Hickory

Hickory
Hickory at Morton Arboretum Accession 29-U-10
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Fagales Family: Juglandaceae Genus: Carya Nutt.
Species
See text

Hickory is the common name for any of the deciduous trees comprising the genus Carya of the Juglandaceae family, characterized by pinnately compound leaves, flowers in the form of small catkins, and fruit in the form a large, hard-shelled nut with an edible seed enclosed in a fleshy, four-valved husk that splits open at maturity.

pecan, shagbark hickory

Overview and description

Comparison of North American Carya nuts

Hickories (genus Carya) are members of the walnut family, Juglandaceae. Members of Juglandaceae have large aromatic leaves, which are usually alternate, but opposite in members of Alfaroa and Oreomunnia. The leaves are pinnately compound, or ternate, and usually 20-100 centimeters long. The trees are wind-pollinated, the flowers usually arranged in catkins, and the fruit is a true botanical nut.

There are eight genera in the family, including the commercially important nut-producing trees walnut (Juglans) and hickory (Carya), the later include the commercially important pecan (Carya illinoinensis). The Persian walnut, Juglans regia, is one of the major nut crops of the world. Walnut and hickory are also valuable timber trees.

The genus Carya (from Ancient Greek κάρυον "nut") includes 17 to 19 species of deciduous trees with pinnately compound leaves and large nuts. A dozen or so species are native to North America (11–12 in the United States, 1 in Mexico), and 5–6 species from China and Indochina. Another Asian species, Beaked Hickory, previously listed as Carya sinensis, is now treated in a separate genus Annamocarya, as Annamocarya sinensis.

Hickory flowers are small yellow-green catkins produced in spring. The flowers are wind-pollinated, and monoecious, with staminate and pistillate catkins on the same tree.

The fruit is a true nut in the botanical sense. That is, it is a simple dry fruit with one seed in which the ovary wall becomes very hard (stony or woody) at maturity, and where the seed remains unattached or unfused with the ovary wall. The fruit is a globose or oval nut, 2 to 5 centimeters long and 1.5 to 3 centimeters in diameter, enclosed in a four-valved that splits open at maturity. The nut shell is thick and bony in most species and thin in a few species, including C. illinoinensis (pecan); it splits apart when the seed germinates.

Species and classification

Carya cordiformis (Bitternut Hickory) foliage

Ripe hickory nuts ready to fall, Andrews, SC

In the APG system, genus Carya (and the whole Juglandaceae family) has been recently moved to the Fagales order.

North America

• Carya sect. Carya — typical hickories
  • Carya floridana Scrub Hickory
  • Carya glabra Pignut Hickory
  • Carya myristiciformis Nutmeg Hickory
  • Carya ovalis Red Hickory (treated as a synonym of C. glabra by Flora N. Amer.)
  • Carya ovata Shagbark Hickory
    • Carya ovata var. australis (syn. C. carolinae-septentrionalis) Southern Shagbark Hickory
  • Carya laciniosa Shellbark Hickory
  • Carya pallida Sand Hickory
  • Carya texana Black Hickory
  • Carya tomentosa (syn. C. alba) Mockernut Hickory

• Carya sect. Apocarya — pecans
  • Carya aquatica Water Hickory
  • Carya cordiformis Bitternut Hickory
  • Carya illinoinensis Pecan
  • Carya palmeri Mexican Hickory

Asia

• Carya sect. Sinocarya — asian hickories
  • Carya dabieshanensis Dabie Shan Hickory (may be synonymous with C. cathayensis)
  • Carya cathayensis Chinese Hickory
  • Carya hunanensis Hunan Hickory
  • Carya kweichowensis Guizhou Hickory
  • Carya poilanei Poilane's Hickory
  • Carya tonkinensis Vietnamese Hickory

Two of the most important commercial species are the pecan and the shagbark hickory.

Ripe pecan nuts on tree

Pecan. Pecan is the common name for a large, North American deciduous hickory tree, Carya illinoinensis, characterized by deeply furrowed bark and an edible, oval nut. The pecan grows to 20–40 meters in height, with a trunk up to 2 meters in diameter. The leaves are alternate, 40–70 centimeters long, and pinnate with 9–17 leaflets, each leaflet 1-2 centimeters long and 2–7 centimeters broad. The male catkins are pendulous, up to 18 centimeters long; the female catkins are small, with three to six flowers clustered together. The pecan fruit is an oval to oblong nut, 2.6 to 6 centimeters long and 1.5 to 3 centimeters broad, dark brown with a rough husk 3 to 4 millimeters thick, which splits off in four sections at maturity to release the thin-shelled nut (FNA; OBS; Collingwood et al. 1964). It is native to south-central North America, including in the United States and in Mexico.

Typical bark of shagbark hickory

Shagbark hickory. The shagbark hickory (Carya ovata) is a common hickory in the eastern United States and southeast Canada. It is a large deciduous tree, growing up to 27 meters tall, and will live up to 200 years old. Mature Shagbarks are easy to recognize because, as their name implies, they have shaggy bark. This character is however only found on mature trees; young specimens have smooth bark. The leaves are 30-60 cm long, pinnate, with five (rarely three or seven) leaflets, the terminal three leaflets much larger than the basal pair. The flowers are small wind-pollinated catkins, produced in spring. The fruit is an edible nut, 2.5-4 cm long with a green four-valved cover which splits off at maturity in the fall and a hard, bony shell.

Importance

Ecological importance

The pecan provides an important food resource for many animals, including birds (such as blue jays and crows), squirrels, deer, raccoons, and rats. Reflecting the harmony in nature, various animals also help the pecan tree, serving as dispersal agents, spreading the pecan so that it can germinate some distant from the parent tree. Blue jays are the major avian dispersal agent, while the eastern fox squirrel is the major mammalian dispersal agent (Sparks 2005).

Hickory is used as a food plant by the larvae of some Lepidoptera species. These include:

• Brown-tail (Euproctis chrysorrhoea)
• the Coleophora case-bearers C. laticornella and C. ostryae.
• Regal moth (Citheronia regalis), whose caterpillars are known as hickory horn-devil
• Walnut Sphinx (Amorpha juglandis)

Another insect that uses the hickory tree as a food source is the hickory leaf stem gall phylloxera (Phylloxera caryaecaulis). Phylloxeridae are related to aphids and have a similarly complex life cycle. Eggs hatch in early spring and the galls quickly form around the developing insects. Phylloxera galls may damage weakened or stressed hickories, but are generally harmless. Deformed leaves and twigs can rain down from the tree in the spring as squirrels break off infected tissue and eat the galls, possibly for the protein content of the phylloxera, or possibly because the galls are fleshy and tasty to the squirrels.

Culinary value

The nuts of some species are palatable, while others are bitter and only suitable for animal feed. Shagbark and Shellbark Hickories, along with the Pecan, are regarded by some as the finest nut trees.

When cultivated for their nuts, note that because of their self-incompatibility, clonal (grafted) trees of the same cultivar cannot pollinate each other. Two or more cultivars must be planted together for successful pollination. Seedlings (grown from hickory nuts) will usually have sufficient genetic variation.

The shagbark hickory nuts are edible with an excellent flavor, and are a popular food among those who know them. The trees bear too seldom for them to be grown commercially. Shagbark Hickory wood is used for smoking meat and for making the bows of Native Americans of the northern area.

For humans, pecans also are major food item, whether eaten fresh or used in preparations of other dishes, such as pecan pie or praline candy. The tree also is used for wood.

Nuts from the pecan trees are a popular food.

Commercial wood use

Hickory wood is extremely tough, yet flexible, and is valued for tool handles, bows (like yew), wheel spokes, carts, drumsticks, Lacrosse stick handles, golf club shafts (sometimes still called hickory stick, even though made of steel or graphite), the bottom of skis, walking canes etc. and for punitive use as a switch or switch (rod) (like hazel), and especially as a cane-like hickory stick in schools. Baseball bats were formerly made of hickory but are now more commonly made of ash. Hickory is also highly prized for wood-burning stoves, because of its high caloric content. Hickory wood is also a preferred type for smoke curing meats. In the Southern US, hickory is popular for cooking barbecue, as hickory grows abundantly in the region, and adds flavor to the meat. Hickory is sometimes used for hardwood flooring due to its durability and character.

Other uses

A bark extract from shagbark hickory is also used in an edible syrup that is similar to maple syrup, with a slightly bitter, smoky taste.

References

ISBN links support NWE through referral fees

• Collingwood, G. H., W. D. Brush, and D. Butches (Eds.). 1964. Knowing Your Trees, 2nd ed. Washington, D.C.: American Forestry Association, Washington, DC.

• Flora of North America (FNA). n.d. Carya illinoinensis. FNA Vol. 3. Retrieved April 13, 2008.

• Oklahoma Biological Survey (OBS). n.d. Carya illinoinensis. Oklahoma Biological Survey. Retrieved April 13, 2008.

External links

• Carya Large-format diagnostic photos, Morton Arboretum acc. 29-U-10
• Flora of North America: Carya
• Flora of China: Carya
• USDA Agricultural Research Service: Carya
• Edibility of different species' nuts, from a snack food manufacturer
• Comparison of eastern North American hickories at bioimages.vanderbilt.edu
• Comparison of hickory nuts at bioimages.vanderbilt.edu

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