Pokemon diamond how does budew evolve?

You must raise Budew to a high happpiness level, which can be sped up many ways:

-Get a massage from the woman at Veilstone City or The ladies in the building at the resort area.

-Use an item such as a Calicium, Protein, Iron, Carbos, Etc.

-Keep it in your party for a lllooooonnngggg time.

-Give it a soothe bell and keep it in your party for a shorter amount of time.

Giving it a berry that lowers stats.

Things that will lower it's happiness:

-Fainting.

-Bitter herbs.