Although it's true that those well-meaning chaps on the allotment have occasionally referred to my lovely 'crop of slugs', I am not writing about setting up a…
Give them good soil drainage which is essential. They will prefer full sun and will performs best in cool regions. They will spread by underground runners; it is easily divided in the spring. You can cut back after flowering to encourage bushiness.
Seeds need light for germination. Division in spring. Cut back after flowering to encourage bushiness.