Is it possible to assign a custom block to one of the plant species representation types?

Yes it is.
  1. Create the geometry to use as one of the representation types for the plant species.
  2. Save it as a new file in your PC. (Make sure this geometry has its bottom center point located on the document origin coordinates). You can use the “File > Export with Origin..” option to save the model as a new file and set its base point.
  3. Select the plant species to edit, from the Selection list, in the top left side of the Lands Edit Panel. (Make sure no object is selected to display the list of plant species inserted in the model).
  4. In the Properties area of the Lands Edit Panel, under the Species tab, select the Change button of any representation type to open the block explorer and look for the file you have created before.
In Lands Design a Rhino model of a plant is being assigned as the plant species representation.

Note

This custom block can’t be assigned to the realistic representation of species, that is used by an “nxt plant” file. If you want to show the other species in realistic mode at the same time as your custom block, assign it to the Detailed representation, and uncheck the “nxt Plant” representation:

The Lands Design panel with the several models for the plant representations and the field