Water prickly sowthistle regularly, especially during dry periods, ensuring the soil remains consistently moist but not waterlogged. Allow the top layer of soil to dry slightly between waterings to prevent root rot.

In very hot weather, more frequent watering may be necessary to maintain optimal soil moisture.

Pruning prickly sowthistle is primarily focused on managing its spread and removing spent flower stalks. Cut back stems after flowering to prevent unwanted seed production.

Remove any dead or damaged foliage to maintain plant health and appearance. This also encourages bushier growth.

Prickly sowthistle readily self-seeds, making propagation simple. Seeds can be collected from mature plants and sown directly into the garden in autumn or early spring.

Alternatively, sow seeds indoors a few weeks before the last expected frost. Division of established clumps is also possible.

Repotting is not typically necessary for prickly sowthistle as it is often grown as an annual or self-seeding perennial and can spread aggressively. If grown in containers and it becomes root-bound, repot in spring to a slightly larger container with fresh, well-draining potting mix.