Plants come in two varieties. For all intents and purposes, both types of Plants are exactly the same as far as gameplay is concerned, though Plants of variety 2 (see picture) appear to be less common for some reason. Plants always have the same orientation, and are never found adjacent to a wall.
Plants may be bugged, assuming Max has at least one Bug left in his inventory. To do this, walk up to the plant and press the "F3" key. Remember that only one Bug may be installed in each room.
Note that since Plants only appear in low-importance rooms, they are not the best place to place a Bug. You will only get a +4% Surveillance Quality bonus for bugging a plant in an Office, and only +2% for bugging a plant in a Lounge.
You can hide behind a Plant when crouched, and can also jump over it if necessary.