Greeks: Theophrastus mentions hazel nuts but nothing about walnuts.
Romans: Pliny, Cato, etc. have little to say about walnuts. Pliny refers
to planting seeds of walnuts but no other method of propagation.
However, he states oaks and walnuts are poisonous to soil, and walnuts
are only used in a few cases for human remedies.
English: Loudon, Evelyn, Knight, etc. Loudon sticks to propagation of
walnuts by seed. Knight[8] followed the French practice of grafting
walnuts by approach up to the time of his discoveries in 1832, which
were similar to Dr. Morris's "immediate" grafting.
French: The French used grafting by approach (inarching) early in the
19th century. Mortillet[11], 1863, states only one-third to one-half of
walnut grafts are successful. These were probably Persian walnuts. We
are not sure what other methods the French used. Mr. C. E. Parsons of
the Felix Gillet Co. in 1940, sent us a picture showing Felix Gillet in
his greenhouse at Barren Hill Nursery, Nevada City, California. This
picture he states was taken in 1900-1902. It shows one year grafted
walnut trees, and bench grafted walnut trees covered by tumblers six
inches high, grafted by the "Treyve" process.