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...
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.
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.
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.
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.
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].
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
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.