If you have a little patch of dandy lions, you can cover them with leaves or a box or some little insulation and they can be harvested any time... They need some light now and then,,.. so you might give them some light now and then by lifting the box or raking the leaves back on a sunny day.. I have harvested dandy in the middle of winter by just raking some leaves, there is always some dandy lion sitting there waiting to be ate.
I would imagine that the root could be dug in the late fall and the root could be brought inside a shed or basement, and kept in sawdust or sand or dirt/sand or vermiculite mix and given a little light now and then and some moisture...
IT is one of the hardiest plants around.
Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.
We have considered dehydrating the leaves and root for later use. The leaves for soups and salads, the roots for coffee substitute and seasoning. Peppermint is in the dehydrator now, I will try a batch after that and let you know what it looks like.