There are six types of walnut trees in the United States, each having a specific geographical distribution. Walnut trees have long been valued for their fine-grained wood and the delicious nuts they produce. The American walnut trees differ in such features as height, the appearance of their leaves and the size of the walnut the flowers eventually turn into.
Black walnut has the largest range of native walnuts in the U.S., with the tree growing in the wild in most of the eastern half of the country. It is also the tallest of the walnuts in this country, growing as high as 100 feet. Black walnut has compound leaves, with each stem as long as 2 feet and featuring as many as 23 narrowed leaflets. The fruit, encased in a round green husk and growing in clusters, ripens by midfall and tumbles from the tree. The casing has a brown dye that will stain the hands when touched.
Butternut is another prominent walnut, often call white walnut. Butternut is in the northeastern quadrant of the United States and does not match the black walnut in height, with a 60-foot butternut tree being a huge one. The compound leaves possess from 11 to 17 leaflets, but the entire length of the stem can exceed 30 inches. Not as plentiful as black walnut, the butternut tree has oval nuts about 2.5 inches long, with a green-brown protective husk that exudes a yellowish dye. The nut itself is quite oily; it was common practice at one time to boil them to extract the oil, which then served as butter.
Four regional types of walnut trees grow within U.S. borders. The California walnut of the coastal area of that state grows to 50 feet and has the compound leaves all walnuts possess, with between 11 and 15 leaflets. It produces a small nut, less than an inch in diameter, within a dark brown husk.
Arizona walnut, which grows from Arizona through western parts of Texas, can make it to 50 feet high but is more often a shrub. The grooved nuts develop in a thin-husked shell.
The Hinds walnut favors moist soil in northern California and southern Oregon, and sometimes exceeds 50 feet in height.
The little walnut, a tree of Texas and Oklahoma, is shrub-like, with the tallest about 30 feet but most growing in the form of a multi-stemmed bush. The walnuts are predictably small, averaging half an inch wide.