You'd like to create a few different plant palette templates (Mediterranean and Asian, for instance).
To build one of your plant palette templates, open a new drawing and start a new Land F/X project.
Bring in each of the plants you want in your palette by adding them to the project. (You can also import plants from another project.)
Save the project as a Land F/X project template.
Repeat these steps for each plant palette template you want to create. Now, when you start a drawing that will use one of your palettes, start a new Land F/X project and import the plants from the appropriate template.