I’m suspicious Turnbull giant is actually partially or completely Asian pear. I grafted it on my wild callery this spring and every graft failed due to incompatibility eventually. Had a similar experience with chojuro on parents of those rootstocks. The European pears I grafted to the trees on the second attempt all took ( some failed to late to regraft). I’ve read information on Turnbull from several different very good sources that state it’s just not that great of a pear. Korean giant though an Asian pear oddly loves the same rootstocks. The KG pears are said to easily grow to over 1 pound each. The KG are also reported to store until March since they are very hard and are yet sweet http://m.raintreenursery.com/?ref=http%3A%2F%2Fsearch.yahoo.com%2Fsearch%3Fp%3Dkorean%2Bgiant%2Bpear%26fr%3Diphone%26.tsrc%3Dapple%26pcarrier%3D%26pmcc%3D000%26pmnc%3D00&url=http%3A%2F%2Fwww.raintreenursery.com%2FKorean_Giant_Pear_OHxF97.html. Plumblee appears to be a very large pear in some situations. They say it’s very Fireblight tolerant but I had one take a strike this year on callery and was killed back to the ground. I have a few other grafts of it doing great Does anyone grow the Plumblee Pear? - #4 by Bradybb. Plumblee was a very agressive grower on my native callery which I believe led to the FB strike. The callery ofcourse recovered. This next year I’m adding plumblee to ohxf333 to slow it down some and see if that helps. I suspect it could also be partially Asian pear because it sure grows like one.