Hickory Trees

Joyce Starr
Hickory grove

If you are looking for a nut-producing tree that's sturdy and makes a stately impression in the landscape, then look no further than a hickory tree. Whether you desire to feed the wildlife or yourself, there's a hickory to fit your taste.

A Family Divided

All hickories belong in the family Carya with the family divided into two major groups: true hickories and pecan hickories. Common species in the true hickory category include shagbark (Carya ovata), pignut (Carya glabra), shellbark (Carya laciniosa), and mockernut (Carya tomentosa).

Of the pecan hickories, the best-known species is pecan (Carya illnoinensis) and is the only hickory that produces nuts having a commercial value. There are over 1000 different cultivars with the major difference being the size, shape, characteristics of the shell, taste, and ripening date of the nuts. Another pecan hickory is the bitternut (Carya cordiformis).

Basic Characteristics of Both Groups

All types are native to eastern portions of the U.S., deciduous and produce nuts. Compared to other hardwood trees, hickories are slow-growing, with pecan the fastest growing species.

These are large trees obtaining a mature height from 60 feet to over 100 feet and the canopies can be as wide as the tree is tall. All types have green, oblong leaves that change color during the fall months.

Hickory bark

They generally have one major trunk with grayish to brown bark that develops deep ridges and grooves as it ages and can peel. These are long-lived trees, with an average lifespan of 300 years and producing nuts for most of that time.

The trees produce male flowers, which are green to yellowish long catkins in springtime, and pollination occurs through the wind. Small clusters of female flowers appear on spikes and after being pollinated, fruits appear throughout summer, ripening in autumn.

Male flowers
Male flower, split husks and leaves
Female flower
Female flower and leaves

Differences Between Groups

All types of hickories resemble each other in the look, shape and size of the tree. Looking at the leaf structure helps in distinguishing true hickories from pecan hickories. The leaves on true hickories have five to nine leaflets that are oppositely branched. However, pecan hickories leaves have nine to 17 leaflets that are oppositely branched.

Another way to distinguish the difference between the two types is by inspecting the size and shape of their nuts. A thick, woody shell surrounds all types of hickory nuts, with some types splitting more easily than others do. Shape of the shell can be round like the pignut hickory or more of an oblong shape such as the pecan. All types of hickory nuts are edible, but some are bitter to the taste and some are sweet.

Pecans
Pecans
Shagbark
Shagbark

Characteristics by Type

Each type of hickory has subtle differences from the other whether it's the nut or size of tree.

  • Shagbark hickory is hardy throughout USDA zones 4 through 8 and averages 70 feet tall at maturity. It grows best in rich, moist soil that drains well and in full to partial sun. Encased in a thick hull, the oval nuts open to reveal a sweet treat. The tree starts producing nuts around 40 years of age.
  • Pignut hickory is hardy in USDA zones 4 through 9 and averages 80 feet tall at maturity. This hickory performs best grown in rich soils that drain well but kept moist and in full sun to partial sun. Pear-shaped nuts have thin husks that give way to bitter fruits suitable for wildlife. The tree doesn't start producing nuts until around 25 years old.
  • Shellbark hickory is hardy in USDA zones 5 through 8 and averages 80 feet tall at maturity. The tree grows best in rich, moist soils that drain well, though the tree tolerates periodic flooding. Preferred light conditions are sunny to partial shade. The tree is sometimes called king nut hickory because its round, sweet nuts are the largest in the hickory family. Shellbark hickories start producing nuts around 40 years of age.
  • Mockernut hickory is hardy throughout USDA zones 4 through 9 and at maturity averages around 80 feet tall. The tree performs best in rich, moist soils that drain well and in full sun to partial shade. Round nuts are sweet and the tree starts producing nuts when around 25 years old.
  • Pecan hickory is hardy in USDA zones 5 through 9 and at maturity averages around 130 feet tall. It grows best in rich, moist soils that drain well and in full sun to partial shade. The oblong nuts are sweet and trees typically start bearing nuts at seven years.
  • Bitternut hickory is hardy throughout USDA zones 4 through 9 and averaging around 80 feet tall at maturity. The tree performs best in rich, moist soils that drain well and in a sunny to partially sunny location. The rounded nuts are bitter as the name suggests and trees start producing around 25 years of age.

Landscape Uses

Hickey Tree With Golden Leaves

All hickories require a large space in the landscape to accommodate their height and width, so select a location where the tree won't interfere with structures or power lines. Hickory trees work well used as eye-catching specimens or shade trees. Due to their long taproot, when planting, select a permanent location, as the trees do not transplant well.

Like black walnuts, all types of hickories contain the substance juglone, which is toxic to many plants growing under or close to them. Plants affected by the substance show signs of wilting, decreased growth, and death. To play it safe, plant any new plantings at least 80 feet from the hickory.

The trees work well used in wildlife or native gardens with the nuts feeding a host of wildlife such as squirrels. Throughout the autumn months, all types of hickories brighten the landscape with their colorful foliage.

Purchasing Considerations

When purchasing any type of hickory tree, inspect the tree for signs of pest or disease problems. Do not purchase trees with discolored or deformed foliage or has outgrown its nursery container, showing signs of roots growing out of the bottom drain holes. Hickories with wrapping roots sometimes never grow properly once planted in the landscape.

You can probably find a hickory tree that is native to your area at your local nursery; however, many online nurseries sell common hickories such as shellbark, shagbark and pecans. Check online retailers such as Arbor Day Foundation, Willis Orchard Company, and Go Native Tree Farm. Most trees you purchase online or at a local nursery are around 1-year-old or younger and shipped bare rooted and 4 to 6 feet in height.

How to Plant

Properly planting your hickory tree assures it gets off to a good start and healthy growth. Remember, all hickories grow into large trees so make sure to allow at least 35 feet of unobstructed space on all sides of the tree, when selecting a location and the site receives full sun to partial shade throughout the day. For optimal growth, plant hickories during fall and early winter.

  1. Prepare the planting site by removing all grass and weed growth, clearing an area that is approximately 3 feet in diameter.

  2. Dig a hole that is as deep as the container the hickory is growing inside or as deep as the root system, if planting a bare root tree and slightly wider. Do not add fertilizer or amendments to the hole.

  3. Remove the hickory from its nursery container and gently tease the roots apart.

  4. Place the root ball into the prepared hole and gently spread the roots out around the hole. Make sure not to plant too deep and the grafted area on the bottom portion of the trunk is at least 2 inches from the ground.

  5. Fill the hole half-full of soil and then apply water to remove any air pockets. Finish filling the hole with soil and gently tamp down with your foot. Water the area, thoroughly saturating the roots.

Care Requirements

Besides needing a large space to grow, fertile, moist soil that drains well, all hickories require regular applications of water, fertilizer and pruning for healthy trees.

Irrigation

Unless weather conditions are rainy, all types need weekly applications of water to grow properly, especially when conditions are hot and dry. Newly planted trees need watering immediately after planting and once to twice weekly until the tree establishes itself in the planting site approximately eight to 12 weeks later.

Fertilizer

Trees that haven't started bearing nuts require 1 pound of 10-10-10 fertilizer for each year of age and applied in late winter. Do not exceed 25 pounds per tree yearly. Trees that are bearing nuts require 4 pounds of 10-10-10 fertilizer for each inch of the trunk.

Spread the fertilizer evenly under the hickory's canopy, not allowing the product to butt against the trunk. Water the fertilizer into the soil after applying. Keep the area under the tree free of grass and weed growth as the unwanted vegetation can rob the tree of the needed nutrients and water. It also cuts down on trunk injuries due to lawn equipment bumping into the tree.

Pruning

Prune trees to remove damaged, dead, diseased, or crossing limbs anytime throughout the year. Cutting off low-hanging branches close to the trunk allows easy access under the tree's canopy. Doing heavy pruning of the tree can delay the production of nuts for up to three years. Always use sterilized pruning tool blades to cut into the wood so you don't transfer disease to the tree.

Harvesting and Storing Hickory Nuts

Depending on the type of tree, hickory nuts begin ripening in September through fall. The outer husk of ripe nuts changes from green to brown and may begin splitting into sections revealing the nut. Allow the nuts to ripen on the tree before harvesting. If picked while the husk is green, the inner meat never ripens. Hickory nuts are ready for harvesting when you notice them falling onto the ground.

  1. Retrieve freshly fallen nuts off the ground and by shaking branches with a long pole.
  2. Place the hickory nuts into a tub of water and toss the ones floating on top as this shows weevils are present or the meat isn't formed.
  3. Spread the hickory nuts out in a thin layer in a location that's dry, cool, and with good circulation of air. Due to animals stealing your bounty, you probably don't want to dry the nuts outdoors.
  4. Allow the nuts to dry for two weeks.

Store them in the shell or shelled in a cool area or inside the refrigerator or freezer.

Common Diseases

Some of the common diseases affecting trees and methods of prevention and control include:

Pecan Scab

Pecan scab

A very destructive fungus affecting hickories and is especially damaging to pecan trees and the production of nuts. The problem generally occurs during a wet and humid growing season, tapering off as the seasons continue, only creating cosmetic damage to nuts.

When damaging, pecan scab shows up on the newer growth of twigs, foliage and nuts, covering the affected areas with rough or velvety feeling black spots. Keeping the area clean under the tree, making sure air circulates and keeping any limbs hanging to the ground pruned off, helps in preventing problems. Preventative applications of the fungicide mancozeb sprayed every other month helps control a scab breakout. Thoroughly spray the tree with the fungicide as soon as you notice the problem and repeat every two weeks for three months.

Galls

Galls form by various fungi enter the tree, usually through a wound in the bark. Round, dark lesions appear on the branches and can form clumps. No treatment is necessary and the galls only create cosmetic problems. If left on the affected branch, galls will eventually kill the affected wood.

Measures for control include good care of the tree and avoiding injuring the bark. Make sure the hickory is properly watered and fertilized to keep it growing at its best. Prune off limbs with galls present, being sure to trim several inches back into healthy wood. Keep the area under the tree free of fallen nuts and debris.

Powdery Mildew

Powdery mildew is easy to identify because the fungus covers the leaves, stems, and buds in a white, powdery substance that usually appears out of nowhere. Warm, humid, and wet weather are prime conditions for an outbreak of the problem.

Treat the hickory with a copper fungicide, when an occurrence of powdery mildew happens during the growing season, and reapply two weeks later. There is no need for a fungicidal treatment when powdery mildew happens late in fall and winter.

Various Leaf Spots

Hickory trees are susceptible to various types of fungi causing spots on the foliage. The basic difference in the spots is the color. Spots can be yellowish, brown or rust-colored, with the darker spots seeming to affect the lower portion of the foliage.

There is no need to treat the tree because at worse, the affected leaves may drop. Prevent the problem by keeping the area under the tree free of all fallen debris.

Pest Problems

Pests can create problems for the hickory's foliage, blooms, and nuts.

Aphids

Aphids are small, pear-shaped sap-sucking insects that are usually yellowish in color. A close inspection of the foliage, especially new shoots, show mass congregation of these insects and sometimes you'll notice a stream of ants traveling up and down the limbs traveling to the aphids. Ants milk the aphids of the honeydew they produce, which can then lead to the black fungus sooty mold that drops onto the foliage covering it in a black substance.

Aphids suck juices from the hickory's foliage, which then leads to curling and discoloration of the leaves. An aphid attack usually isn't life threatening to the tree, but if the landscape doesn't have enough predators such as parasitic wasps, a treatment of insecticidal soap is necessary. Spray the entire plant with the product, being sure to saturate the undersides of the foliage. Repeat weekly as needed. Wash large outbreaks of sooty mold from the foliage with a strong stream of water or wiping the leaves with a damp cloth.

Bark Beetles

Bark beetles can appear throughout the year especially when conditions are warm, but springtime is their most active time of year and when you may notice their activity. The small, brown rice-sized insect bores holes through the hickory bark to lay its eggs and then bores through the cadmium of the tree. You might also notice what looks like highways bored into the tree's outer bark. Once the tree is infected control is almost impossible, but prevention is the most important step one can take.

The beetle rarely seriously affects healthy hickories, so making sure the tree is properly watered and fertilized is the best course in preventive action. Before the beetle infests the tree, spray the trunk with a pyrethroid-based insecticide and repeat every couple of weeks to keep adults at bay. If you notice a beetle infestation on the branches, prune off the affected branch, being sure to cut several inches back into healthy wood.

Spittlebugs

Spittlebugs are small winged insects that rarely reach over 1/4-inch in length and range in colors of greenish to brown and gardeners will rarely notice them. A telltale sign of a spittlebug infestation is what looks like areas of spit congregated on the foliage, stems and buds. The major damage they cause is distortion of the foliage and isn't life-threatening to the hickory. Control is a simple as spraying the infected areas with a strong blast of water. Keep the area under the hickory clean of any fallen debris.

Pecan Weevil

Pecan weevils overwinter in the ground under the hickory tree and usually emerge during late summer crawling up the tree and attacking the unripe nuts by laying their larvae inside. If left unchecked, the weevil larvae destroy a nut harvest.

Prevention is the best course of action in preventing a weevil infestation. Clean up all fallen nuts and debris from the ground beneath the tree. In early summer, apply an insect barrier to the trunk, such as Tanglefoot, which keeps the weevils from climbing up the tree and getting to the ripening nuts. For further prevention, spray the entire tree's foliage and nuts with a product such as Sevin and repeat as the package recommends, which is generally every two weeks. This should kill any insects that have gained entry to upper portions of the tree.

General Prevention and Treatment of Problems

Several pests and disease problems affect all types of hickories. Keeping the area under and around the tree free of unwanted growth and fallen debris goes a long way in keeping trees healthy as well as adequate air circulation around trees.

When using any type of fungicide, insecticide, or other products to treat problems, make sure you fully cover both sides of the foliage and all portions of the tree for the best control.

More Than a Shade and Nut Tree

Hickory trees offer so much more than just being a large, majestic tree casting shade and a good supply of nuts. Any healthy limbs pruned from the tree should be dried and used in the grill or smoker to enhance the food with a delicious smoky taste.

Hickory Trees