Finding the best Grass-Type Pokémon in Pokémon GO will allow you to win certain matchups.
Best Grass Type Pokémon GO 2020: Top 5 Grass Types in Pokémon GO
Among all of the dual Grass and Poison types, Venusaur is the best. The final evolution of Bulbasaur, it learns strong Grass and Poison-type moves. It's not as hard-hitting as other Grass types, but the increased bulk Venusaur has lets it stay in the game and dish out attacks longer.
Breloom gets to use its unusual type combination to make a name for itself in Pokémon GO. Since it can learn Fighting moves, it lets it cover a variety of threats. It can even cover for its Ice weakness. Just watch out for Flying moves, as Breloom is weak to them.
The Dark and Grass Shiftry also takes advantage of a unique typing. Grass Pokémon are good against Water/Ground Pokémon like Swampert that dominate the Ultra League, but Shiftry's Dark attacks let it deal with equally as common Psychic and Ghost types.
Roserade doesn't sport the same bulk as Venusaur, but can still fill a similar role. It's overall not as powerful as Venusaur but can put up a good fight. If you can't get a Venusaur with Frenzy Plant, Roserade is your next best choice.
Sceptile is a silver bullet against Water/Ground types. It's quick and hits hard, letting it take down bulky Water, Ground and Rock types before they can charge up and become a threat.