I’ve grafted a lot of callery through the years and not all of them are the same Wild callery pear rootstocks . It may be easy to graft them or it may be hard depending on genetics. They can be thorny or thornless which may be BET genetics Pyrus Betulifolia Asian pear rootstock crosses Favor for a friend - Top working Pears! . Callery are variable even among the pure strains Callery pear as rootstock? - #15 by clarkinks