What is western persimmon?

Question

I saw western persimmon in Leaves of Grass by the 19th-century American writer Walt Whitman. If you google it, you realize that American persimmon is also called common persimmon and eastern persimmon. But you cannot find anything about western persimmon. So What is this kind of persimmon really?

Over the growing sugar—over the yellow-flower'd cotton plant—over the rice in its low moist field;
Over the sharp-peak'd farm house, with its scallop'd scum and slender shoots from the gutters;
Over the western persimmon—over the long-leav'd corn—over the delicate blue-flower flax;
Over the white and brown buckwheat, a hummer and buzzer there with the rest;
Over the dusky green of the rye as it ripples and shades in the breeze;

Answer 1

I suspect that the "western persimmon" in this case is merely poetic license for a persimmon growing in the west, or western United States, as Whitman was an American poet who flourished in the mid-nineteenth century.

However, on the off-chance that he is referring to a specific variety of persimmon, I have located one other reference to "western persimmon." That reference is in a book published by the United States Department of Agriculture's Division of Plant Exploration and Introduction. In the 1930s, that division was responsible for researching and importing various foreign plant materials, with the aim of introducing hardy stock to the U.S. The imported plant materials (seeds, nuts, etc.) are inventoried in a serial publication with the lengthy name Plant Material Introduced by the Division of Plant Exploration and Introduction, Bureau of Plant Industry.

Inventory No. 114 of that serial, covering January 1 to March 31, 1933, documents the following fruits:

102112 to 102114. Diospyros kaki L. f. Diospyraceae. Kaki persimmon.

From an orchard near the village of Lienhualing, east of Peiping. [In 2019, the city formerly Romanized as "Peiping" is Romanized as "Beijing."]

102112. Hsi Yang Shih Tzu, or western persimmon. A variety not very commonly grown in this region.
102113. Hua Shih Tzu, or fire persimmon. So-called from its deep-red color.
102114. Ta Kai Shik, or large persimmon.

Again, however, I think my first inclination is correct, and "western persimmon" is mere poetic turn of phrase.