Here's a real 'must' for the herbaceous border, rock garden or patio container. Lime-green to white flower buds burst open to reveal large 4cm (1½in) blooms, which are as pure as snow.
Sow from February to June on the surface of a good seed compost just covering the seed with a thin layer of compost or vermiculite. Germination takes 14-30 days at 18-20C (65-70F). Don't exclude light, sealing in a polythene bag after sowing is helpful.
When large enough to handle transplant the seedlings to boxes or 7.5cm (3in) pots, and grow on in cooler conditions. When well grown gradually acclimatise to outdoor conditions and plant out in late spring after all risk of frost has passed 30cm (12in) apart in full sun and well drained soil.