Carya species, hickory, native throughout the eastern, midwestern and southeastern United States, are seldom available in retail commerce. Primarily relegated to the deciduous forests, commingled with oak, beech, maple, tupelo and birch, few trees are more beautiful in autumn when aglow with the late developing, long persistent, rich yellow-gold foliage. Foliage shows significant frost/freeze tolerance in the range 24 to 28°F. I noticed hickories retaining fall color when adjacent species lost color or defoliated. From swamps (Carya aquatica) to mountaintops (Carya ovata) and sites between, a hickory resides. The nuts nourish all manner of wildlife and the pecan, Carya illinoinensis, is a major commercial tree, particularly in the southeast and southwest. There are ~18 Carya species and several hybrids. Eleven species occur in the U.S. with five of these extending into Canada. For a complete list of species worldwide, search germplasm research information network (www.ars-grin.gov) and plants of the world (powo.science.kew.org).

Leaves, flowers, and fruits

Hickories are tricky to correctly identify (ID), and hybrids make the process even more confusing. The following characteristics will lead the reader to the genus. After that, ID may become less clear/absolute. Leaves are alternate, compound pinnate with a central axis (rachis) and (3)5 to 19(21) leaflets, the terminal leaflet often the largest and obovate in outline; the lower leaflets oppositely arranged along the rachis. The leaf margins are serrate (toothed), surfaces pubescent or glabrous, and when bruised or crushed release a pungent odor.

Flowers are monoecious, meaning in separate structures on the same plant. Flowers open with the leaves, usually around mid-April in the Athens area (zone 8a). Male flowers appear in long cylindrical catkins from buds of the previous season’s growth. The apetalous female flowers occur on the emerging shoots of the season, either solitary or up to 10 in a cluster. The nuts that follow develop from a single ovary with two stigmas, the seeds appearing as two but joined at one end.  The top-shaped, rounded, to ellipsoidal (pecan) shaped nuts are covered with a husk that typically splits along four suture lines. Fruits mature in October-November and the dehisced nuts are often evident under the tree. The seeds are high in unsaturated oils and serve as an important food for wild animals and birds. Pecan, C. illinoinensis, is an important commercial nut tree with a value of over 399 million in 2020.

Bud, stem, bark and wood

Winter buds vary from species to species and are described within the species’ descriptions that follow. Bark is likewise variable and the shaggy bark of C. ovataand C. laciniosa, is instantly recognized. Carya glabra and C. tomentosa are smooth barked in youth, developing ridged and furrowed bark with maturity. Tree bark of Carya aquatica is smooth in youth, then slightly roughened/scaley in old age. The wood of hickories is used for furniture, flooring, cabinets, veneer, tool handles, and for smoking meats. How many hickory trees have suffered because of ham and bacon? Worth mentioning from an identification standpoint that the stems of Caryahave solid pith, while Juglans (walnuts) have chambered pith. Split the first-year stem through the center longitudinally and the differences become obvious. Both reside in the Juglandaceae family and can be confused.

Propagation of Carya is principally by seeds and grafting/budding. The latter a common method for cultivars of pecan. Squirrels may be the best seed dispersal agents, for seedlings, particularly pecans, appear weed like in the southeast. I collect nuts in October-November, place several in well drained, bark medium in 3-gallon containers, cover 1 to 2”, and protect from animals with a screen. Seedlings require a cold period and are left outside. Germination takes place the following spring. The individual seedlings are then transplanted during the next winter to 3-gallon containers, the tap root pruned to half or more its length. I know a nursery that roots cuttings of Carya aquatica by harvesting juvenile shoots that develop after transplanting trees from the field. The holes are not filled, and adventitious shoots develop from the severed roots that remain at the edges. This method could be applied to other Carya species.

Carya species are adapted to wet (Carya aquatica), sandy/dry rocky slopes and ridges (Carya tomentosa), and silt loam to clay (Carya glabra, Carya laciniosa, and Carya ovata). If they were easy to transplant, hickories would be available in greater numbers. Hickories are essential components of the North American deciduous forest ecosystem and, with oaks, maples, birches, tupelos, elms, walnuts, tuliptree, beech, and sweetgum, command and deserve to be planted and preserved.

I recommend purchasing small bare-root seedlings or containerized material. Several growers/retailers from whom I purchased hickories and other native trees include Superior Trees, Lee, FL (superiortrees.net), Mail Order Natives, Lee, FL (mailordernatives.com), Forrest Keeling Nursery, Elsberry, MO (fknursery.com). Hillis Nursery Company, Inc., McMinnville, TN, (hillisnursery.com) offers six Caryaspecies. Melanie Wells, Mount Vernon, provided additional online nurseries that supply Carya species (americanheritagetrees.org and whitehousenatives.com).

The best adapted and available Carya species for garden and native plantings include the following.

They are presented by bud and leaf characteristics. Carya aquatica, C. cordiformis, and C. illinoinensis have valvate terminal buds meaning the bud scales meet at their edges but do not overlap, the terminal larger than the lateral buds. The leaflets, the same size throughout.

Carya glabra, C. laciniosa, C. ovata, and C. tomentosa with bud scales overlapping. Leaflets fewer, the terminal leaflet larger than the laterals, often 2 to 3 times. Terminal buds larger than laterals.

Carya aquatica, water hickory, is a beautiful tree with finer textured foliage and branching habit than those that follow. There are typically 9 to 11, 2 to 3” long, equal sized leaflets. Leaves are rich green, turning soft to bright yellow in autumn. I noticed leaves still persisting on trees in Athens as late as mid-November. The nut is 1 to 1 ½” long, broadly ovoid, and four-winged along the seams. The kernel is bitter. The rich brown bark develops scaly plates, not as prominent as those of C. laciniosaand C. ovata. I noted a 70’ high tree at the Coker Arboretum, University of North Carolina, Chapel Hill. National champion is 97’ by 62’. Common in swamps and along rivers from Virginia to Texas. This has been the easiest hickory to transplant balled-and-burlapped. Zone 6 to 9.

Carya cordiformis, bitternut or swamp hickory, has seldom crossed my path, although native to every state (except Maine) east of the Mississippi and nine contiguous states west of the mighty river.  I remember trees at Middlebury College, Vermont, University of Illinois, Champaign-Urbana, IL, and in June 2022, Mount Vernon, VA. Initially, I was not positive about the identification of the Mount Vernon Carya, until Melanie Wells, horticulturist, sent a photo of the sulfur yellow buds. The branches were so high, I could not accurately count leaflet numbers (typically 7 to 9, ~equal size) or determine bud color. Melanie mentioned that the tree was previously identified as C. tomentosa. The light green, slightly falcate leaflets are 3 to 6” long, ¾ to 21/2” wide, turning rich golden yellow in fall. The suborbicular nut is 11/4” long, 4-winged or ridged, often only above the middle, the seed bitter. Typically, a slender tree with an irregular, cylindrical crown of stiff ascending branches, widest at the top. This habit description could be superimposed on the Mount Vernon specimen. Bark is gray-brown, smooth initially, developing low narrow interlacing ridges, occasionally with a few scales. I estimate 50 to 75’ high, slightly less in spread. National Champion is 106’ high and 100’ wide. Considered the fastest growing of the hickories. In the wild, most often found in low woods, less frequently in uplands, although the USDA profile describes it being found on rich, loamy or gravelly soils, low wet woods, borders of streams, and dry uplands.  Zone 4 to 9.

Carya illinoinensis, pecan- Although not native in Georgia, it is major cultivated nut crop with a value of 182.5 million in 2021. Seedling trees are like mushrooms and appear everywhere, producing reasonable quantities of edible nuts. The modern pecan industry relies on improved cultivars and thousands of acres were planted in the last 10 to 15 years. Leaflets vary from 11 to 17, each 4 to 7” long, 1 to 3” wide, the midvein slightly curved, resulting in the term falcate. About the easiest Carya to identify by foliage. Leaves are lustrous dark green, persisting late into November (Athens), occasionally with a wisp of yellow fall color. The thin-shelled, ellipsoidal, brown nuts, tapered at their ends, average 1 to 2” long and are held in a four-valved, winged, dehiscent husk. Nuts dehisce in November in the Athens area and can be readily gleaned. Plant in moist, well drained, deep soil, although stray seedlings take hold under myriad conditions.  The lateral buds resemble toasted almonds in shape and color. They are held at 45-degree angles to the stem. Bark is gray-brown, somewhat scaly on mature trunks. A large tree, 70’ and beyond, and certainly not for small properties. National champion is 97’ by 106’. In nature, the species inhabits low areas along water courses from Indiana to Texas. Zone 5 to 9.

Carya glabra, pignut hickory. I grew up with this species in southern Ohio where it was quite common. It has a tapering trunk and a regular, open, oval head of slender contorted branches. Finer texture than C. laciniosa, C. ovata, and C. tomentosa. Leaves are composed of 5 to 7 (typically 5), lustrous dark green leaflets. Each 3 to 61/2” long, 1 to 2” wide, the lower pair one-third the size of the terminal. Leaves turn beautiful golden yellow in fall. Nuts are subglobose, ¾ to 11/4” long, the seeds with a bitter taste. The bark is smooth, gray-brown on young trees, eventually developing rounded ridges, intersecting to form a diamond shaped pattern. Landscape size approximates 50 to 60’ high and 25 to 35’ wide although the National Champion is 149’ by 75’. Common in nature in drier habitats, upland soils, and rocky areas. Zone 4 to 9.

Carya ovata, shagbark hickory, is one of my favorite Noble Trees which should be planted in every park, golf course, open area from Canada to Florida and west to Missouri and Texas. The bark, composed of gray-brown shaggy scaly plates, free at both ends, curving away from trunks, makes for easy identification. The deep green leaves, comprised of five, rarely seven, 4 to 6” long, ½ to 21/2” wide leaflets, turn saturated golden yellow to golden brown in fall. Nuts, nearly round, 1 to 11/2” diameter, shell angled, husk ¼ to 1/3” thick, freely splitting at maturity, no winged suture lines, enclose edible, sweet seeds. Shelled shagbark hickory nuts sell for $9.99 per ounce or $19.99 dollars for three ounces from hickorynutsdirect.com. Species develops a straight, cylindrical trunk, with an oblong crown of ascending and descending branches (like C. laciniosa). In the wild, is found in drier upland slopes and deep well drained soils in lowlands and valleys over most of eastern North America. I have observed magnificent trees in urban, suburban and natural areas. Have yet to be disappointed by performance. Estimate 60 to 80’ high. National Champion is 104’ by 99’. Zone 4 to 8 (9).

Carya laciniosa, shellbark hickory, differs from C. ovata in leaflet number, primarily 7, and the absence of tufts of pubescence (hairs) near the tips of serrations. Buds, bark, nuts (sweet seeds) are similar. Safe to state, I am never sure about positive identification between this and C. ovata until examining the leaves. Estimate 60 to 80’ in height; the National Champion 109’ by 112’. Found in bottomlands and floodplains, New York to Alabama to Missouri and Arkansas. Not as common as C. ovata. Zone 5 to 8.

Carya tomentosa, mockernut, white hickory, is a common species over most of eastern North America. The leaves and stems are covered with brown pubescence which persists and permits easy identification. The leaves are composed of 7 to 9 leaflets, the upper pair 5 to 9” long, 3 to 5” wide, the lower pair two-thirds that size. Leaves are dark yellow green, fragrant when bruised, and develop deep golden yellow to golden brown fall color.  Nuts are elliptical to rounded, 1 to 11/2” long, angled, with a ¼ to 1/3” husk splitting to the base. The seed is edible. Habit is narrow to broadly rounded. The bark develops interlacing ridges forming a diamond to netlike pattern. Common to dry habitats of uplands, including ridges and hillsides. To 3,000’ in the southern Appalachians. I estimate 50 to 60’ high under landscape conditions. Many trees in the Athens area supersede this size. The National Champion checks in at 140’ high and 85’ wide. Zone 4 to 9.

The other U.S. species are C. floridana, scrub hickory, C. myristiciformis, nutmeg hickory, C. pallida, pale or sand hickory, and C. texana, black hickory.

This mini treatise will hopefully inspire readers to become familiar with Carya, hickories. They are remarkable Noble trees that for too long have flown under the landscape radar. I believe the Chinese Proverb, “The best time to plant a tree was 20 years ago; the next best time is today”, applies to hickories. In my 78^th year, I planted a Carya aquatica grown from seed collected at the USDA Germplasm Repository in Beltsville, MD. The quote, “The true meaning of life is to plant trees under whose shade you do not expect to sit”, rings true for my effort.