Will favas bear in the autumn in the north if planted in summer as peas will?
Or, are they a long-day plant that won't bloom if planted this way?
I'm not a northerner but for the most part the planting times for peas and favas are the same. Here are some searches that may help:
* Broad Beans (Fava) planting date?
* (interestingly enough) The person in post #9 in the following thread recommends planting fall crops in December in Michigan: How to plant for Fall Garden?
Hope that helps!