Know Your Thistles
The thistle, Scotland's national flower, is a powerful symbol of pride, resilience, and heritage. Known for its striking beauty and hardy nature, the thistle embodies the strength and determination of the Scottish people.
Despite being known as a weed the seeds of the thistle are a very valuable wildlife resource. The seeds are attractive to many seed eating birds such as goldfinches.
Thistles provide food for many insect species, most notably the painted lady butterfly, whose caterpillars feed on its leaves. At the end of the summer, the dry stems become a refuge for overwintering insects and their larvae, to protect from the frost. The flowers provide nectar and pollen for pollinating insects, such as bees, butterflies, moths and hover flies, which enriches the rest of the habitat around them.
In Scotland there are several different thistle species, but the main three species encountered on farms are as follows.
Creeping Thistle, Cirsium arvense.
Often seen in high densities in agricultural fields and roadsides, it is widespread and troublesome It is a persistent weed, which overwinters as a root and sprouts again in spring. Rooting depth is usually 1-2cms. In natural, undisturbed growing conditions, the thistle develops into a biennial plant. If disturbed in its development by agricultural interference, such as cutting and hoeing, it reacts by intensified production of roots and shoots. This thistle does not spread by seed but by fragments of rhizome which can remain dormant in the soil for years and then appear when there is a gap in the sward. This makes it a problem in rotations at times. A small cutting can spread into a 20m patch in just two years. Creeping thistles are not palatable to stock, with stock generally not grazing close to them, which reduces grass utilisation.
Spear Thistle, Cirsium vulgare.
A widespread and common biennial thistle, producing a tap root. The spear thistle can be found on disturbed and cultivated ground throughout Scotland, with seeds readily germinating in mild conditions This thistle spreads only by seed dispersal by wind and therefore cutting before seeding and mechanical disturbance that damages the base leaves are an effective way to control its spread if it becomes a problem.
Marsh Thistle, Cirsium palustre.
Is a beautiful and hardy plant species commonly found in marshy or damp habitats, such as bogs, fens, and wet meadows. It is a biennial plant that grows up to 150 cm tall, producing large, spiny leaves and bright, showy flowers. In Scotland this thistle tends not to spread across a field as it is confined to the wet areas. It therefore doesn’t usually need any control. Like other thistles the Marsh thistle has a high biodiversity value being important for a variety of pollinators, including bees, butterflies, and moths.
Tips for Managing Thistles
Timing is critical in managing thistles. It is critical that you avoid them flowering and spreading more viable seeds. Managing thistles in grassland is likely to take a few years to control all thistles.
- Prevent seeding by cutting/topping – timing is key. Cut or top thistles before the flower bud opens. It is likely that you will have to repeat topping to prevent seeds from forming.
- Effectively graze livestock. Consider mob grazing, to keep grass swards dense to compete with thistle seedlings.
- Carry out regular soil analysis and monitor soil health to correct deficiencies in nutrients and pH to ensure optimum conditions for healthy grass growth.
- Prevent livestock poaching around water troughs and feeding areas, which provide conditions for thistles to establish.
- Avoid broad-spectrum herbicides that can harm beneficial plants. Instead look to spot treat and apply herbicides selectively.
Helen Bibby, Senior Consultant, Helen.Bibby@sac.co.uk
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Posted by Unearthed News on 15/09/2025
