He first appears after the Pirates leave Ventureland. When met, he asks you to paint in the thinned out trees and shrubs in around Ventureland (if you put paint in the Skull Island pumps). Later, he also asks you to paint in the plants around the Bog Easy swamp.
Epic Mickey 2
In the second game, Botanist Darvin, now an unnamed Male Cow, appears at Fort Wasteland. He is first seen arguing with Ghost Ian over the Spatters in the Fort. If you remove the Spatters from the Fort using Thinner, he will remove some fake rocks covering the D.E.C entrance to the Floatyard.