Propagation of the Hickories[1]
F. L. O'ROURKE, Department of Horticulture, Michigan State College
The genus Carya comprises all the hickories and pecans found in the United States. The eighth edition of Gray's Manual of Botany lists the following species as being native to the United States:
[1] The survey of literature pertaining to this review was completed in August, 1952.
Carya aquatica—Water hickory, Bitter Pecan Carya cordiformis—Bitternut, Swamp Hickory Carya glabra—Pignut Carya illinoensis—Pecan Carya laciniosa—Shellbark, Kingnut Carya ovalis—Sweet Pignut, False Shagbark, Red Hickory Carya ovata—Shagbark Carya pallida—Pale Hickory Carya texana—Black Hickory Carya tormentosa (C. alba)—Mockernut
Nut growers are interested primarily in the pecan and the shagbark, although a few selections have been made of the shellbark species. The bitternut is quite often used for rootstocks for the shagbark and shagbark hybrids.
Hickories, like other nut and tree species, do not come true from seed, so superior selected clones are propagated by budding and grafting on other trees known as rootstocks. These rootstocks are produced from seed.
Seed Propagation
Investigations by Barton(1) showed that some seedlings were produced when the nuts were planted immediately in a warm greenhouse without pretreatment, but that germination was markedly increased when the nuts were held in a cool moist environment from one to four months before bringing into the greenhouse. She also found that fall planting of hickory nuts resulted in a good stand of seedlings the following spring if the soil was mulched, but that the freezing and thawing of unprotected ground resulted in an exceedingly poor stand of seedlings.
Burkett(6) advocated stratifying pecan seed over winter in moist sand and planting in moist soil in the very early spring. He observed that thin-shelled nuts germinate more quickly than thick-shelled ones, and warned against "damping-off" fungi which often killed young seedlings.