Facts at a glance – Prickly Sow Thistle




Key feature ·       Leaves are glossy and have sharp prickly edges and rounded bases that clasp the stem

·       A single taproot

·       Mid yellow flowers

Number of seeds produced per plant 5,000
Seed shed May-October
Germination period: March-July and September to November
Germination depth: 5 cm
Primary dormancy Low
Does it have secondary dormancy yes
Seed longevity >5 years
Factor promoting germination light
Rate of seed decline with cultivations High


Plants 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 Location Widespread in England and Wales
Soil Type Nitrogen rich loams or nutrient rich sandy and stoney soils which are not too dry
Impact Increasing 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 risk No resistance in the UK but populations resistant to ALS herbicides in France, Norway, USA and Canada
Young plant

The cotyledons are oval and short stalked. The first true leaves are edged with backward-pointing teeth, and the overall shape that of a rounded diamond. The leaf is a dull blue green colour and the edge may be tinged with purple.


Mature Plant

The branched stem is smooth and hollow. The leaves are a glossy rich green and clasp the stem with rounded bases.



Flowerheads are pale yellow, 20-25mm across, and form loose clusters. Petals are reddish-grey beneath. The base of the flowerhead is flask -shaped, becoming more pronounced as it grows older.


Height 120cm



All species – Spreads by windblown seeds so most seed will originate from outside the arable area. Mow these areas to prevent seed development. Ensure plants are controlled where they occur. They do not like competition so ensure areas have a full vegetation cover. Avoid bare soil

Perennial – thickened roots are frost sensitive so cultivations to leave them in the surface are important, or chop and bury so they cannot emerge.


Prickly sow-thisle News