It would be excellent to find a mapping tool that allows online collaborative editing and plotting of plant species (including individual trees), designation of usage zones, and the like.

OpenStreetMap seems interesting but I am not sure if that sort of thing can be used for local (non-publicly-noteworthy) information.
QGIS seems alright but not the best in terms of usability.

It's probably essential to have a mobile app for logging data, including photos of weeds/natives with their geolocation.