This is an openly licenced icon set of commonly cultivated plants: garden vegetables, fruits, grains, and so on...
These are released under a CC0 license. They're public domain works so use them without restriction. A credit somewhere to help other people find them would be in good spirit, but is not required.
Check out the issues to see which crops need claiming and let someone know which you want to work on.
Follow the guidelines and check out some of the existing icons to maintain a consistent style with the set.
When you've got something rough, open a new issue and share your progress so the community can give feedback.
When you're done, send us a pull request with the icons in their own folder of the icons directory, each named [crop-name]-[size].svg. E.g.
/icons
/tomato
tomato-24px.svg
tomato-32px.svg
tomato-64px.svg
If you're not sure how to send a pull requst, you can always drop a zip file into an issue and someone can handle it for you