The lone tree, which produced three bushels in 1949, was of interest. Investigation revealed that the nearest Persian walnut tree was at least a city block distant. Was this lone tree self pollinating or receiving pollen from a tree this far away? We still are not sure of the answer.
Jacob Houser, of Lampeter, was selling Pomeroy seedling nuts and nuts from three Rush Persian walnuts grafted on black walnut stock. They were growing close enough for cross-pollination.
Driving through the counties of southeastern Pennsylvania, we found many thousand seedling Persian walnut trees as shade trees about the farm homes. Investigations revealed that most of these trees never produced any nuts. Repeatedly we are told that, "my tree never has any nuts, but a certain tree on an adjoining farm always produces," or "I have two trees, one of which bears quite regularly but the other never has borne." They are the same age and both seem to be growing equally well. Some produce only a few handfulls of nuts when they should be producing five to ten bushels, judging by their size.
You as nut growers know the answer, but the general public does not. Even some of you have made the mistake of planting one tree by itself and expecting it to produce. This seldom happens. Mixed plantings of several varieties or several seedlings planted close together is the safe rule to plant by.
I know of one planting of ten grafted trees of one variety of Persian walnuts, now twenty years old, that has never produced any nuts even though they are planted so that cross-pollination would be expected. In 1950 only a few catkins developed. These produced pollen early and were on the ground before the pistilate bloom opened and was receptive. I never saw a nicer pistillate bloom on any Persian walnuts than these trees had, yet not a single nut set. They are in the center of a fifty-five acre black walnut orchard, and when the pistillate bloom was at its peak, the black walnuts surrounding were shedding pollen. Do not try to tell me that native black walnuts will satisfactorily pollinate the Persian walnut. After this demonstration, I know different. Were all the Persian walnut trees of Pennsylvania properly pollinated, the crop of nuts, in my estimation, would be increased a hundredfold over what it is normally. Lack of pollination is probably the greatest factor causing non-production in our Persian walnuts. It is far more important that the fertility factor which is so important in production of the common black walnut. (2)
Fayette Etter and Milo Paden both feel that the Broadview variety is self-pollinating, but even this variety may prove to be benefited by cross pollination.
The Persian walnut has developed in Pennsylvania and Ohio in a rather interesting pattern. Trees planted fifty to a hundred and fifty years ago managed to live and produce nuts. From these trees, seedlings were grown and planted by neighbors and friends. These trees and their seedlings in turn have now grown to producing age. Some few that produce good crops of nuts you hear about, but the vast majority are just non-producing shade trees. Until you look for them you little realize how numerous they are.
At Linglestown, Dauphin County, however, we find a striking exception to this. Here all the trees are productive. The question there is not why don't my trees produce, but is quite spirited as to who harvests the largest crop and best nuts.
About seventy-five years ago Alfred Kleopfer planted some Persian walnuts of unknown origin, but probably from Germany. He grew three trees which were planted, one beside the village blacksmith shop, one across the street, and the third at a neighbor's. One tree lived for only a short time. The blacksmith shop has been replaced by a modern dwelling but the walnut tree was saved and has grown to be a tree 6' 6" in circumference and probably 60 feet high. The one across the street is of nearly equal size but the top has been damaged by storm and the tree is not as tall.
These two trees were able to cross-pollinate and one tree was especially productive. Miles Bolton recognized its value and began growing seedling trees and distributing them to his neighbors. Some of them were quite skeptical and even refused to take them as a gift and plant them. However, he got the village pretty well planted to Persian walnut trees, so that today there are 145 nice trees within the village, and two small orchards on farms nearby.