Join Date: Feb 2016
Location: Central California
Most Ludwigia species grow pretty fast and creep around. I have Ludwigia repens 'Red' and Ludwigia arcuata growing emersed right now. In high humidity, the L. repens will stay very red.
If you want just one single plant to grow like crazy, I recommend Hydrocotyle tripartita (aka Hydrocotyle 'Japan'). It grows SUPER fast emersed, to the point where it's kind of become a nuisance in my setup.