Why didn't Ash's Torkoal ever evolve in the Pokémon anime?

Mega Evolution: Torkoal by AnaMorte on DeviantArt From com Type: FireRock Ability: Magma Armour As requested by a few, Torkoal has had

Torkoal; Spinda; Cacnea; Cacturne; Zangoose; Seviper; Lunatone evolutions to work in Gyms Pokémon that have fainted can be used as

torkoal evolution In-Progress Pokemon Evolutions What if Pokemon grew into their stages instead of evolving instantaneously? In-Progress Pokemon explores how

torkoal evolutions It didn't evolve because it physically cannot Torkoal does not evolve into, or from, another Pokémon It is the only one in its evolution line