A plant is an object which can be bought in the store in The Sims 2. There are two different varieties, the Small Plant and Large Plant, both of which have different designs and appearances. Although the larger version can only be found when purchased in the store and placed in a room of the hotel, Small Plants can be found throughout the hotel as decorations. However, only the ones purchased and placed in rooms can be interacted with by sims, as the others aren't intended to boost your sim's sanity and are simply there for decor.
The smaller plants can be found in the Main Lobby and the Atrium along with other locations, however as you can't interact with them, there's no way to judge whether it's the same item apart from by appearance. The Large Plant can be purchased for 400 simoleons, and the small one for 300.