Hickory

Hickory refers to a group of trees belonging to the genus *Carya*. These trees are members of the walnut family, known as Juglandaceae. Within this genus, there are 19 accepted species found in different parts of the world.

Seven of these species are native to Southeast Asia, including China and Indochina. The other twelve species are native to North America. The name "hickory" likely comes from an Algonquian word. It might refer to the nut itself or a milky drink made from the nuts. The scientific name *Carya* comes from a word meaning "nut."

Hickories are typically temperate or subtropical forest trees. Most species are deciduous, meaning they lose their leaves annually. However, *Carya sinensis* in Southeast Asia is an evergreen species. In the spring, these trees produce small, yellow-green flowers called catkins. These flowers are wind-pollinated, meaning the wind carries pollen between them. They are also self-incompatible, which means a tree cannot pollinate itself.

The fruit is a globose or oval nut. This nut is enclosed in a four-valved husk. When the fruit reaches maturity, the husk splits open to reveal the nut. Most species have a thick, bony shell to protect the seed. The pecan, or *Carya illinoinensis*, is a notable exception with a thin shell. This shell divides into two halves when the seed germinates.

There are two main sections within the genus *Carya*. One section is *Carya* section *Carya*, which contains the typical hickories. This group includes species like the pignut hickory and the shagbark hickory. The other section is *Carya* section *Apocarya*, which includes the pecans.

Within the North American group, there are many specific varieties. For example, the northern and southern shagbark hickory are varieties of *Carya ovata*. Some species, like the water hickory, grow in swampy areas. Scientists also recognize about nine different named hybrids where species cross with one another.

The history of the hickory tree spans millions of years. The oldest fossils are Cretaceous pollen grains found in Mexico and New Mexico. Modern *Carya* first appeared in the fossil record about 34 million years ago during the Oligocene.

Fossil evidence suggests the genus diversified during the Miocene epoch. In the past, hickories had a much wider distribution across the Northern Hemisphere. The Pleistocene Ice Age, which began 2 million years ago, caused the genus to disappear from Europe. In North America, the range also shrank. Hickory is no longer found west of the Rocky Mountains. Early fossils show that ancient hickory nuts had thinner shells than modern ones. This suggests that trees developed thicker shells over time to defend against rodents.

Hickory nuts are highly nutritious for both humans and animals. Dried hickory nuts consist of 64% fats and 18% carbohydrates. They also contain 13% protein and only 3% water.

These nuts are a rich source of B vitamins and minerals. They provide 220% of the Daily Value for manganese. Because of this energy density, they were a vital food source for indigenous peoples. For example, the Cherokee people used them to make Kanuchi soup. They also extracted edible oil by crushing or boiling the nuts. Some species produce delicious nuts, while others are too bitter and are used only for animal feed.

The wood of the hickory tree is quite unique. It is hard, stiff, dense, and resistant to shock. No other commercial wood offers this specific combination of strength and toughness.

Because of these traits, hickory is used for tool handles, bows, and drumsticks. It is also used for wheel spokes and walking sticks. In the past, hickory was used to build early aircraft. It is also a preferred wood for making Scottish shinty sticks. However, hickory is sensitive to moisture. It can shrink, warp, or swell when humidity changes. This is because the grain structure makes it more likely to absorb water.

Hickory plays a role in many different ecosystems and industries. Many insects, known as Lepidoptera, use the tree as a food source. This includes the Luna moth and the Regal moth.

Some insects, like the hickory leaf stem gall phylloxera, create galls on the tree. While these can damage stressed trees, they are usually harmless. Hickory is also important for cooking and fuel. Its high energy content makes it an efficient fuel for wood-burning stoves. Many people use hickory wood to smoke meats, especially in the Southern United States. The wood adds a specific flavor to barbecue. Even the bark has uses, as it can be used to create dyes or lye for soapmaking.