So far the edamame vine has kept growing even in below freezing temperatures. The flowers are even still blooming. Not sure how cold it will take but so far all resources suggest it doesn't grow so well in such temps. I guess we'll see how much longer it keeps growing.
Edit: I haven't fertilized them. In fact I forgot I planted them until they came up and started blooming. I had given up the pots on the side of the house since the heat over the summer killed most everything. There's also a radish or some sort of root type veggie growing in one of the pots too.