Carya tomentosa, commonly known as mockernut hickory, mockernut, white hickory, whiteheart hickory, hognut, bullnut, is a species of tree in the walnut family Juglandaceae. The most abundant of the hickories, and common in the eastern half of the United States, it is long lived, sometimes reaching the age of 500 years. A straight-growing hickory, a high percentage of its wood is used for products where strength, hardness, and flexibility are needed. The wood makes excellent fuel wood, as well.
Description
Reproduction and early growth
Flowering and fruiting Mockernut hickory is monoecious - male and female flowers are produced on the same tree. Mockernut male flowers are catkins about long and may be produced on branches from axils of leaves of the previous season or from the inner scales of the terminal buds at the base of the current growth. The female flowers appear in short spikes on peduncles terminating in shoots of the current year. Flowers bloom in the spring from April to May, depending on latitude and weather. Usually the male flowers emerge before the female flowers. Hickories produce very large amounts of pollen that is dispersed by the wind.
Fruits are solitary or paired and globose, ripening in September and October, and are about long with a short necklike base. The fruit has a thick, four-ribbed husk thick that usually splits from the middle to the base. The nut is distinctly four-angled with a reddish-brown, very hard shell thick containing a small edible kernel.
Seed production and dissemination
The seed is dispersed from September through December. Mockernut hickory requires a minimum of 25 years to reach commercial seed-bearing age. Optimum seed production occurs from 40 to 125 years, and the maximum age listed for commercial seed production is 200 years.
Good seed crops occur every two to three years with light seed crops in intervening years. Around 50 to 75% of fresh seed will germinate. Fourteen mockernut hickory trees in southeastern Ohio produced an average annual crop of 6,285 nuts for 6 years; about 39% were sound, 48% aborted, and 13% had insect damage. Hickory shuckworm (Laspeyresia caryana) is probably a major factor in reducing germination.
Mockernut hickory produces one of the heaviest seeds of the hickory species; cleaned seeds range from 70 to 250 seeds/kg (32 to 113/lb). Seed is disseminated mainly by gravity and wildlife, particularly squirrels. Birds also help disperse seed. Wildlife such as squirrels and chipmunks often bury the seed at some distance from the seed-bearing tree.
Seedling development Hickory seeds show embryo dormancy that can be overcome by stratification in a moist medium at for 30 to 150 days. When stored for a year or more, seed may require stratification for only 30 to 60 days. Hickory nuts seldom remain viable in the ground for more than one year. Hickory species normally require a moderately moist seedbed for satisfactory seed germination, and mockernut hickory seems to reproduce best in moist duff. Germination is hypogeal.
Mockernut seedlings are not fast-growing. The height growth of mockernut seedlings observed in the Ohio Valley in the open or under light shade on red clay soil was:
Age Height (yr) (cm) (in) 1 8 3.0 2 12 4.7 3 20 8.0 4 32 12.5 5 51 20.0 6 71 28.0
Vegetative reproduction True hickories sprout prolifically from stumps after cutting and fire. As the stumps increase in size, the number of stumps that produce sprouts decreases; age is probably directly correlated to stump size and sprouting. Coppice management is a possibility with true hickories. True hickories are difficult to reproduce from cuttings. Madden discussed the techniques for selecting, packing, and storing hickory propagation wood. Reed indicated that the most tested hickory species for root stock for pecan hickory grafts were mockernut and water hickory (Carya aquatica).
However, mockernut root stock grew slowly and reduced the growth of pecan tops. Also, this graft seldom produced a tree that bore well or yielded large nuts.
Sapling and pole stages to maturity
Growth and yield Mockernut hickory is a large, true hickory with a dense crown. This species occasionally grows to about tall and in diameter at breast height (dbh), but heights and diameters usually range from about , respectively.
The relation of height to age is:
Height Age Cumberland Mountains Mississippi Valley (yr) (m) (ft) (m) (ft) 10 1.2 4 2.7 9 20 5.2 17 5.5 18 30 7.9 26 7.6 25 40 10.1 33 9.1 30 60 13.7 45 12.2 40 80 16.8 55 14.9 49 100 20.1 66 17.4 57 120 23.2 76 19.8 65 160 28.7 94 24.4 80 200 33.2 109 29.0 95
The current annual growth of mockernut hickory on dry sites is estimated at 1.0 m3/ha (15 ft3/acre). In fully stocked stands on moderately fertile soil2.1 m3 /ha (30 ft3 /acre) is estimated, though annual growth rates of 3.1 m3/ha (44 ft3/acre) were reported in Ohio (26). Greenwood and bark weights for commercial-size mockernut trees from mixed hardwoods in Georgia are available for total tree and saw-log stems to a 4-inch top for trees 5 to 22 inches d.b.h..
Available growth data and other research information are summarized for hickory species, not for individual species. Trimble compared growth rates of various Appalachian hardwoods including a hickory species category dominant-codominant hickory trees in dbh on good oak sites grew slowly compared to northern red oak, yellow-poplar, black cherry (Prunus serotina), and sugar maple (Acer saccharum). Hickories were in the white oak, sweet birch (Betula lenta), and American beech (Fagus grandifolia) growth-rate category. Dominant-codominant hickory trees grew about dbh per year compared to for the moderate-growth species (black cherry) and for the faster-growing species (yellow-poplar and red oak). Equations are available for predicting merchantable gross volumes from hickory stump diameters in Ohio. Also, procedures are described for predicting diameters and heights and for developing volume tables to any merchantable top diameter for hickory species in southern Illinois and West Virginia. Generally, epicormic branching is not a problem with hickory species, but a few branches do occur.
The leaves turn yellow in Autumn.
Rooting habit True hickories such as mockernut develop a long taproot with few laterals. Early root growth is primarily into the taproot, which typically reaches a depth of during the first year. Small laterals originate along the taproot, but many die back during the fall. During the second year, the taproot may reach a depth of , and the laterals grow rapidly. After 5 years, the root system attains its maximum depth, and the horizontal spread of the roots is about double that of the crown. By age 10, the height is four times the depth of the taproot.
Etymology The species' name comes from the Latin word tomentum, meaning "stuffing", referring to the underside of the leaves, which are covered with dense, short hairs, which help identify the species. Also called the white hickory due to the light color of the wood, the common name mockernut likely refers to the would-be nut eater, who would struggle to crack the thick shell only to find a small, unrewarding nut inside.
Distribution and habitat
Native range Mockernut hickory, a true hickory, grows from Massachusetts and New York west to southern Ontario, and northern Illinois; then to southeastern Iowa, Missouri, and eastern Kansas, south to eastern Texas and east to northern Florida. This species is not present in Michigan, New Hampshire and Vermont as previously mapped by Little.Manning, W. E. 1973. The northern limits of the distributions of hickories in New England. Rhodora 75(801):34-35. Mockernut hickory is most abundant southward through Virginia, North Carolina, and Florida, where it is the most common of the hickories. It is also abundant in the lower Mississippi Valley and grows largest in the lower Ohio River Basin and in Missouri and Arkansas.Nelson, Thomas C. 1959. Silvical characteristics of mockernut hickory. USDA Forest Service, Station Paper 105. Southeastern Forest Experiment Station, Asheville, NC. 10 p.Nelson, Thomas C. 1965. Silvical characteristics of the commercial hickories. USDA Forest Service, Hickory Task Force Report 10. Southeastern Forest Experiment Station, Asheville, NC. 16 p.
Climate The climate where mockernut hickory grows is usually humid. Within its range, the mean annual precipitation measures from in the north to in the south. During the growing season (April through September), annual precipitation varies from . About of annual snowfall is common in the northern part of the range, but snow is rare in the southern portion.
Annual temperatures range from . Monthly average temperatures range from in July and from in January. Temperature extremes are well above and below . The growing season is about 160 days in the northern part of the range and up to 320 days in the southern part of the range.U.S. Department of Agriculture. 1941. Climate and man. U.S. Department of Agriculture, Yearbook of Agriculture. Washington, DC. 1248 p.U.S. Department of Commerce, Environmental Science Service Administration. 1968. Climatic atlas of the United States. U.S. Department of Commerce, Environmental Data Service, Washington, DC. 80 p.
Soils and topography In the north, mockernut hickory is found on drier soils of ridges and hillsides and less frequently on moist woodlands and alluvial bottoms. The species grows and develops best on deep, fertile soils.Halls, Lowell K., ed. 1977. Mockernut history, Carya tomentosa. In Southern fruit producing woody plants used by wildlife. p. 142-143. USDA Forest Service, General Technical Report SO-16. Southern Forest Experiment Station, New Orleans, LA. In the Cumberland Mountains and hills of southern Indiana, it grows on dry sites such as south and west slopes or dry ridges. In Alabama and Mississippi, it grows on sandy soils with shortleaf pine (Pinus echinata) and loblolly pine (P taeda). However, most of the merchantable mockernut grows on moderately fertile upland soils.
Mockernut hickory grows primarily on ultisols occurring on an estimated 65% of its range, including much of the southern to northeastern United States.U.S. Department of Agriculture, Soil Conservation Service 1975. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. U.S. Department of Agriculture, Agriculture Handbook 436. Washington, DC 754 p. These soils are low in nutrients and usually moist, but during the warm season, they are dry part of the time. Along the mid-Atlantic and in the southern and western range, mockernut hickory grows on a variety of soils on slopes of 25% or less, including combinations of fine to coarse loams, clays, and well-drained quartz sands. On slopes steeper than 25%, mockernut often grows on coarse loams.
Mockernut grows on inceptisols in an estimated 15% of its range. These clayey soils are moderate to high in nutrients and are primarily in the Appalachians on gentle to moderate slopes, where water is available to plants during the growing season. In the northern Appalachians on slopes of 25% or less, mockernut hickory grows on poorly drained loams with a fragipan. In the central and southern Appalachians on slopes 25% or less, mockernut hickory grows on fine loams. On steeper slopes, it grows on coarse loams.
In the northwestern part of the range, mockernut grows on mollisols. These soils have a deep, fertile surface horizon greater than thick. Mollisols characteristically form under grass in climates with moderate to high seasonal precipitation.