Budew is a Grass and Poison-type Pokémon that is fairly easy to obtain after a couple of hours playing Pokémon Legends: Arceus and can be evolved into Roselia and then Roserade.
In order to evolve Budew into Roselia, you’ll want to unlock the Friendship Checker, which is an NPC that stands near the pastures who will tell you what the friendship level is of the Pokémon you choose to show him. This will be helpful, because Budew must have a maxed-out friendship level in order to evolve it.
To get Budew to evolve, its friendship level must be maxed out during the day. There are multiple ways to increase friendship with your Pokémon, including giving it berries, keeping it healthy, and not allowing it to faint in battle. Gathering resources out in the wild with your Pokémon will also help with friendship level.
During the day, when your Budew has a max friendship level, the Pokéball next to its picture in the party screen will blink and it can be evolved into a Roselia.
Budew is pretty easy to find once you’ve entered into the Crimson Mirelands. It will be at the Golden Lowlands and the Gapejaw Bog. It can also be found in the Coronet Highlands in the Fabled Spring.