Depending on the animal, the most realistic option is 'no plants'. While this is difficult to do if you want the habitat to look especially beautiful, some animals in real life are very destructive towards plant-life and so many zoos opt to keep heavy planting on the habitat perimeter out of reach of the animals, or they don't use any plants at all (besides perhaps a ground cover of grass). Elephants, for example, typically are not exhibit with a lot of living plants, and neither are many primate species (which is why zoos often use artificial climbing frames as an alternative and a lot of rockwork, or fake trees - it might look 'low budget' but it is common practice).
Though I imagine this isn't the answer you're looking for and obviously isn't the case for all (or even most) species.
As Dinocanid says, specifically listing the plants is difficult, but it's more or less broken down into "trees" and "shrubs". So the tree fern takes up space, but the lobster claw plant doesn't. The river bushwillow takes up space, but the arrowood bush doesn't. AFAIK the only 'shrub' that can't be clipped through is the elephant grass (perhaps the reeds as well?).