Tangrowth's home is generally on defensive teams, where it can be used to scout Choice Band attackers by taking a blow and regenerating as it switches out to a resist, as well as wear down the other team massively with its support movepool, which features Sleep Powder, Leech Seed, and Knock Off. It can also be used effectively on balanced teams for the same purpose and to counter top physical threats, such as Breloom, who has difficulty breaking through Tangrowth even when it's asleep.
Since Amoonguss got Regenerator in BW2, Tangrowth faces more competition than ever before for a teamslot, especially since it even before was partially overshadowed by Ferrothorn. However, that is not to say that Tangrowth is entirely useless; in fact, it has several distinct advantages over its more popular contemporaries. Tangrowth has more physical bulk than Amoonguss and has access to Regenerator and Sleep Powder, unlike Ferrothorn. It can even take an offensive approach with Chlorophyll, which makes it a powerful mixed sweeper that can catch teams off-guard. Unfortunately, this is the extent of Tangrowth's usefulness. It has trouble with rain, sun, and hail teams since it doesn't have enough special bulk to stomach powerful moves such as Fire Blast, Blizzard, and even Hydro Pump. Additionally, powerful special attackers can spell an early doom for Tangrowth. Despite, its unmatched ability to take on a plethora of physical attackers allows it to thrive on certain teams.
This set takes full advantage of Tangrowth's impressive physical bulk. With Regenerator, it can safely scout powerful physical attackers, such as Terrakion, and switch out if need be, healing one-third of its health every time it does so. This gives it a great advantage over other physical walls such as Ferrothorn, as it can switch out with little to none in the way of repercussions. Sleep Powder is a great move for incapacitating a switch-in, and with BW sleep mechanics, this means that the opponent will usually remain useless for the rest of the match. Leech Seed gives Tangrowth more recovery, being especially potent against Pokemon with high HP. This also helps to heal other teammates, as Tangrowth often switches out of a seeded opponent to a better check. Knock Off is another option to make opposing Pokemon less effective by removing their item. Giga Drain is the best choice for a STAB move, as it heals Tangrowth even more and easily 2HKOes Pokemon such as Terrakion and physically defensive Hippowdon, while neither of them can break through Tangrowth. Power Whip is a more powerful option for hitting Tyranitar, specially defensive Politoed, and Jellicent, but it has lower accuracy than Giga Drain and doesn't have the added benefit of healing Tangrowth. The final move is a choice between two different Hidden Powers. Hidden Power Ice is the preferred option for hitting Dragon-types like Dragonite and Salamence, keeping them from setting up on Tangrowth while dealing with their Choice variants easily. Hidden Power Fire, on the other hand, can hit Steel-types such as Scizor, Forretress, and Ferrothorn for heavy damage, especially in the sun.Team Options & Additional Comments >>>
Although it is not the fastest Chlorophyll sweeper, Tangrowth holds the second-highest combined attacking stats of any Pokemon that gets the ability in addition to significant bulk, even without any investment. Growth is the preferred boosting move on this set, as it raises both offenses, thus allowing Tangrowth to use a strong Hidden Power. Power Whip is present as the obligatory STAB, being the best choice here due to its power and getting a hard hit on Tyranitar and Hippowdon, both of which always give sun teams issues. Earthquake provides powerful coverage on most Fire-types and Jirachi.
The last move is a choice between either a Hidden Power for more coverage or a speedy Sleep Powder. Hidden Power Ice is again the preferred Hidden Power as without it, Dragon-types will give you problems, especially Dragonite and Salamence since they 4x resist Power Whip and are immune to Earthquake. Hidden Power Fire, however, is best for hitting Scizor, Skarmory, and Ferrothorn, and gets a power boost under the sun. In addition, both Hidden Powers will deal a lot of damage to Grass-types. Sleep Powder is a final option that can be used to disable a switch-in and allow Tangrowth to get a free boost, but Grass / Ground has poor coverage and thus Tangrowth will lose to quite a few Pokemon without the help of a Hidden Power. While this set undeniably faces stiff competition from Venusaur, which is faster and more versatile, Tangrowth brings a few things to the table, such as the ability to take priority moves a lot better thanks to its great natural bulk.Team Options & Additional Comments >>>
A Choice Specs set with Leaf Storm / Focus Blast / Sleep Powder / Hidden Power Fire is also a good set, as Regenerator will allow it to play a very strong hit-and-run playstyle. Its base 50 Speed and shaky coverage holds this set back though, making it difficult for Tangrowth to beat faster teams. Synthesis can be used on the defensive sets for more recovery, but with the ever-changing weather, it is not very reliable and Tangrowth has Regenerator to heal itself anyways. Toxic is another option, as it can be used to combat Blissey, but many of the other walls that Tangrowth would like to get by, such as Heatran, Forretress, and Skarmory, are not affected by it. Rock Slide is best for hitting Volcarona and Thundurus-T, but it doesn't have good coverage on any other threats and has a low Base Power for a coverage move. Swords Dance can be used over Growth to guarantee a +2 Attack boost, but Tangrowth's relative offensive uselessness outside of sun makes it a moot point.
Checks and Counters
Tangrowth, while incredibly bulky on the physical side, can be dealt a lot of damage to by even strong neutral attacks to its frailer special side. Anything specially powerful that outspeeds and can sponge most of its attacks can comfortably switch in and threaten to KO it. However, due to Regenerator, Tangrowth can easily switch out when a counter comes in, wearing it down with entry hazards and other damage while remaining at good health itself, which often means tricky prediction is required to deal with it effectively. The threat of Sleep Powder cannot be ignored either, as losing a potential counter to sleep is never beneficial.
Latias is probably one of the best counters for the defensive set since it can set up a Substitute on Sleep Powder and then just proceed to set up free Calm Minds from there. Tangrowth cannot break Latias's Substitute with Hidden Power Ice if she is at +1, which allows Latias to either boost at her leisure or take out Tangrowth with boosted special attacks. Celebi is another excellent counter, as it doesn't have to worry about Sleep Powder because of Natural Cure and can boost, set up Stealth Rock, or simply attack while Tangrowth struggles to do anything meaningful in return. Amoonguss is also a good counter, as with its solid special bulk it takes little from Hidden Power Ice and can Spore Tangrowth or use its own Hidden Power to damage it heavily. Other Grass-types can be good counters, especially if they pack a special move. Venusaur can put Tangrowth down with a STAB Sludge Bomb, while Virizion can boost on Tangrowth and defeat it with Focus Blast or Hidden Power.
Heatran is an issue if Tangrowth doesn't run Earthquake, as it takes little from Giga Drain and Hidden Power and easily beats Tangrowth with Fire Blast or Lava Plume. Other Fire-types give Tangrowth problems because they can deal a lot of damage to it with their super effective STAB moves. Darmanitan can even push an OHKO on Tangrowth with Flare Blitz, while Victini can use Blue Flare to hit it on the special side; they both fear a possible Earthquake, however. Although Dragonite and Salamence do need to worry about Hidden Power Ice, if you have determined that it lacks it then Dragonite can easily set up on it, while Salamence can use Fire Blast or Draco Meteor to get rid of Tangrowth either way. Both of the Kyurem formes are good counters because they can either muscle through Tangrowth or use Ice Beam or Blizzard to hit it on its special side. Toxicroak is an absolute terror for Tangrowth to face in the rain, since Tangrowth cannot break Toxicroak's Substitutes, making it easy for Toxicroak to set up Bulk Ups and KO it with Drain Punch. In general, Steel-types are your best bet if Tangrowth does not run Hidden Power or Earthquake. Scizor will take a huge chunk out of it with U-turn, while Magnezone and Jirachi can set up and defeat Tangrowth with special attacks.
The Chlorophyll sweeper set is harder to counter because of its great power and coverage, but it becomes much less of a threat if it does not run a Hidden Power. Skarmory is probably the best counter overall if Tangrowth lacks Hidden Power Fire, as it can easily survive a +2 Hidden Power Ice and Whirlwind it and its boosts away. If it lacks a Hidden Power, then Skarmory is basically untouchable, boasting a 4x resistance to Power Whip and an immunity to Earthquake. Dragonite and Salamence are in a similar boat, as Dragonite can set up on Tangrowth and Salamence can beat it with Fire Blast. Venusaur can switch in on Power Whip, outspeed it in the sun, and use Sludge Bomb to wipe it out. Choice Scarf Fire-types can easily revenge kill Tangrowth because of its low Speed. Abomasnow can slow it down by changing the weather and threaten an immediate KO with Blizzard.