At what time of year do you pick young walnuts to make pickled walnuts?

Answer 1

Sept. And October. Check them while on the tree though. They should be well formed but still soft. You can start picking them as soon as they have reached a decent size and keep picking until the shells start to get hard.

Answer 2

You have a couple more months to go:

http://www.ipm.iastate.edu/ipm/hortnews/1994/9-16-1994/bnut.html