black sapote

vin starts with ...
have black sapote tree in my yard, produced lovely fruit, finished picking mid september. have germinated some seeds and now standing above ground with seed pods still ontop. do i need to graft the trees to produce and if so when. if i decide to keep some in large pots do i still need to graft and what potting mix should i use. or could i make my own as i did with the seedling mix. did not include pic as i have no plant problem at this stage. thank you, vince