Persicaria polymorpha (Polygonum polymorpha) – A non-invasive clumping form (also doesn’t self-seed) of Giant Fleeceflower which bears large white plumes from June through to September. It forms a large clump with bamboo-like stems and deep green tapered leaves. Great in combination with Miscanthus ‘Morning Light’. Grows 4-6′ high and wide. Hardy to zone 4.
Polemonium reptans ‘Touch of Class’ – I’ll be the first to admit that the pale pink buds do open to soft blue flowers, but at a distance they almost look white. However, this sport of ‘Stairway to Heaven’ has spectacular green compound foliage with intricate white edges. It flowers from late spring into summer. Prefers partial shade. Grows 14″ high by 18″ wide. Hardy to zone 3.
Lysinachia ephemerum – Willow-Leaved Loosestrife is another non-invasive perennial with elegant tapered spires of tiny white flowers (with mauve veins) borne from mid to late summer. The thin willow-like greyish-green leaves add to the overall appeal and work well in an Alba garden. The blooms make excellent cut flowers. Grows 3-4′ high by 18-24″ wide. Hardy to zone 5.
Acanthus mollis ‘Whitewater’ – A hard to find variegated Bear’s Breeches with deeply cut oak-like leaves of green with irregular patches of cream and white. Mature plants produce 4′ tall flower stalks with pink stems and pale rose and cream blooms from June to July. It has better vigor than ‘Tasmanian Angel’ and prefers part to full shade. Grows 3′ high by 4′ wide. Hardy to zone 7.
Veronica longifolia ‘Charlotte’ – The perfect combination of intricate cream variegation and stately spires of pristine white flowers. ‘Charlotte’ blooms from early to late summer (with deadheading) and will definitely attract the butterflies. It is compact, mildew resistant and prefers a full sun exposure. Grows 24-30″ high by 18-24″ wide. Hardy to zone 4.