On the left hand side of the page is a link to the database. Go there and type in the name of the plant you want to add. When you find the plant in the database scroll to the bottom of the page and look for the upload photo link listed under Adding Actions.
Here is the page for Bayberry Candle.
Tall Bearded Iris (Iris 'Bayberry Candle')
To buy or trade you can post a request in the plant and seed trade forum.
