Grey alder, silver birch, yellow bedstraw, raspberry, mugwort and Myrica gale are examples of species in this zone which do not grow further north or higher up.
From the en.wikipedia.org
Agrimony's small yellow flowers, and the bright little flowers of lady's bedstraw.
From the thisisbristol.co.uk
Buy seed mixes that contain ox-eye daisies, yarrow, harebells, birdsfoot trefoil, cowslips, lady's bedstraw, betony, yellow rattle and others for waving drifts of colour.