You'll have to create the ecosystem and then select the plants.  Then you'll decide the density so that your system doesn't bog down too badly.

When you're looking for plants to put in an ecosystem, look for solid growth plants.  Realm Arts, Incredibly Lush and Martin Frost, just to name a few, all do excellent work with plants that you can add to an ecosystem.

Hugz from Phoenix, USA

Victoria

Remember, sometimes the dragon wins. Correction: MOST times.