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.
Gossard(9) reported success in producing roots from the tops of small grafted and budded pecan trees by trench layering and from older trees by aerial layering with marcot boxes. He indicated that a favorable combination of etiolation, moisture, rooting medium, and a root-inducing chemical was desirable for successful rooting.
Propagation by Cuttings
Hardwood cuttings of pecan were rooted by Stoutemyer and O'Rourke(23) in 1938 by first callusing the bases of the cuttings in warm moist peat moss, and then treating with an aqueous solution of indole butyric acid before planting. Both roots and shoots grew well for three to four weeks and then the shoots wilted and died. It was observed that the roots were thickened and presented an abnormal appearance. Trials during succeeding years gave no better results and the experiments were discontinued. Cuttings taken from native hickories during these same years failed to produce roots.
Romberg(17) reported a small measure of success in rooting hardwood stem cuttings to which young seedlings had been grafted by the inarch method. The influence of the seedling on the nourishment of the cutting was gradually diminished by girdling caused by a copper wire which was tied about the seedling stem.
Apparently root cuttings of pecans and other hickories have never been tried. In 1896 Corsa(7) observed that "when the lateral roots of the pecan are broken by the plow, the ends of these roots frequently send up thrifty shoots." Such a response would indicate that adventitious shoots may arise from roots and that root cuttings may be successful.
Propagation by Grafting
A search of the literature failed to reveal a discussion of any method of bench grafting with hickories, although presumably it must have been tried. Propagators may have been discouraged in using bench graft methods by the sparse roots usually found on two-year seedlings. It is suggested that undercutting and root pruning the seedlings several times while in the nursery row should produce a more adequate root system which would transplant well after grafting. Brison(5) remarked that bench grafting is not used in the propagation of pecans in Texas on account of transplanting difficulties.