yes, I remember now that was part of the whole idea that came with the Hass avocados - that the grafted tree was superior to one from seed, you could guarantee a good fruit.  So what happens when you plant the seed off a grafted tree?

I'm guessing the seeds I have planted are from grafted trees.  One of them looks very different, I guess it's a sort of Siamese twin the stem is like a double stem stuck together and now there are two crowns forming.