The interesting thing about villainous plant creatures is how amorphous they are, and how they usually influence the vegetation around them. The interesting thing about trees is how they manage to wreak terror and destruction while being, for the most part, stuck in one place. You might think that there is a limited amount of havoc such a being would be able to cause, but just take a look at this list and prepare to eat those thoughts.
10) Baobabs, The Little Prince
Baobabs are real trees with thick trunks and potentially nutritious fruit. Some of the larger specimens have had their trunks hollowed out to create buildings, and one such structure served as Rafiki's house in The Lion King. They don't seem to have any particular sentience, and therefore no real potential for malice, right? Well, tell that to Le Petit Prince. In case you don't remember French 301, the Little Prince lives on a tiny planet and spends his time protecting one measly rose from these pesky things (there are also volcanoes, but somehow the trees are more menacing). In the story, the Baobabs are simply a nuisance, but in the cringe-worthy opera adaptation (2:40-4:53 above) they take it up a notch by wiggling around and threatening to "stick their roots right in you". Dear lord.
9) Dark Forest Trees, Legends of the Hidden Temple
These trees may not have been alive per se (sometimes they were possessed by evil spirits, sometimes there were just temple guards hiding in the trees) but they still count as they scared the bejesus out of me, and (I hope) other pre-pubescent Nickelodeon viewers. The "Shrine of the Silver Monkey" may be the most fondly remembered single temple chamber, but far more suspenseful was the Dark Forest (about two minutes into the above clip), in which contestants had to stick their hands into random tree trunks in search of the right key. All of the trees in this room were creepy, but only one was inhabited by a temple guard. Pick the wrong tree and it would snap up its stiff arms around you in a flash: a beautiful combination of Dagobah, child abduction and Russian roulette. Instant classic.
8) Evil Tree, The Mighty Boosh
Based on that name alone, it'd be hard to make a list of evil trees without this guy. Brought to life by the evil green Hitcher and his ludicrous Cockney bellowing, Evil Tree's sole purpose is to keep the Boosh team from reaching the fountain of youth (he was also a late addition to the script. Shocking, isn't it?). Tip: when facing evil wood creatures, it's always handy to have a man made of sandpaper on your side, even if he is a seven-foot-tall wanker with wire eyebrows.
7) Groot, Marvel Universe
6) Whispy Woods, Kirby Series
I know it's not a particularly hard boss or anything, and there's nothing overtly menacing about it, but look deeper. Something about that vacant stare, that innocent expression, that simple face, masks a deep anger. This is a tree that only knows life through confrontation, that wishes complete misery on you, both as a player and a human being. Whether it's the classic one-side-of the screen battle, the double onslaught from Kirby Superstar or the bizarrely impressionistic one from Dreamland 3 (you know, the one where it GETS UP AND STARTS CHASING AFTER YOU), this tree ain't right. I don't trust it, and I have no sympathy for it, even if it does shed a sad single tear on defeat.