Farming & plants
Vegetables, berry trees, flowers — and the variant lottery.
Growing vegetables
Till soil with Rototiller (learned from Drilbur), plant a seed, and keep the ground hydrated — either with water beside the soil or a Sprinkler, which covers a diamond reaching 5 tiles out in each direction, up to about 60 blocks. A plant fully submerged in water will not grow, and lava nearby blocks hydration.
Plants advance one growth stage per in-game day. A Pokémon with the Grow specialty can push a plant forward one stage — or regenerate one vegetable — once per day; the plant sparkles once it has been used. Rototiller or a charged Magnet Rise can pick a plant up and move it.
Vegetables restore PP when eaten and are the ingredients for every meal, so a working farm underpins the whole move-upgrade system.
The variant lottery
Every plant and berry tree has five colour or berry variants. Each save file is given the standard one plus one random variant of each — and those are the only ones that grow natively in your game.
To collect the rest: photograph them on another player's island or a Cloud Island and 3D print them, trade with a Pokémon that happens to offer one, or watch the PC daily shop. Pokémon will also occasionally gift you variant seeds. Trees take 4 days to grow normally, flowers 1 day — or instantly with a Grow Pokémon.