Mine is in a large pot and I know that these plants like to be pot bound, this year however was not a very good year owing to our cold winter not ending until about May!! You have to watch the crafty snails and slugs which will happily munch on the new shoots when no-one is looking. I also leave the leaves to die back on their own and have always left mine outside during winter, but I live down in the SE!

I've always found they do much better in the open ground - if yours is a hardy variety, it should be okay and should produce more flowers next year. If you think its a tender one, repot and keep under shelter for winter.

Mine is in the ground and Im further north than you, but it is in a south facing aspect, I just leave it to die back naturally and the dead stems just pull out easily in the spring when Im tidying up. Ive noticed that you only get one new flower each year! well I did !! this year I had about five I think.

I had one that was pot bound. Most of it went squishy with the frost last winter. I found 2 bits that looked alive and planted them up in a decent sized pot, shared with an orange perlargonium. They have both grown well and bloomed. I think they are a plant that does a different performance for their growers. I have seen them in massed flower in some people's gardens. Will not flower in the ground for me....tried several times.