Summary ³

Carya ovalis, the Red Hickory or Sweet Pignut Hickory, is a fairly uncommon but widespread hickory native to eastern North America. It is typically found growing in dry, well drained sandy upland ridges and sloped woodlands from southern Ontario, Canada, and in the United States east to New Hampshire, south to northern Florida west to eastern Texas and north-west to Nebraska. This species was formerly treated as a variety or northern ecotype of the Pignut Hickory...

Associated forest cover ⁴

Hickories are consistently present in the broad eastern upland  climax forest association commonly called oak-hickory, but they  are not generally abundant (18). Locally, hickories may make up  to 20 to 30 percent of stand basal area, particularly in slope  and cove forests below the escarpment of the Cumberland Plateau  (23) and in second-growth forests in the Cumberland Mountains,  especially on benches (14). It has been hypothesized that hickory  will replace chestnut (Castanea dentata) killed by the  blight (Cryphonectria parasitica) in the Appalachian  Highlands (10,12). On Beanfield Mountain in Giles County, VA, the  former chestnut-oak complex has changed to an oak-hickory  association over a period of 50 years. This association is  dominated by pignut hickory with an importance value of 41.0  (maximum value = 300), northern red oak (36.0), and chestnut oak  (25.0). White oak, red maple (Acer rubrum), and sugar  maple are subdominant species.

    Pignut hickory is an associated species in 20 of the 90 forest  cover types listed by the Society of American Foresters for the  eastern United States (6):

    Northern Forest Region

    53 White Pine-Chestnut Oak

    Central Forest Region

    40 Post Oak-Blackjack Oak
  44 Chestnut Oak
  45 Pitch Pine
  46 Eastern Redcedar
  52 White Oak-Black Oak-Northern Red Oak
  53 White Oak
  55 Northern Red Oak
  57 Yellow-Poplar
  59 Yellow-Poplar-White Oak-Northern Red Oak
  64 Sassafras-Persimmon
  110 Black Oak

    Southern Forest Region

    75 Shortleaf Pine
  76 Shortleaf Pine-Oak
  78 Virginia Pine-Oak
  79 Virginia Pine
  80 Loblolly Pine-Shortleaf Pine
  81 Loblolly Pine
  82 Loblolly Pine-Hardwood
  83 Longleaf Pine-Slash Pine

    Because the range of pignut hickory is so extensive, it is not  feasible to list the associated trees, shrubs, herbs, and  grasses, which vary according to elevation, topographic  conditions, edaphic features, and geographic locality.

Comments ⁵

Carya glabra is a highly polymorphic species. Tight-barked trees bearing large pear-shaped fruits are common along the Gulf Coast ( C . glabra var. megacarpa and C . leiodermis , C . magnifloridana ). Trees with exfoliating bark, reddish petioles, and small, compressed, ellipsoid fruits that dehisce to the base (i.e., C . ovalis ) are more common at higher latitudes. Carya glabra intergrades with C . floridana , C . pallida , and C . texana , and it is reported to hybridize with the diploid C . cordiformis ( C . × demareei Palmer). The extreme northern ovalis form of the species also appears to hybridize with the typical glabra in areas of sympatry.

Damaging agents ⁶

Pignut hickory is easily damaged by fire,  which causes stem degrade or loss of volume, or both. Internal  discolorations called mineral streak are common and are one major  reason why so few standing hickories meet trade specifications.  Streaks result from yellow-bellied sapsucker pecking, pin knots,  worm holes, and mechanical injuries. Hickories strongly resist  ice damage and seldom develop epicormic branches.

    The Index of Plant Diseases in the United States lists 133 fungi  and 10 other causes of diseases on Carya species (4,9).  Most of the fungi are saprophytes, but a few are damaging to  foliage, produce cankers, or cause trunk or root rots.

    The most common disease of pignut hickory from Pennsylvania  southward is a trunk rot caused by Poria spiculosa. Cankers  vary in size and appearance depending on their age. A common form  develops around a branch wound and resembles a swollen, nearly  healed wound. On large trees these may become prominent burl-like  bodies having several vertical or irregular folds in the callus  covering. A single trunk canker near the base is a sign that the  butt log is badly infected, and multiple cankers are evidence  that the entire tree may be a cull.

    Major leaf diseases are anthracnose (Gnomonia caryae) and  mildew (Microstroma juglandis). The former causes brown  spots with definite margins on the undersides of the leaf. These  may coalesce and cause widespread blotching. Mildew invades the  leaves and twigs and may form witches' brooms by stimulating bud  formation. Although locally prevalent, mildew offers no problem  in the management of hickory.

    The stem canker (Nectria galligena) produces depressed  areas with concentric bark rings that develop on the trunk and  branches. Affected trees are sometimes eliminated through  breakage or competition and sometimes live to reach merchantable  size with cull section at the canker. No special control measures  are required, but cankered trees should be harvested in stand  improvement operations.

    A gall-forming fungus species of Phomopsis can produce  warty excrescences ranging from small twig galls to very large  trunk burls on northern hickories and oaks. Little information is  available on root diseases of hickory.

    More than 100 insects have been reported to infest hickory trees  and wood products, but only a few cause death or severe damage  (1). The hickory bark beetle (Scolytus quadrispinosus) is  the most important insect enemy of hickory, and also one of the  most important insect pests of hardwoods in the Eastern United  States. During drought periods in the Southeast, outbreaks often  develop and large tracts of timber are killed. At other times,  damage may be confined to the killing of a single tree or to  portions of the tops of trees. The foliage of heavily infested  trees turns red within a few weeks after attack, and the trees  soon die. There is one generation per year in northern areas and  normally two broods per year in the South. Control consists of  felling infested trees and destroying the bark during winter  months or storing infested logs in ponds.

    Logs and dying trees of several hardwood species including pignut  hickory are attacked by the ambrosia beetle (Platypus  quadridentatus) throughout the South and north to West  Virginia and North Carolina. The false powderpost beetle (Xylobiops  basilaris) attacks recently felled or dying trees, logs, or  limbs with bark in the Eastern and

    Southern States. Hickory, persimmon (Diospyros virginiana),  and pecan (C. illinoensis) are most frequently  infested, but other hardwoods also are attacked. Healthy trees  growing in proximity to heavily infested trees are occasionally  attacked but almost always without success. Hickory and persimmon  wood (useful in the manufacture of small products such as shuttle  blocks, mallets, and mauls) is sometimes seriously damaged.

    Hickory is one of several host species of the twig girdler (Oncideres  cingulata). Infested trees and seedlings are not only damaged  severely but become ragged and unattractive. A few of the more  common species of gall-producing insects attacking hickory are  Phylloxera caryaecaulis, Caryomyia holotricha, C.  sanguinolenta, and C. tubicola.

Genetics ⁷

Carya glabra var. megacarpa (Sarg.) Sarg., coast  pignut hickory, was once recognized as a distinct variety but is  now considered to be a synonym of C. glabra (Mill.)  Sweet. C. leiodermis Sarg., swamp hickory, has also been  added as a synonym of C.glabra (11).

    Carya glabra (Mill.) Sweet var. glabra distinguishes  the (typical) pignut hickory from red hickory (C. glabra var.  odorata (Marsh.) Little). The taxonomic position of red  hickory is controversial. The binomial C. ovalis (Wangenh.)  Sarg. was published in 1913 for a segregate of C. glabra.  It was reduced to a synonym of C. glabra in Little's  1953 checklist but was elevated to a variety in the 1979 edition  (11). The principal difference is in the husk of the fruit,  opening late and only partly, or remaining closed in C.  glabra but promptly splitting to the base in C.ovalis.  However, many trees are intermediate in this trait, and the  recorded ranges are almost the same. The leaves of C. ovalis  have mostly seven leaflets; those of C. glabra have  mostly five leaflets. The two can be distinguished with certainty  only in November. Since the two ranges seem to overlap, the  distributions have been mapped together as a Carya  glabra-ovalis complex (11).

    Carya ovalis has also been treated as an interspecific  hybrid between C. glabra and C.ovata. C.  ovalis was accepted as a polymorphic species especially  variable in the size and shape of its nuts and possibly a hybrid.  The relationships may be more complex after a long and reticulate  phylogeny, according to detailed chemical analyses of hickory nut  oils.

    One hybrid, C. x demareei Palmer (C. glabra x  cordiformis) was described in 1937 from northeastern  Arkansas.

Importance to livestock and wildlife ⁸

More info for the term: mast

Browse: White-tailed deer occasionally browse pignut hickory, and small
mammals may eat the leaves [51].

Nuts: Pignut hickory nuts provide food for the fox squirrel in many
areas [33] and are preferred by the gray squirrel during fall and winter
in parts of New York [31]. Hickory nuts may comprise up to 10 to 25
percent of squirrel diets in some locations [51]. The eastern chipmunk
relies on hickory nuts for 5 to 10 percent of its diet [51]. Hickory
nuts are also eaten by the black bear, gray fox, raccoon, red squirrel,
pocket mouse, woodrat, and rabbits [27,51]. Hickory nuts are utilized
by black bears at lower elevations in parts of New England during the
fall; the abundance of such mast crops can affect black bear
reproductive success during the following year [12]. Value to fur and
game mammals is good [8].

Hickory nuts are eaten by many birds including the woodduck, ring-necked
pheasant, northern bobwhite, wild turkey, common crow, bluejay,
white-breasted nuthatch, red-bellied woodpecker, and yellow-bellied
sapsucker [37]. The value of hickory nuts to upland game birds and
songbirds is fair [8].

Key plant community associations ⁹

More info for the term: hardwood

Pignut hickory codominates certain upland hardwood forests of eastern
North America. Common codominants include white oak (Quercus alba) and
northern red oak (Q. rubra). Pignut hickory is included as a dominant
or indicator in the following community type classifications (cts):

Area Classification Authority

sw OH forest cts Braun 1936
TN general veg. cts Quarterman and others 1972

Nutritional value ¹⁰

Browse: The nutrient content of pignut hickory browse varies
seasonally. Mean foliar ash content has been reported as 12.75 percent
in the spring and 11.61 percent during the fall [28].

Nuts: Pignut hickory nuts are high in protein and fats [31]. Crude fat
content may reach 70 to 80 percent in some species of hickory [51].
Nuts are moderate to low in phosphorus, and calcium and very low in
crude fiber [51]. The nuts provide a relatively low rate of energy
uptake for gray squirrels.

Sources and Credits

1. (c) Jennifer Reed, some rights reserved (CC BY-NC), uploaded by Jennifer Reed
2. (c) "<a href=""http://www.nal.usda.gov/"">National Agricultural Library</a>. Originally from <a href=""http://www.fs.fed.us/"">US Forest Service</a>. United States, DC, Washington.", some rights reserved (CC BY-NC-SA), https://plants.usda.gov/gallery/large/cagl8_007_lvp.jpg
3. Adapted by Jonathan (JC) Carpenter from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Carya_ovalis
4. (c) Unknown, some rights reserved (CC BY-NC), http://eol.org/data_objects/22778193
5. (c) Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/19823107
6. (c) Unknown, some rights reserved (CC BY-NC), http://eol.org/data_objects/22778201
7. (c) Unknown, some rights reserved (CC BY-NC), http://eol.org/data_objects/22778202
8. Public Domain, http://eol.org/data_objects/24640908
9. Public Domain, http://eol.org/data_objects/24640907
10. Public Domain, http://eol.org/data_objects/23370119

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