I posted a question relevant to sustainability over at the gardening SE site. Is this the best way to solicit input from members of this SE?
There is indeed some overlap between Gardening SE and Sustainability SE. Your question is related to both topics and in my opinion it can be posted on either website. It's up to you on which site you think your question fits best.
One thing to keep in mind is that questions posted here that are tagged with gardening are automatically also posted in the chat of Gardening SE. Unfortunately Gardening SE does not have a 'sustainability' tag so the reverse is not possible. If you want attention from the people here I recommend posting a link to your question in our chat room.