The most type-weaknesses in the game (5) — but unmatched utility.
Grass has five weaknesses — Fire, Ice, Poison, Flying and Bug — which is the most of any single type in the game. That sounds crippling, and defensively it often is, but Grass compensates with the deepest utility toolkit: Leech Seed, Spore, Sleep Powder, Giga Drain self-healing, Rage Powder for doubles redirection and Grassy Terrain for team-wide recovery.
Grass is a stall and support type at heart with occasional offensive stars. Ferrothorn and Amoonguss are the poster children — walls that spread status, soak up physical attackers and win by attrition. Sun-based Grass teams use Chlorophyll abusers (Venusaur, Lilligant) for double-speed sweeping.
Giga Drain (75 BP + 50% HP recovery) is the go-to special Grass move for survival. Leaf Blade crits 50% more often. Wood Hammer is the 120 BP nuke with recoil. Grass Knot scales with target weight — hits heavy mons for 120 BP.
Bulbasaur is the only starter whose number is #001 in the National Pokédex, and its name is a portmanteau of 'bulb' and 'dinosaur' — not a direct Japanese loanword like most starters.