Hi, i found this Plant Trait Database (TRY) for my university work, maybe you can have a look there. They seems to have quite some collections of traits and data.

http://www.try-db.org/TryWeb/Home.php

I do recommend TRY. You can also lookat http://traitnet.ecoinformatics.org/ (Trait-Net), http://www.leda-traitbase.org/LEDAportal/ (LEDA), 

Thank you so much

Hello. Try is a very good database but not so user friendly.

You can also try on CABI, EOL, and ISSG. There are some information on biological traits for the plants.