Hybrid Hickory Variety Recommendations and Propagation Trials

Commodities

• Nuts: Hickories

Practices

• Crop Production: agroforestry

This is a research project with two main barriers, both of which
will be important to break in order to make hickories a crop in
the upper midwest.

1. Tree evaluations need to be done on hundreds of hybrid
   individuals in the upper midwest to provide variety
   recommendations for growers in the upper Midwest. Currently, only
   a small handful of subpar hickory selections have been made and
   often have been trialed only outside of zone 4/5 upper midwest.
   Additionally, evaluations are almost entirely anecdotal and
   insufficient to give growers security in planting varieties that
   are of high cost and may take over a decade to bear nuts.
2. A procedure for epicotyl grafting hickories (grafting onto a
   sprouted nut) in zone 4/5 needs to be developed. Traditional
   nursery growing of hickories is challenging and problematic due
   to the high costs of producing grafted trees because of slow
   seedling shoot growth, strong taproot dominance, and the stress
   responses of hickories.

The first objective is to select 10 hybrid hickory varieties to
be recommended to growers in zone 4/5 upper midwest that will
provide maximum profitability and flexibility to the grower and
release them for sale. I will select hickory trees that are easy
to propagate, fast growing, disease resistant, heavy bearing,
easy to harvest and husk, and bears multipurpose nuts. A
multipurpose nut that grows in zone 4/5 upper midwest can only be
found in some bitternut shagbark hybrids. A multipurpose nut is
one that can be used for multiple of the following purposes:
home-scale cracking, machine cracking, oil pressing, and milking.
The characteristics that allow for a combination of these four
puroses are:

• the kernel weight should be as large as possible with 2.0g as
  a minimum
• the nut should have a thin enough shell that it can be
  pressed in-shell for oil reliably. Current knowledge estimates
  that the nut should be at or exceed 47% kernel.
• the nut should crack out exceedingly well in a home scale
  hand cracker with at least 50% of kernel to halves and 90% easy
  extraction to large pieces
• the nut should be milkable which requires that the kernel,
  pellicle, and shell not to contain tannins.
• The nut shape should lend itself to automated machine
  crackering.

The second objective of this project is to determine the details
in the procedure of epicotyl grafting hickories to get maximal
grafting success. Though I have successfully epicotyl grafted
with Black Walnut and the method has been successful with pecan,
epicotyl grafting has not been applied to bitternuts, shagbarks,
or their hybrids. Many specifics of the epicotyl grafting process
with hickories needs to be discovered including: the best hybrid
rootstock, the best shoot development stage for high graft
success and rapid growth, the best waxing and compression method,
and the lowest input nursery growing conditions that work with
the Wisconsin climate.

For the epicotyl grafting trials, three rootstocks will be
tested: "Fairbanks", "Weschcke", and a 3.0g kernel shagbark. Past
trials show that pure shagbark and "Weschcke" produce the
thickest diameter epicotyl which is easier to handle. 100%
beeswax will be used that has no oil in the mix because the oil
seems to have killed callus in past trials. Suxgumoe Plants Graft Clips will be used as
determined by my past trials and sizing. Three compression
and wrapping methods will be used: parafilm wrapping, parafilm
wrapping and clipping, and only clipping. All grafts will be
waxed to the bottom of the graft union. Nuts will be placed in a
germ chamber for 20 to 25 days at 90F and epicotyls of length
varying from 1 inch to 6 inches will be grafted, segregated, and
labeled with all characteristics of relevance to this study.
Grafts will be callused in a greenhouse heated to 70F, fans will
run above 85F, and sides will be rolled up to help keep temps
within this range. After 5 weeks, 75% of grafts will be planted
into a rodent proof nursery bed for two years and 25% will be
planted into 9" tall 4" wide tree pots. Winter survival rates
will be noted for field planted grafts. Nut germination will be
initiated on ~March 25th, grafting will occur on ~April 20th, and
transplanting will occur on ~May 25th. A minimum of 300 grafts
will be made.