Here are some dynamic brushes i made. To use them, set your foreground & background colors to 2 different shades of green or brown (or whatever), set them to the size you want, & brush, or stroke a path with them. They look best if you do 2 different layers & set the top to multiply. Just play around with different blend modes & colors.
FREE for personal AND commercial use. Spread the photoshop joy around. But if you do use them, i'd appreciate it if you'd show me some love... maybe include a link so i can see what fabulous things you make with them!