Posted: 08/07/2014 at 17:01
Hi , you dont have to do anything special for dahlias, unless they are show plants . I planted one of my larger dahlias quite a bit ago now, its got one flower on and it looks great. I haven't done a thing, just planted it in the ground with some multi -compost and its off. I feed it yesterday with a high potash feed but only cause i was feeding the delphinium next to it ( hoping for a 2nd flush). I probably feed them again throughout the year with a high potash feed to encourage flowering. They can be a bit greed dahlias, pinch the top out to make them more bushy but i just leave mine.
The tall variety usually need staking , dont forget to dead head aswell
After first frost i cut them down to about 6 inch - bring them inside turn them upside down and let them dry - then store them in sharp sand for next year.