hey jim .. welcome ...

do you literally mean grafting on what comes up in a few months???

most tree grafting.. involves an understock that is at least pencil thick ... which is about 2 to 4 years old ....

i would suggest you get some cactus mix.. and some one gallon pots .. and try potting up your seedlings.. and learning how to grow trees in pots.. for a year or two.. to grow them to size.. so as to graft them ... in the future ...

otherwise.. generally.. trees are grafted in winter .... and i bet you missed your window of opportunity.. but i dont know for sure... but fruit peeps do things much differently than tree peeps.. so who knows ....

there is a fruit forum .... and some of those peeps do 'nuts' .... and i have never seen most of them here.. so you might want to try the same question there ... if you dont get an answer here ..

good luck

ken

I have 3 black walnut seedlings that are 2 years old, that I transplanted last year into where I wanted them to grow.

I was under the impression that grafting can be done in early Spring while the plants are still dormant. I was going to graft some branches of the top onto the suckers, coming up from the root.
The roots are of a stock used for dwarfing. :)