Bellsprout has a 25% chance of being found on Routes 5, 6, 24 and 25. It has a 20% chance of being found on route 7 and Bond Bridge, a 30% chance of being found on Route 12 and Cape Brink and a 35% chance of being found on Routes 13, 14, and 15. It also has a 5% chance of being encountered in Berry Forest. Weepinbell has a 5% chance of being found on Routes 12, 13, 14, and 15. It has a 10% chance of being found on Bond Bridge, a 15% chance of being found at Cape Brink, and a 20% chance of being found in Berry Forest. The line is a Leaf Green exclusive and cannot be found in Fire Red.
Congratulations, Leaf Green Nuzlocker! Whether it was your intention or not out of the two choices for ubiquitous Grass types you got the much better deal. Compared to Oddish, the Bellsprout line sports better a better movepool along with better Offensive stats at the cost of less bulk. Even outside the comparison to other game's grass types Bellsprout holds its own as a decent choice in a Nuzlocke. Weepinbell and Victreebel have great offensive power in both categories and can take advantage of both their STABs, a rare sight before the Physical/Special split. Unfortunately its movepool only looks good when compared to a Pokemon with a set as bleak as Oddish. Without TM support your only means of offense until level 42 will be Acid, Wrap and Vine Whip, and its mediocre speed doesn't go well with mediocre defenses. Still, with the right TM support and perhaps a bit of sun to brighten its day, this pitcher plant can go straight to the top.
Gym #2 - Misty (Cerulean City, Water-type): This is Bellsprout's jam. If it's a Weepinbell now or even just leveled up to around 20 or so, Vine Whip wrecks the Gym. Don't worry about the Star's part Psychic typing, they know no Psychic moves.
Rival (S.S. Anne): You should have a Weepinbell at this point, and depending on what starter you chose it'll be useful for about half the Battle, or none of it. Kadabra should be avoided like the plague, as should Pidgeotto. Even if you have Acid neither are worth fighting. Raticate can be beaten pretty easily, just watch out for Hyper Fang as usual. Finally his starter choice really makes or breaks this battle for Weepinbell. If its Wartortle obviously the pitcher plant makes a good match, if it's Charmeleon then stay far away. Weepinbell actually makes a good matchup against Ivysaur as Leech Seed does nothing to it, and it resists Vine Whip, just make sure you have Acid if you want to deal damage.
Gym #3 - Lt. Surge (Vermilion City, Electric-type): There are better options, like a Diglett. However if you don't have any ground types due to some unfortunate reason, Weepinbell is a decent choice. Just know Thunder Wave will get really old, really fast, and Voltorb's Sonicboom can hurt. Put Raichu to sleep as soon as possible because Double Team will make you hate life. Other than that, Vine Whip/Acid away and have fun!
Rival (Pokémon Tower): Pretty much the same deal as before, only now Ivysaur is even easier to fight as Tackle has been replaced with Poisonpowder. Kadabra is underleveled and can actually be challenged if you think you can outspeed it and you have a strong enough physical attack, but that's not something I'd recommend. Gyarados is a pain in the ass, and Thrash can cause problems, but if you're stronger than it Weepinbell can probably take it on, preferably with Vine Whip due to Intimidate. Exeggcute gets melted away with Acid easy. Growlithe should obviously be avoided.
Giovanni (Rocket Hideout, Ground-type): The ease of this depends on if you have a shiny new evolution to work with or not. Obviously Onix and Rhyhorn go down quickly, but Kangaskhan poses problems and might be too much for Weepinbell if it's not overleveled. If you can't put it to sleep, Victreebel can tank it, and Weepinbell probably will just be hurting, but keep an eye on it.
Gym #4 - Erika (Celadon City, Grass-type): The good news: you resist everything she throws at you. The bad news: she resists everything you throw at her. Except for Tangela, that gets hurt pretty bad by Acid. If Victreebel knows a normal type move it can speed things up here a lot, otherwise this is going to be a stallfest.
Gym #5 - Koga (Fuchsia City, Poison-type): This is an interesting one. Like with many battles this late in the game, there are always better options. In this case you should probably take them. Victreebel resists Toxic and Sludge, meaning Koga can only do two things Evasion/Accuracy hax, and Explode. Selfdestruct will kill, no question. Which means you're playing with fire if you can't OHKO the Koffings. Provided you can do that, Muk and Weezing are certainly doable, but be prepared for a lot of anger from Minimize and Smokescreen.
Fighting Dojo (Saffron City, Fighting-type): Most of these guys can't do jack to Victreebel thanks to it resisting Fighting type moves. Even against Koichi, Hitmonlee isn't any problem, it's Hitmonchan you need to watch out for, Fire Punch or Ice Punch hurts. Either switch to something better suited for the job when he shows up, or be sure you can OHKO/tank those hits.
Rival (Silph Co.): Finally you get to fight your rival with Victreebel, and unfortunately his Pokemon have evolved too. Pidgeot is even more dangerous than it was before, avoid at all costs. Alakazam looks tougher than it is, only knowing Future Sight as an attack. Victreebel can fight it if you want, especially if you're packing Return, but keep an eye on the turns as it'll definitely hurt once it fires one off. Exeggcute is still easy if you still have Acid, though the Level 38 one that shows up if you picked Bulbasaur knows Confusion, so pay attention to that. Growlithe is still a problem, but Acid or Return hurts it, and if you're overleveled Ember isn't as threatening as it used to be. Probably should be avoided. Gyarados is tougher, but so is your Pokemon, again it'll probably be a lot more brutal than you'd like but definitely doable.There are probably better options. As far as his starter goes, Blastoise and Venusaur are still good matchups, but Venusaur will probably take longer to kill due to bulkiness. If you ever thought Victreebel could take on Charmeleon, those days are over as Charizard will burn it to a crisp.
Giovanni (Silph Co., Ground-type): Does your Victreebel know return? If so this is going to be a lot easier than it would be otherwise. Honestly don't bother if it doesn't, Nidoqueen is bulky enough to make Razor Leaf/Giga Drain slow going in terms of the kill. Kangaskhan isn't as bad as it was in the first battle, but still a tough opponent. Rhyhorn is a joke. Honestly a Water type does this job a lot better.
Gym #6 - Sabrina (Saffron City, Psychic-type): You. Will. Die. Sooner or later one of those Pokemon will fire off a Psybeam or Psychic and take you down. Just don't do it.
Gym #7 - Blaine (Cinnabar Island, Fire-type): See above, only it'll happen a lot faster.
Gym #8 - Giovanni (Viridian City, Ground-type): Finally somewhere Victreebel has some use! So your only problems here will be the Nidos, as everything else goes down pretty quickly. Still, Grass type moves hit for neutral damage on them, so Giga Drain isn't exactly a terrible option here. Return is a lot better though, and your pitcher plant should love you for taking it this far.
Rival (Route 22, pre-Elite Four): Much of the same as its always been. Pidgeot and Alakazam are now way too tough to mess with. Blastoise, Rhyhorn and Exeggcute are easy to take down. Gyarados is a lot easier than it looks at this point. Growlithe is probably best avoided as Flame Wheel is much stronger than Ember was, as is Charizard obviously. Venusaur is going to be a drawn out affair without status support, as Synthesis can be annoying if your strongest neutral move is still acid, still doable though.
Elite Four Lorelei (Indigo Plateau, Ice-type): You don't know how badly I want Victreebel to be good here, but unless you're super confident in its ability to outspeed and take at least one Ice Beam it'll probably be useless. Sunny Day helps here, as that gives both speed and access to Solarbeam, which has a good chance to OHKO if you're overleveled. Regardless of what you decided to do, just get the hell out of there when Jynx shows up.
Elite Four Bruno (Indigo Plateau, Fighting-type): Victreebel is actually good here! It resists Fighting type attacks, and while it can't hit anything but the two Onixes really hard, but still can hold its ground. If you went the stall route and taught it Toxic, it'll be handy here. Just remember Machamp has Guts, and is probably best dealt with by something with Psychic.
Elite Four Agatha (Indigo Plateau, Poison-type): It's not that Victreebel is the WORST Pokemon to use here, but it's pretty bad. Acid and Grass moves are resisted by all parties here, and Double Edge/Return won't hit the ghosts. Don't try it.
Elite Four Lance (Indigo Plateau, Dragon-type): Not a good bet unless you like risk, Hyper Beam from any of his Pokemon won't be fun. Even then, Dragonite and Aerodactyl will be packing Wing Attack and will likely kill. Really all Victreebel can fight here are the Dragonairs, and that's only if it has Double Edge or Return, preferably the latter as the recoil could mean death if it has to take a Hyper Beam. Just use an Ice Type and save yourself some pain.
Champion Rival (Indigo Plateau): Pretty much the ultimate culmination of all issues with your rival battles in the past. Pidgeot, Alakazam, and Arcanine are truly dangerous with their strong moves and resistances. Rhydon and Exeggutor are pretty easy, though if your strongest move on Exeggutor is still Acid this probably means it'll be a slow affair. Rhydon goes down pretty handily with Giga Drain or anything stronger. Gyarados is going to be tougher as it suddenly has Thrash again, the choice of fighting it is up to you, I didn't take the chance. Charizard is bad, I don't need to say it again. Blastoise will be slow going if you still have a weak grass type move, but you should at least be packing Razor Leaf, so it shouldn't be too awful. If you taught Victreebel Return or Double Edge, its moment to shine will be against Venusaur. Once it pulls out Sunny Day, you outspeed it and resist its only attacking move. Return is a lot better than Double Edge as Venusaur knows Synthesis and could still stall you out with the recoil. Nonetheless nothing is more satisfying than turning Blue/Gary/DICKS own moves against him.
Assuming you catch one on Route 24 or 25, Bellsprout will start out knowing Vine Whip, Growth, and Wrap. It will also learn Sleep Powder very quickly at level 15. This all in all makes for a very good moveset this early in the game, and won't need too many changes to carry you through the next few challenges. Poison Powder comes in at level 17 and Stun Spore at 19, all three status powders are good moves in their own right for teams that like messing with their opponents, but all three are not needed on one moveset usually. Feel free to replace Growth with one of them though, you can also replace Wrap if you like the stat boost, but be wary as this leaves Bellsprout with only the 10 PP Vine Whip as an attacking option. After evolving at Level 21, Weepinbell gets Acid at level 24 which is a welcome secondary attacking option that isn't Wrap, it's a must have. At this point you really should make a choice as to whether you're going to teach your future Victreebel a Grass Type TM. If not, you'll have to keep it as a Weepinbell until level 42, when it learns Razor Leaf, I really don't recommend this at all. Otherwise, evolve it now. The only other moves it gets via level up are Sweet Scent at level 33, which is garbage, and Slam at level 54, which is inaccurate and not worth the wait.
Bellsprout gets great options via TMs but not much versatility. Bullet Seed is a great early game alternative to Vine Whip, but loses a lot of luster early on, and sometimes is unreliable. Giga Drain is an incredibly good option for Victreebel as it circumvents waiting for Razor Leaf and is a stronger move anyway, highly recommended. Return is a highly useful option for taking advantage of Victreebel's great Attack stat in ways Acid doesn't, but if there are others who want this TM more, Double Edge makes a great alternative. Victreebel wishes Sludge Bomb was available before the post game, badly, but sadly you'll have to make due without. Like many Kanto Grass Types, Victreebel makes for a stunning Sunny Day user, Solarbeam provides massive damage and Chlorophyll makes Victreebel's speed a non issue, allowing it to ravage most enemy teams. However, this requires investment and usually other teammates who benefit from the sun to be worth it. If you want to stall, which Victreebel can do semi-effectively Toxic is a must as usual. Victreebel also learns Cut and Flash, but really, just get an HM slave for these moves, you'll be happier for it.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Bellsprout Line Ratings
What Nature do I want? Mild or Lonely are probably your best bets overall depending on which attack stat you want to focus on. Avoid natures that lower either of the Attacking stats, most Victreebel sets are going to have to be mixed attackers, so ironically Adamant and Modest aren't the best options here. Lowering Speed isn't preferable either, especially if you're not going to have any sun support.
At what point in the game should I be evolved? Depends on if you're going to use Giga Drain or Solarbeam, which I can't recommend enough. This lets you evolve right away if you don't care about getting Acid, or at level 24 if you do. Either way having Victreebel early on makes for a terrifying prospect against most foes. If you're going to wait for Razor Leaf, then you're going to be in it for the long haul, as the move comes at a late level 42.
How good is the Bellsprout line in a Nuzlocke? Bellsprout is a fantastic Grass type Pokemon, notice the caveat there. It runs circles around most other available Grass types, as only the Bulbasaur line and Exeggutor are really better than it. In fact, it makes an excellent Venusaur stand in/replacement in case that's what your team needs. However that being said, its movepool is very limited and it leans on TM and Move Tutor support. Even though its stats are decent as well, other Pokemon in the game generally have better distributions and run circles around it in terms of versatility. Nonetheless Victreebel can definitely surprise you if you know what you're doing and give it the proper moves. Overall a very decent Pokémon.
Weaknesses: Flying, Fire, Psychic, Ice
Resistances: Fighting, Water, Grass, Electric
Neutralities: Normal, Poison, Ground, Rock, Bug, Ghost, Steel, Dragon, Dark