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. Brison(5) stated that some nurserymen prefer seed of certain pecan varieties as Riverside and Burkett for rootstock purposes as these produce strong vigorous seedlings. He reported that while the pecan seed does not have a rest period, germination is increased by stratifying in moist sand for 2 to 3 weeks or soaking in water, changed daily, for 4 to 5 days previous to planting. Propagation by Layering No records are available in regard to any hickory species or variety other than pecan having been propagated by any method of either soil or air layering. The writer(14) while experimenting with aerial layering in 1945 found one instance of root production on a hickory where the branch was girdled at the base of the one-year wood. This method offers possibilities, especially now that polythene plastic is available for retaining moisture in the moss about the girdle or wound on the layered branch.