The farm shop is open from late July through to Halloween, 10-5. Naturally enough, the pumpkin patch and corn maze are fall affairs... consult their Facebook page for availability.
If you find any factual innaccuracies in this post, please email me via richard at thingstodoinportland dot org so I can fix it for everyone. Thanks in advance!
21231 Johnson Rd, West Linn, OR 97068 [Google map].