Because they don't exist yet
There are currently only the existing 8 plants. I have Quasars unprocessed graphics for another tree and the files to do the processing. I can also probably import some public domain plants from Zoo Tycoon 2 mods (that community is gonna be a gold mine on several levels). I haven't yet because I'm hoping for Quasar to do the modular plants, in fact the latest version is a proof of concept for a low plant world.
I will probably put in some new plants to show off the potential of variety but my real goal will be when I can put them in piecemail.
Temperate shores blue? All the seas are blue, the shores are Beach, Marsh and Rocky. Marsh is the most temperate and plant filled but it's more of a green with a blue tint. Perhaps an error in shaders? I noticed my map has no shading now, though the plants still do. Not sure, must be another formating issue.