Walnuts are considered to be the oldest tree known to man and have the botanical name of Juglans which is said to stem from the Roman appellation Jovis glans meaning Jupiter’s nut or, more loosly, nut of the gods.
The English word Walnut is considered to be either a linguistic creation of the word Gaulnut or derived from the Anglo-Saxon word wealh meaning foriegn. The term English Walnut is derived not from its origin, but probably from its widespread transport in English merchant ships.
The origin of walnut trees found today is a matter of long standing dispute. However, the current view is that walnut trees originated in Persia over 7000 years ago and were transported from Iran and Turkey to the mediterranean region by Greek traders. Roman traders then further extended walnuts into North Africa, Western Europe, and as far north as England where they assumed the name of “English Walnuts”. Walnuts also appear to have been traded along the Silk Road route between Asia and the Middle East.
Although early efforts at walnut grafting were probably undertaken in many countries, horticulturalists in France were the first to successfully graft walnuts on a routine basis which laid the foundations for modern walnuts.
Todays successful walnut varieties owe their success to a combination of natural factors, careful variety selection and the introduction of separate rootstocks to provide more vigorous growth. However, most modern varieties are descendants of the Payne variety which appeared naturally on the walnut orchard of G.C Payne, in California in 1898. Prior to the arrival of the Payne variety all walnut trees were considered terminal bearing; meaning that walnuts only grew on the furthermost tips of each branch. However, on the Payne variety walnuts grew along both the branches and at the tips thus resulting in improved variety of walnuts commonly referred to as lateral bearing walnuts.
In addition to natural factors an extensive breeding program has also been carried out at the University of California (Davis) since 1948 whereby different varieties have been cross polinated by hand and the resulting trees analysed for both yield and quality. The long term nature of this breeding program can be illustrated by pedigree charts which clearly trace the development of the two most recent varieties (Chandler and Howard) back to the original Payne. These pedigree charts are almost identical to the pedigree charts used for horse racing except that they are for walnuts.