Posted: 08/10/2014 at 10:25
That depends very much on what protection you are going to use. The leaves and stems will die down entirely, leaving only the tuber in the pot, so wrapping it up at that point is fine. Please do not use bubble wrap or anything like it, it gets wet on the inside and then if it freezes will make the compost even colder - and/or damage the pot. Newspaper tied around and topped with sacking is good, or horticultural fleece if you can get some - any old curtains or cloths are fine, with the newspapers to absorb the wet. Bracken or fern leaves are excellent as packing, but not everyone has access to those. Even dry leaves tucked inside sacking or whatever will add a way of reducing moisture and keep the pot that degree or two above freezing that is all that is needed. If you can put the pot next to the house, or in a hedge (where mine go) or next to a greenhouse, or anywhere where a tiny bit of heat and protection will be offered that is even better. On the whole dahlias are pretty tough, but this is still a young one so will want a bit of help - so much depends on what kind of winter we get.