SOME NOTES ON THE JAPANESE WALNUT IN NORTH AMERICA
Dr. J. A. Neilson, Michigan
The Japanese walnut, Juglans sieboldiana, and its varietal form cordiformis, were said to have been introduced into America from Japan about 1870 by a nurseryman at San Jose, California. From this and other subsequent introductions a considerable number have been grown and distributed in the United States and Canada.
A recent inquiry by the writer brought forth some interesting data relative to the occurrence and distribution of this species in North America. This inquiry shows that it has been widely distributed and is reported in the following states: Arkansas, Arizona, Alabama, Connecticut, California, Delaware, Illinois, Iowa, Indiana, Kentucky, Massachusetts, Missouri, Minnesota, Maryland, Maine, Mississippi, Michigan, New Jersey, New York, New Hampshire, Ohio, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, West Virginia, Washington, and Wisconsin. No reports were received from South Carolina, Louisiana, Montana, North Carolina, North and South Dakota, Idaho, Georgia, Colorado, Kansas, Texas, and Wyoming, and negative reports were received from Florida, New Mexico, Nevada, Oklahoma, and Tennessee.
In none of these states is the Japanese walnut abundant in the same degree as other kinds of nut trees, but in some states it was reported more frequently than in others. It occurs more abundantly in Pennsylvania, New York, Connecticut, New Jersey and Delaware than in other states.
In Canada it has been reported from Prince Edward Island, Nova Scotia, New Brunswick, Quebec, Ontario, Manitoba, Alberta and British Columbia. In Ontario it is found occasionally from Windsor to the Quebec boundary and from Lake Erie to North Bay. There are several fine large trees in southern Ontario, some of which are worthy of propagation. Many of the trees in Ontario and other eastern provinces grew from nuts distributed by the writer several years ago. For five years in succession the writer bought the crop from a large heartnut tree near Jordan Station, Ontario, and distributed the nuts all over Canada to those who were interested. More than twelve thousand nuts were thus distributed and I know from observation and reports that seedling trees are now growing from the Atlantic to the Pacific. I am going to tax your credulity to the utmost and tell you that one of my correspondents reports heartnut trees growing in the Peace River area of northern Alberta. I have no recent report from my friend but I know that the trees came through two winters in that far northland.
Possibly in the days to come a superior seedling or a hybrid may be found in these numerous seedlings which will be worth propagating. Some of these trees have already borne nuts and many have made very good growth.
The Japanese walnut has also been reported from New Zealand and several states in Australia, England, France, Germany and other European countries.
Climatic Adaptation
From the foregoing it can be seen that this species of walnut has been widely distributed and is now growing in countries with a wide temperature range. Reports are on hand which show that the trees have endured temperatures of 40 below zero F. to 110° above zero. From this it need not be assumed that all Japanese walnut trees will stand great extremes of heat and cold, for experience shows that they will not. It does show, however, that some individuals at least have marked hardiness to cold and heat and have endured temperatures much greater than the English walnut. The best results in growth and fruitfulness have been obtained in those regions of moderate rainfall where the apple and sweet cherry grow successfully.