Good, neat, floriferous and mildew-free. As the Fergusons said (somewhat enigmatically), "First find your clone"....
purple/mauve
ALLIUM SCHUBERTII
The most dramatic large purple flower heads (good dried) May-Jul, 50cm. Usefully enjoys the protection of deciduous...
ALLIUM SENESCENS subsp.GLAUCUM
Lovely leaves in grey swirls still good at anthesis, mauve flowers Jul-Sep, 25cm. Easy, good for butterflies and bees.
ANEMONE NEMOROSA ‘BOWLES’S PURPLE’
Purple-backed blue flowers Mar-May, dark foliage - lovely. 15cm. Easy.
ASTER ‘COTSWOLD GEM’
A hybrid chance seedling from Aster pyrenaeus 'Lutetia' probably with an Aster amellus cultivar as the pollen parent....
ASTER AGERATOIDES ‘ASRAN’
Shapely plant with pale lilac flowers late - Sep-Nov, cut foliage no mildew, 60cm. Easy and good. Even dry shade.
BALLOTA PSEUDODICTAMNUS COMPACT FORM B&M 8119
Like a neater greyer Ballota acetabulosa and equally hardy. Woolly pale green bushette, whorls of soft purple flowers,...
BETONICA MACRANTHA ‘SUPERBA’
This is the real thing from division from an accredited plant! Large fat lilac-purple spikes of flower on a gently...
CAMPANULA ‘CAROLINE’
Lovely very large pale blue purple and amethyst-flushed flower heads May-Jul, 45cm. Cultivar of a British native plant.