I decided to go with creating a face to face experience for my 2nd prototype. This one occurred much more naturally and I had no trouble figuring out how the learning experience would be organized.
Learners would be able to visit different stations situated throughout the garden which would have timely (monthly) topics. Each station would have expert(s) who would lead the learners through games or demonstrations of the topics. Below I brainstormed some prospective, timely, monthly topics. These demonstrations/hands on activities would take place during garden work days. Stations are mostly based around the idea engage, explore, explain, and apply. Lastly, instead of creating the app around the experience, I plan to use an existing photo based app (Instagram) to create community. If gardeners have questions or later want to share observations, they can post on Instagram with a specific tag. I think a journal/whiteboard/bulletin board or a tiny library might be good physical additions to have at the garden. Have not quite figured out what that could be yet. I still need to look up examples of participatory art. See here for zoomable photos.