This is one of the commonest plants of the wayside and it flowers throughout the summer and sometimes well into the winter. If the winter has been mild, I would expect to find one or two in flower for the Wild Flower Society's first week hunt in March. The flowers are usually white but can be pink (var. rosea).

Achillea millefolium can be the host to a nationally rare parasitic plant: Orobanche purpurea (Yarrow Broomrape) which seems to require very specific habitat conditions unlike its host which is found throughout the whole of the British Isles.