Evergreen perennials
The plants listed are evergreen, that is they keep some foliage over the winter months.
Perennials:
Achillea
Alchemilla
Anthemis
Bergenia
Dianthus
Dierama
Epimedium (some)
Erysimum
Euphorbia (most)
Geranium (some)
Geum
Helleborus
Heuchera
Heucherella
Kniphofia (some)
Lavandula
Liriope
Pulmonaria
Sisyrinchium
Stachys
Ferns:
Asplenium
Blechnum
Dryopteris erythrosora
Polystichum setiferum
Grasses:
Carex