Strictly speaking the Apple Mint and the Round-leaved Mint are very closely related and anatomically marginally different flowers (not to mention False Apple Mint and the other hybrids which bedevil the identification of mints). Here we will just identify the main features of this group of mints.

The Apple-scented Mint is the mint of mint sauce, the English invention used (in the view of some) to mistreat cooked meat. (The author is a vegetarian, so he doesn't understand these things - Ed.). It is a native or European introduced perennial (depending on which book you read) with a minty smell (minty apple?), found in ditches, verges, waste places and gardens, from which it also escapes. It is found in England, Wales and Ireland, and is uncommon, but not unheard-of, elsewhere. The main features which distinguish it from the other common types of mint are broad rounded and wrinkled leaves, and pinkish flowers in spikes.

Flower: Tiny pale pink four-petalled flowers arranged in spikes
Leaves: Unstalked hairy rounded oval, slightly pointed and toothed, with conspicuous wrinkles. Older leaves are downy underneath.
Habitat: Ditches, verges, wasteland, gardens
Height to about 60 cm
Typically flowering: August-September