The Carpathian or hardy Persian walnuts (Juglans regia), as grown in Indiana, are nearly all seedling trees resulting from the desire of some hobbyists to try something new. Other than a few exceptions, most of the seedling trees were planted during the period of 1934 to 1938. Credit is due to the Wisconsin Horticultural Society in offering the seedling nuts for sale and from these plantings numerous trees grew and fruited. A few test winters, with the temperature as low as minus 20 degrees F., left only those trees hardy in wood and bud. The seedling trees under observation have been fruiting for the past six to eight years, with some trees producing as much as five to six bushels of nuts per year.
The tree grows best in well drained, fertile soil and a bluegrass sod. Small amounts of nitrate fertilizer, about the same quantity used on fruit trees, have stimulated growth and no doubt have helped in the sizing up of the nuts. The tree does not do well under cultivation or mulching, as winter injury to the tree has been recorded when compared to bluegrass sod. There is also a possibility that the tree will respond to applications of liquid or soluble nitrates when mixed in spray materials. Six walnut trees were sprayed with "Nu Green" on May 9th and May 28th, 1950, using the same mixture as is recommended for apples—five pounds per 100 gallons of spray mix. These trees were observed weekly, and by late August had made more growth and gave better response than trees in comparable unsprayed rows. As the walnut trees are of different varieties, no definite comparisons may be drawn, but the trees so sprayed outgrew the unsprayed plot, although both plots had received a spring application of fertilizer of equal amount.
Set of Fruit Depends on Pollination
The best yields of fruit are found on trees that have a good pollinator close by. Oftentimes the catkins of the Persians dry up, fail to shed pollen when the pistillate flowers are receptive or fail to produce staminate flowers. It was noted early this spring that the catkins on the Persians were very few. Pollen was gathered from the butternut (Juglans cinerea) for pollinating the pistillate flowers that opened early. The mid-season flowers were pollenized with black walnut (Juglans nigra), and the later blooms were fertilized with pollen from the heartnut (Juglans sieboldiana cordiformis). Many of the pistillate flowers were bagged and remained receptive for a long period.
The best set of fruit on trees this year is on trees that have either the black walnut or the heartnut near by as pollinizers. The pollen from the butternut seemed to dwarf the fruit size on those trees where the pistillate flowers were bagged in the Purdue planting. We have little doubt that the Persian walnut develops a preponderance of pistillate flowers and relies on pollen from kindred species for a good set of fruit.
Nut Displays Have Educational Value
The interest in the Persian walnut in Indiana has developed to the extent that several commercial fruit growers have set out small acreages. Most of the trees are seedlings from trees previously fruited, although several growers have budded or grafted the better seedlings on the native black walnut. The public has become enthused through the various displays at local and state fairs and through the state nut show now being held annually. The exhibits have brought out some very desirable seedlings, each listed under the owner's name. Some of the seedling nuts have averaged about two inches in diameter, and 12 year old trees have produced as much as 50 pounds of cured nuts.
The largest Persian walnut tree found in Indiana is at Lafayette, it being 12 inches in diameter and possibly 40 feet high. This tree has been fruiting for the past 15 years. There are probably five or six bushels of nuts on this large tree at the present time. This tree was placed as a yard tree for its ornamental value and for the fruit.
Numerous persons have inquired about the Persian walnut as a specimen tree in their landscaping program and the demand far exceeds the supply. As many of the elms, oaks, and some chestnuts are going out from disease troubles, the Persians may be used as a replacement. The food value of the walnut compares very favorably with that of other native nuts, according to Dr. A. S. Colby, of the University of Illinois.
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% Water % Protein % Fat % Carbo- % Ash No. Calories
hydrate per Pound
Persian walnut 2.8 16.7 64.4 14.8 1.3 3305
Black walnut 2.5 27.6 56.3 11.7 1.9 3105
Hickory nut 3.7 15.4 67.4 11.4 2.1 3495
Pecan 3.0 11.0 71.2 13.3 1.5 3633
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