Any Walnut Tree Experts here?

I want to ask when the best time to graft English to black root stock is. Can I do it now. There are some donor English trees not far from me with suckers the appropriate size diam. Can I root from suckers?
This is old Santa Clara County, ie Silicon Valley orchard stock that is so rare to see I'd like to start some as a restoration/saving project. This valley used to be nothing but orchards. Pear, bing cherry, walnut, apricot. I drove by the donor trees, one of the four was cut down, fruit still in their husks... Arghhhh.
Jeff back to work before it goes to India.

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