Hybridizes with : Marsh Thistle (Cirsium palustre) to produce (Cirsium × wankelii).

Uniquely identifiable characteristics: Amongst other thistles, Melancholy Thistle has straight, grooved stalks becoming whiter towards the often solitary upright flower. The stems are otherwise without prickles. The leaves look similar to those of sow-thistles in that there are no sharp spines and even the slightly toothed edges are not sharp enough to pierce skin, and are a cottony white beneath.

The 'heterophyllum' part of its binomial name is a reflection on its leaves, which are of two different kinds, being reduced, not winged on the upper part of the plant.

Uncommonly for a thistle any spines are very short and soft, and appear only on the much larger lower leaves. It is native and grows on grassland (as here), on scrub, in open woodland, by streams - usually in hilly countryside. It is locally common occurring from Derbyshire north to the tip of Scotland and beyond, with just a few locations in North & Mid-Wales. It is totally absent in much of Southern England south of Derbyshire.