they might well have (your Author did not know this fact when he took the photograph, so never counted them all the way around the seed).


Hybridizes with : Prickly Sow-Thistle (Sonchus asper) to produce Sonchus asper × glaucescens.

Some similarities to : Prickly Sow-Thistle, Prickly Lettuce and Great Lettuce

Superficial resemblance to : Perennial Sow-thistle

The sap, contained in numerous channels, is milky.

It is also and confusingly called 'Milk Thistle', but true Milk Thistle (Silybum marianum) is a thistle with marbled leaves and a purple thistle-like flower head.

The name Sonchus is derived from the Greek for 'hollow', the Sow-thistles have hollow stems.


  Sonchus oleraceus  ⇐ Global Aspect ⇒ Asteraceae  

Distribution
 family8Daisy & Dandelion family8Asteraceae

 BSBI maps
genus8Sonchus
Sonchus
(Sow-Thistles)

SMOOTH SOW-THISTLE

COMMON SOW-THISTLE

Sonchus oleraceus

Daisy & Dandelion Family [Asteraceae]

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