Hardyness varies from species to species, but there are plants that are suitable even for the coldest of British gardens. Generally free from pests and diseases, the main problem we have encountered has been slugs and snails. These little beasts just adore the fresh new growth in late winter and spring. Most species, fortunately, are quite vigorous and will generally grow away from early damage. Plants most at risk are those that are freshly divided, or small young plants that have just been planted out.
Plants increase by forming new shoots from the roots.
Most species and cultivars are quite well behaved, forming quite tight clumps of growth and not spreading too far, but some species are rather more active and their running roots will send up new growths a yard or more away from the main clump. The more vigorous of the clump forming species will grow quite happily in short grass - you can mow the grass around them, but do not mow the clump. Species with running roots will also succeed in grass, though it is impossible not to cut out some of the new growth when mowing. Propagation Propagation is exceedingly simple. Seed can be used but, because of the possibilities of hybridisation, you need to either obtain the seed from a known wild source or hand pollinate plants in the garden whilst using some method of excluding pollinating insects from the flowers.