Have a look at the Nov issue of scales and tails, there is an idea of some plants that do ok in reptile enclosures if maintained properly. I find most small species of tropical house plant with the light lighting and water will grow quite well, I don't know exactly what the substrate composition is and its mineral levels but mixing it with washed river sand and orchid bark may help. Just be careful not to put the health of the plants first. If you give me an idea of the enclosure type and reptile species i may be able to help out more.
Mike