Grow it in sun, and water it when you plant it - you'll find that it comes up very late the following year, so mark where it is in the autumn.

I have 2 of these in pots, one cream & one purple ... after flowering really well all summer they just die back & disappear under the surface of the compost.
I leave them out all winter close to the greenhouse so a little protected & they emerge again about now with little purple shoots & go on to flower again!
Hope that's useful to you ... I may just be lucky but they've done it for years now!

Another one of the self seeders in my garden, all except the pink one which for some reason does nothing but grow and flower.

You are lucky, Ob.....wish they'd seed themselves here!

If they do not self seed then they are very easy to grow from seed sown fresh from the plant.

OK, thanks. :-)