BASF Agricultural Solutions UK

Smooth sow-thistle

(sonchus oleraceus)

Young Plant

The cotyledons are oval with very short stalks. The first leaf ends in prickles and is oval but cut almost square across to the stalk. It is edged with teeth pointing towards the centre of the plant.

Mature Plant

The stem is thick, smooth, hollow and much branched. The green shiny leaves are oblong in outline and lobed, with a triangular lobe at the end. They are slightly prickly and the lower leaves have a short stalk while the upper clasp the stem.


The lemon yellow flowerheads are 20-25mm across and grow in loose clusters. The outer ray florets are purplish underneath. The buds are cylindrical but the base of the flower is flask shaped, becoming more pronounced as the flowerhead dies.

Height 120cm

Smooth sow-thistle Profile

Key feature- Leaves are glossy and softly prickly with a wide triangular lobe at the base clasping the stem
- A single taproot
- Flowers are lemon yellow
Number of seeds produced per plantUp to 100,000
Seed shedMay-October
Germination periodMarch-July and September to November
Germination depth2cm
Primary dormancyLow
Does it have a secondary dormancy?Yes
Seed longevity>5 years
Factor promoting germinationLight
Rate of seed decline with cultivationsHigh
LifecyclePlants which germinate in autumn overwinter as rosettes, producing flowers in May/june; plants germinating in spring flower in June. The latter can set seed in 10 weeks. Prickly sow-thistle only reproduces by seed and is distributed by wind
Geographical LocationWidespread in England and Wales
Soil TypeNitrogen rich loams or nutrient rich sandy and stoney soils which are not too dry
ImpactIncreasing found in arable rotations particularly in winter crops. Autumn germinating plants can overwinter as rosettes and flower in May, spring germinating plants flower in June
5% yield loss from 50 plants per m2
Resistance riskNo resistance in the UK but resistance to a wide range of herbicides in Austrailia.
Spray application

Spray application

Find out what our expert, Tom Robinson advises when it comes to spray application.

Cultivation principles

Cultivation principles

Philip Wright talks on cultivation principles.

Chemical control

Chemical control

Stuart Kevis and Iain Ford talk on chemical control.



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