Carya

( KAIR - yuh )

At-A-Glance Information

Commonly known as Hickory, this genus of trees is native to China, Indochina, Mexico, the United States and Canada. Some species are cultivated for their edible large nuts, and others are grown for lumber. These are temperate forest trees, and produce insignificant greenish-yellow flowers in springtime. Foliage is pinnately compound and green, turning yellow-gold in fall before leaves drop. Trees grow at a rate of between 12-24 inches per year, reaching heights of 60-100 feet when mature with a spread of 40-60 feet. These are important shade trees in previously wooded areas, and are also used as ornamentals, valued for their brilliant fall colors and ability to withstand periods of drought.

Carya Species and Varietals

The genus Carya includes about 18 species, and is a member of the plant family Juglandaceae. The common name for these trees, Hickory, is derived from the Algonquin or Powhatan language, pockerchicory/pocohicora, referring to the nuts. The best growing zones for these trees vary depending on the species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Carya aquatica (Bitter Pecan, Water Hickory, Swamp Hickory, Bitter Water Hickory)
These large trees reach over 100 feet tall when mature, and are aggressive spreaders via seed. Their native range is the Atlantic and Gulf Coastal Plains in the southeastern United States. This species is occasionally used as a shade tree, or cultivated for timber to make firewood or fenceposts. This species grows well in USDA hardiness zones 5-9

Carya cathayensis (Chinese Hickory, Shanhetao)
This species of Hickory tree is native to China, and is a slow-grower, eventually reaching 65 feet tall. These trees prefer growing on mountain slopes, in valleys, and along riverbanks in their native range, and produce edible nuts that are commonly eaten peeled and roasted. Chinese Hickory trees grow well in USDA hardiness zones 5-9.

Carya cordiformis (Bitternut Hickory, Yellowbud Hickory, Swamp Hickory)
This large Pecan Hickory reaches 115 feet tall when mature, and produces wind-pollinated catkins in springtime. Fruits are very bitter nuts with hard shells and green covers. Winter buds are bight sulfur-yellow. The nuts are not edible. These trees are native to moist mountain valleys in the eastern United States, and are mainly cultivated for lumber and pulpwood.

Carya floridana (Scrub Hickory, Florida Hickory)
This species is native to central Florida, and reaches up to 80 feet tall. It forms a multi-trunked tree with green leaves. Edible seeds are sweet, and are favorites of many native animal species in the plant's natural range. These trees grow well in USDA hardiness zones 9 and 10.

Carya glabra (Pignut Hickory, Pignut, Coast Pignut Hickory, Smoothbark Hickory, Swamp Hickory, and Broom Hickory)
This species of Hickory is native to the eastern United States and Canada, and produces pear-shaped nuts that ripen in September and October. The fruits have a sweet maple smell. Foliage turns yellow-red in fall before leaves are shed. These are commonly seen shade trees in wooded suburban areas in its native range, but is seldom planted as an ornamental landscape tree due to its size and difficulty of transplanting. This species grows well in USDA hardiness zones 4-9.

Carya illinoinensis (Pecan)
These trees are widely cultivated and harvested for their edible nuts, which are used as a snack, in various recipes, and most famously in pies and candies. The Pecan is the state nut of Alabama, Arkansas, California, Texas, and Louisiana. It is the state tree of Texas. This species grows well in USDA hardiness zones 5-9. Trees reach between 66 and 131 feet tall when mature, and reach 16 feet tall in 10 years. These trees are best in very large gardens, where they can reach their full size. Most Pecan cultivars will continue to set light crops in the absence of pollination, but harvests will be heavier with a Type 1 and Type 2 cultivar planted close to each other. Popular Type 1 cultivars include 'Western Schley', and 'Pawnee' and commonly grown Type 2 cultivars include 'Mohawk', 'Burkett', and 'Wichita'.

Carya laciniosa (Shellbark Hickory, Kingnut, Bottom Shellbark, Western Shellbark)
This species of Hickory produces the largest nuts in the genus, and is difficult to transplant due to its large taproot. Seeds are edible, and are commonly consumed by wildlife in the tree's native range (north-central United States). Shellbark Hickory grow well in USDA hardiness zones 5-9, and are considered rare in the wild, due to human development and other activities.

Carya ovata (Shagbark Hickory, Shellbark Hickory, Scalybark Hickory, Upland Hickory)
This species is native to the eastern United States and southeastern Canada, and reaches well over 100 feet tall when mature. Bark on these trees is shaggy and brownish-grey. Nuts are edible, favorited among both humans and squirrels for their excellent flavor. These trees are unsuitable for commercial production, however, given their unreliable output and sheer size. An extract from the bark of these trees is used as an edible syrup similar to maple syrup.

Carya palmeri (Mexican Hickory)
These trees are native to the steep slopes of the mountains of eastern Mexico, and were first described by American horticulturalist and botanist Wayne Eyer Manning. Leaves are covered with scales and bark is whitish. Nuts have thin shells. Trees reach between 50 and 65 feet tall when they are mature.

Carya texana (Black Hickory, Texas Hickory)
These trees are known for their dark colored bark, and are endemic to the southeastern United States. This species reaches up to 135 feet tall when mature, and bark has a tight diamond pattern to it. Leaves are typically covered in scales that make them look rusty brown. Nuts are bronze to reddish brown and the seeds are sweet and edible, though sometimes a bit bitter. Black Hickory grows well in USDA hardiness zones 5-9.

Carya tomentosa (Mockernut Hickory, Mockernut, White Hickory, Whiteheart Hickory, Hognut, Bullnut)
This species of trees is the most abundant in the genus, and is native to the eastern half of the United States. They grow well in USDA hardiness zones 4-9. These trees can reach up to 500 years old, and have strong, hardy, and flexible wood. Foliage yellows in fall before leaves drop. This species is not cultivated for its nuts.

Caring for Carya

Choose a spot in the landscape that gets full sun (at least six hours per day). These trees can tolerate partial shade, but full sun really is ideal for healthy growth. Ensure that soil is well-draining before planting. Hickory trees can grow in a variety of soil types, including sandy, loamy, and clay. They thrive in slightly acidic to neutral soil (with a pH of between 4.8 and 7.3). These trees form deep taproots, helping them to access deeper layers of soil in times of drought, and also stabilizing the tree. Ensure that roots will have enough space to grow downwards and outwards. Hickory trees do not require fertilizing.

Mulch around the base of the tree after installing, keeping the layer a few inches away from the trunk. Prune sparingly; Hickory trees really do not need pruning, unless there are damaged, dead, or diseased branches. Pruning in late winter or early springtime before new growth pushes out for the year is best. Avoid doing heavy prunings, as this will stress out the tree and make it susceptible to pest and disease issues. Prune young trees to establish a strong structure, removing any weak or crossing branches to prevent future problems. Stake young trees to support them as they grow; they are generally slow-growing, and will put on about a foot of growth per year. Carya trees can last for up to 200 years in the landscape if given adequate space and cared for properly.

Harvesting Carya (Hickory and Pecan)
Hickory trees grow relatively slowly, and will not begin producing full harvests of nuts until they are between 20 and 30 years old (though this depends a bit on the species grown). Many hickory species are self-pollinating, but having multiple trees planted close to each other can still boost harvests and also has the benefit of increasing the genetic diversity of seedlings. Each year, trees will produce a harvest of nuts, with about every third year producing a bumper crop. The nuts are sweet, buttery and dense, reminiscent of mild walnuts. To harvest nuts:

In autumn nuts will fall from trees that are not sheltered by larger trees, and for trees within stands branches may need to be shaken to release them. Check the ground under trees for intact nuts that are relatively unblemished and have no rotten spots. Ideal nuts will have a brownish-gray husk and the interior shell will be a rich, chestnut brown color. As you harvest, remove outer husk and drop them back on top of the soil under the tree.
Bring the nuts indoors, and place them in a bucket of water. If any of the nuts float, toss them in the garbage or compost. Then, lay the nuts out in a warm area for a few weeks to dry. They can be stored in a cool, dark, dry area (like a basement or root cellar) for up to a month.
Shelling hickory nuts is notoriously difficult, but the reward is worth the work and if you're strategic, it can go relatively quickly. There is a septum that divides the kernel, and if a nut is struck near its stem end (about 1/3 of the way down) on the septum (ridged part of the casing), it will cause the casing to fall apart more neatly. If hickory nuts get shelled, their meat can be stored in the freezer for months.

Propagation

Carya trees are best propagated by seed:

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a bag or sack, a sealable plastic bag or other container, sand, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed pods on Carya plants are pretty easy to spot, they're large and dangle from the branches. They will fall from the tree in autumn. Once they have dried out and begun to split open, you can harvest the seeds inside. Gather as many as you can into a bag, and place the bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Place your seeds in lukewarm water. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float. Carya seeds need to be cold-stratified before sowing by placing them in a sealable plastic bag or container filled partially with moistened sand. Push them down about an inch into the sand and cover.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 30-60 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.