Smooth Sow-thistle
Smooth Sow-thistle - Sonchus oleraceus
Short to tall greyish plant. Upper leaves clasp the stem with triangular, leaves with pointed basal lobes. Flowerheads pale yellow 20 to 25 mm, borne in lax clusters.
Prickly Sow-thistle
Auricles of stem-leaves pointed. Achenes transversely rugose. Leaves deeply pinnately lobed, but can be very similar to S asper
Photograph of stem and leaves, showing auricles
Bare and waste ground, roadsides. A weed of cultivation.
May to November.
Annual.
Very common throughout Britain except for parts of the Scottish Highlands.
Very common in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 530 of the 617 tetrads.
Alan Semper
Harby roadside
18 April 2014
David Nicholls
Martinshaw Wood
05 July 2012
leaf with pointed basal lobes Church Walk Sapcote SP 4894 9320 (taken 11.10.2008).JPG)
Graham Calow
Sapcote
11 October 2008
Alan Semper
Harby churchyard
28 May 2012
Ken Charity
Anstey garden at LE7 7TE
29 May 2018
 Church Walk Sapcote SP 4894 9320 (taken 11.10.2008).JPG)
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Cystiphora sonchi
These blisters on sowthistle leaves are galls caused by the midge Cystiphora sonchi. They are most commonly found on Smooth Sow-thistle but may also be found on Prickly and Perennial Sow-thistle.
Uroleucon sonchi
Uroleucon sonchi is a large, dark brownish aphid with a glossy shine. It is associated with Sow-thistle species.
Chromatomyia horticola/syngenesiae agg.
Chromatomyia syngenesiae and Chromatomyia horticola are leaf mining Agromyzid flies which form mines on a large number of plant species including Smooth Sow-thistle, these mines are indistinguishable from each other on certain hosts. They are treated as an aggregate, previously called Chromatomyia atricornis.
Liriomyza sonchi
The larvae of the fly Liriomyza sonchi form large upper surface blotch mines on the leaves of sow-thistle species. Secondary feeding corridors are often present. Scattered frass can be seen in the mine. Several larvae may feed together in the mine.
Liriomyza taraxaci
The larva of the Agromyzid fly Liriomyza taraxaci mines the leaves of Dandelion, Sow-thistle species and Autumn Hawkbit. They form small, irregular, elongated blotch mines with little frass inside.