Hickories
Carya cordiformis
C. cordiformis (Wangenh.) K. Koch. Bitternut Hickory
Bitternut hickory is possibly
the most widely and uniformly distributed hickory, being found
as far north as southern Quebec, Canada and as far south as the
Gulf Coast of Louisiana. It is found throughout the Eastern United
States from New Hampshire south to Florida and west to Minnesota
and eastern Texas (distribution
map) . The species
occurs on a wide range of sites, from dry upland sites in the
southwestern part of its range to low wet woods in Louisiana (Fowells
1965, Grauke et al 1987). Bitternut is a major component of the
White Oak-Red Oak-Hickory forest in the northern U.S. and of the
Swamp Chestnut Oak-Cherrybark Oak forest in the south (Fowells
1965).
C. cordiformis is easily recognized by its distinctive buds, leaves, nuts and bark. Terminal buds have sulphur yellow,
leaf-like bud scales. Leaves are distinctive by the combination
of their general symmetry and the presence of large, clear, plate-like
scales on the lower leaflet surface, near the basal margin of
the leaflet. The fruit is a slightly flattened sphere with a prominent
point at the apex, making the nut almost heart-shaped. The name
"cordiformis" means "heart-shaped". Husks
are thin and have prominent wings on the sutures from the apex
to the middle of the nut. Husks dehisce to the middle, but the
nut often drops in the husk. Nuts have very thin shells marked
by shallow grooves. Cross sections of the nuts reveal prominent
lacunae and a well developed secondary septum which extends to
the middle of the nut. Kernels are crinkled and bitter. The bark
of mature trees is tight, smooth and very light gray, a feature
shared by the Mexican endemic C. palmeri.
The wood of C. cordiformis is inferior to that of the true hickories,
leading Boisen and Newlin (1910) to recommend that it not only
should not be planted, but should be removed from existing stands
in favor of shagbark, shellbark, pignut and mockernut.
C. cordiformis has received little horticultural attention, due
to its bitter kernel. There are however, two named cultivars of
bitternut, 'Halesite' and 'Hatch'. Willard Bixby entered the nuts of
'Halesite' in the Northern Nut Grower's 1918 nut contest and won
the title of "thinnest shelled hickory". The 'Dennis' hickory is also C. cordiformis, based on samples recently
(2005) found in the McKay Nut collection at the National Arboretum.
When shell thickness was compared on 10 nuts from each of 5 trees
from each of the 13 U.S. hickories, the thinnest shells were found
on C. aquatica, while bitternut and pecan could not be distinguished
(Ring, unpublished data).
Interspecific hybrids have been reported between C. cordiformis
and pecan (C. X brownii). McDaniel (1968) speculated that interspecific
hybridization between pecan and bitternut might have extended
the northern range of pecan by contributing genes for early ripening
of nuts. Named cultivars of that cross include 'Galloway', 'Mall',
'Nelson', 'Pleas', 'Pooshee', and 'Westbrook'(see Table 3). Hybrids
typically have nuts which are somewhat flattened, have prominent
apices, and are four-celled at the base due to the presence of
a secondary septum as in C. cordiformis. Nuts may be astringent,
as in 'Pleas', or "sweet-fruited" as in 'Galloway' (see
Trelease 1896).
Interspecific hybrids have also been reported between C. cordiformis
and C. ovata (C. X laneyi). Detailed description of this family
of crosses is offered by Manning (1948). The following cultivars
have been named; 'Beaver', 'Creager', 'De Acer', 'Fairbanks',
'Laney' (type tree), 'Peck', 'Roof', 'Stocking', 'Stratford',
'Terpenny', and 'Weschcke'. 'Brackett', wrongly attributed as a species of
Carya glabra, is also C. X laneyi (see Thompson and Grauke, 1991,
page 877). Samples of 'Brackett' were also found in the McKay
Nut Collection (LJG, 2005).
C. X demareei is supposedly a hybrid between C. cordiformis and
C. ovalis (see Palmer 1937). This hybrid is reported from the
area near Crowley's Ridge in northeastern Arkansas.
LJ Grauke
, Research Horticulturist
& Curator
USDA-ARS Pecan Genetics
10200 FM 50
Somerville, TX 77879
tele: 979-272-1402
fax: 979-272-1401
e-mail: ljg@tamu.edu
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