Preface: This idea came to me while thinking about how to better give planets a sense of distinctiveness, while at the same time reducing workload.

Basically, the idea would be to procedurally generate up to four distinct plant species per planet by mixing and matching attributes found in plants on Earth. These species could then be saved with a minimum of overhead and rendered on any map taking place on that planet. That would give each planet a unique ecology without the need to tie up an art team for five years thinking up alien grasses.

So, each plant species would have several attributes:

1. Size 1-4 (Ground Cover, Bush, Small Tree, large Tree)
2. Branching model (use existing earth plants as models:Grass, Bamboo, Pine, Oak, Cactus, Rose, etc) this determines the basic structure of the plant
3. Trunk Texture (Barbed-Rose, Bark-tree, Scale-palm tree, Bamboo, etc)
4. Trunk Color
5. Leaf Model (Palm frond, oak leaf, lilly pad, pine needle, fern frond, etc)
6. Leaf Size
7 Leaf Color

Each planet could randomly generate one plant species of each size and store the attributes. So for example, you could have a tree sized cactus-like plant with a palm-tree-like skin in pale yellow covered with tiny purple fern-type leaves.

Then when the planet is rendered for a battle, the unique species of that planet are rendered and slotted into the maps. This could be further modified by biome (desert maps would maybe only render bush sized planets, or grasslands just large trees and ground cover, for example), lattitude, or whatever.

Basically, this system could produce a uniqueness to each planet that would be easily recognizable without a lot of overhead in the art department.