Perennials in pots in the northern /cold states?
I live in s.e.PA. To keep these perenials(Monardas,penstemons ) in pots in our deck(which is on 2nd floor), what kind of pots(How big/wide/deep,PLastic/wood or insulated with 2 layers etc) would you recommend, so that they survive winters?
I dont wanna bring the pots in for winter, since this year I may get bigger pots(20" dia or more)
Is there anyone who has these perennials in pots in the northern states? Pls share!