Kobro

I'm relatively new to making mods, I've figured out the basic stuff about making blocks and items... But there's this one thing i can't seem to figure out for some reason, and there's 0 tutorials on youtube on how to do it. Foliage on blocks has me stumped, like how leaves and grass do. I've made quite a few blocks, that rotate, have different bounding boxes, collision boxes, models n stuff, but i would like a little more walk through with this to understand it more. (and maybe it'll help others understand too)