Hmmm... We know three possible environments:
Strong Sunlight Boosting Plant Growth
Tundra that has Pokemon adapt to it's low temperature
Theory Volcanic that has Pokemon adapt to it's harsh heat
So with the Exeggutor's massive growth I would theorize that Pokemon that evolve from the Leaf Stone and possibly the Sun Stone will have an alternate massive form from the sunlight. So I think that these Pokemon start as their normal sized selves and if you would cause their evolution in the proper environment they will evolve naturally without the stone instead taking their Alola form instead.
I expect Vileplume will become a Grass/ Fairy type with a more pleasant scent. Oddish has the ability to learn Moonblast naturally so I expect the Fairy type change for it's Poison type.
Victreebel being a predator will most likely become even more direct tactics dropping it's Poison type in favor of Fire. Fire typing allows it to not only hunt Bug Types better but even other Grass Types.
Wonder if Sunflora will finally show it's true power? Perhaps it will become a Grass Fire Type as well?
Strong Sunlight Boosting Plant Growth
Tundra that has Pokemon adapt to it's low temperature
Theory Volcanic that has Pokemon adapt to it's harsh heat
So with the Exeggutor's massive growth I would theorize that Pokemon that evolve from the Leaf Stone and possibly the Sun Stone will have an alternate massive form from the sunlight. So I think that these Pokemon start as their normal sized selves and if you would cause their evolution in the proper environment they will evolve naturally without the stone instead taking their Alola form instead.
I expect Vileplume will become a Grass/ Fairy type with a more pleasant scent. Oddish has the ability to learn Moonblast naturally so I expect the Fairy type change for it's Poison type.
Victreebel being a predator will most likely become even more direct tactics dropping it's Poison type in favor of Fire. Fire typing allows it to not only hunt Bug Types better but even other Grass Types.
Wonder if Sunflora will finally show it's true power? Perhaps it will become a Grass Fire Type as well?