The slender thistle (Carduus tenuiflorus) can possibly be a difficult thistle to identify because it looks, at first glance, like the very common creeping thistle. However, it does not grow in the same dense, spreading clusters as the creeping thistle and is a tall, slender (as the name implies) plant that can reach two metres tall on occasions. The flower heads are a paler pink and come in large clusters at the top of the stem. Overall, the plant is very spiny.
This is an uncommon species in Britain and is found mainly near the coast, especially on cliffs in the south of England. There is a lot of it on the cliff tops near St Adhelm's Head and it also occurs on the Purbeck Ridge at Ridgeway Hill. The car park at Studland is full of it! Where it does occur it is usually well established and as iIt does not seem to have a medicinal uses it is considered something of weed; but then so are most thistles.
It has several common names around the world including the shore thistle and the sheep thistle which rather reflect the habitats it tends to favour. It is an untidy, rather nondescript plant that flowers from June to August. It is at its 'best' in July but really this is a plant that is never really at its best!