Hi guys, just want to share something I found out with you all.
Normally you can only graft plants once, and has to wait for a while before the option will appear again.
Have all your cuttings ready, and then just queue all the grafting action before the first grafting is completed. And there you have it, you can graft 7 cuttings onto a plant in one go.
As another poster pointed out, you can do the same for fertilizing, which makes it faster for you to be able to evolve the plant.
The quality of the fruit produced after grafting is dependent on the quality of the plant you graft to. So you can evolve a tomato plant to Perfect, then graft all the normal, fine etc lemon, spinach, trash fruit etc cuttings onto it and voila, instant Perfect produces. Take those perfect fruits, plant them and you get a quick Perfect garden. (This section is already mentioned in Carl's guide, as the other poster pointed out, just ignore this part and look at the grafting exploit.)
Well, hope this helps!