These are what I built while watching television last night. I wouldn't call them perfect representations of plantlife by any stretch of the imagination, but they are interesting to look at.
All of these are tall enough to act as cover. All of them will withstand at least two hits before being reduced to nothing. Now I really want to have a game set in some alien jungle, with all the Cover being variations on the plants in the picture above sitting on green felt. Maybe I'll actually remember to destroy cover if it's not all nice looking buildings. :-)