This is not exactly a tutorial but more of a collection of tips and details to note when drawing vegetation. But my main advice is to avoid noise at all cost. Textures are good, but once the drawing gets too noisy everything looks weird. That's why I worry about the shape first, then about the light and only after that I worry about details.
Another useful tutorial on this topic is my pixel art fundamentals tutorial, it explains about orphan pixels and keeping a low pixel chunk count.
This tutorial was made using mostly Endesga 32 color pal!