Hickories
Economic botany
In addition to being grown
for their nutritious and delicious nuts, hickories are also valued
for the utility and beauty of their wood, for their ornamental
value in the landscape, and for their quality as a fuel wood.
The wood of hickories is known for strength and shock resistance,
making it excellent for tool handles. It is also used extensively
for sports equipment such as golf clubs, baseball bats, the backs
of longbows, and laminae in tennis racquets and skis (Makepeace
and Walker, 1989). High quality hickory is used as a flooring
material for gymnasiums, roller skate rinks, and ballrooms. Some
wood is used in making furniture, in piano construction, for butcher's
blocks, for wall paneling, and interior trim. Hickory wood is
also used for dowels, ladder rungs, and pallets (Harrar, 1958).
Harrar (1958) reported that quality hickory lumber is in short
supply, with much of the standing timber being so defective that
harvest was not economical.
Hickory is considered to be an excellent fuel wood because of
its density. One pound of any hardwood species yields about the
same amount of heat as a pound of any other species of hardwood
(8,580 to 8,920 BTUs per pound). However, wood is sold by the
cord, which is a volume measure. Hickory wood is very dense, weighing
about 4600 lbs. per cord and producing about 25 million BTUs per
cord when burned. Lighter wood such as elm may weigh only 3200
lbs. per cord and produce 18 million BTUs when burned (Michaelson,
1978). Hickory wood is consumed in the smoking of meats and cheeses,
where it imparts a distinctive flavor.
Of the 13 species described above, only pecan, shagbark and shellbark,
have received much horticultural attention. In addition to their
intrinsic ecological value, the remaining species are potentially
useful for wood production or as specimen plants in the landscape.
As more information is gained concerning mechanisms of disease
and insect resistance or other genetic adaptations, these species
could contribute to the development of the closely related pecan.
Bringhurst (1983) outlined 4 steps usually followed in the development
of improved fruit crops from wild species: 1) identification of
superior phenotypes in natural populations; 2) propagation of
the best selections in an agricultural setting; 3) development
of cultural practices that enhance performance of selected cultivars;
and 4) hybridization among the best selections followed by selection
of superior offspring (which are used as parents for further crosses).
Despite their long history of utilization, the hickories are
still at an early stage of crop development. Many "superior
phenotypes" have been found in native populations, with nut
characteristics being the primary basis of evaluation. The characteristics
and performance of these "cultivars" following asexual
propagation has been the focus of much of the literature related
to hickory management. Unfortunately, observations are often
based on one stion of a cultivar, often with a rootstock of another
species and growing on mediocre sites.
A significant stage in the horticultural development of pecan
occurred when orchards were planted using selected seed. Seedlings
were evaluated for horticultural traits, with cultivars such as
'Stuart', 'Schley', 'Success', 'Delmas', 'Alley', and 'Pabst'
arising from "select seed orchards" in Jackson Co.,
Mississippi. 'Western', 'San Saba Improved', 'Sovereign' ('Texas
Prolific'), 'Onliwon', and 'Squirrels Delight' originated from
an orchard of 1000 trees grown from seed of the 'San Saba', a
native selection made by E. E. Risien of San Saba Co., Texas.
The James orchard at Mound, Louisiana, was planted from selected
seed and produced 'Carman', 'James', and 'Moneymaker' while in
Florida, 'Curtis', 'Hume', 'Kennedy', and 'Randall' arose from
the seedling orchard of J. B. Curtis (Crane et al., 1937).
Pecan cultivars have traditionally been selected primarily on
the basis of nut characteristics, with selections being asexually
propagated on seedling rootstocks in orchard configurations where
intensive management can be economically justified. The limitations
to economically feasible orchard establishment in the hickories
are the extremely long period of juvenility (> 10 years), low
yields (22 to 45 kg/tree, once in 3 yr), and large tree size.
These native trees are plagued by many co-evolved disease and
insect pests (Harris et al., 1986), especially when grown in a
"monoculture" having large numbers of a limited number
of cultivars. Conventional systems of orchard production have
emphasized chemical control of pests, which is both economically
and environmentally expensive. As a result, the culture of hickories
tends to be "unconventional", with most practitioners
being motivated more by aesthetics than economics.
The value of hickory wood creates an economic incentive to harvest
this slowly renewable forest resource. Wise management should
integrate the needs of forestry with a long range program of selection
for the improvement of the stand. The systematic maintenance,
management, and development of this valuable natural resource
deserves thoughtful attention.
Warren Chatwin , Research Geneticist
USDA-ARS Pecan Genetics
10200 FM 50
Somerville, TX 77879
tele: 979-272-1402
fax: 979-272-1401
e-mail: warren.chatwin@usda.gov
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