Sexual Propagation (by seed)
Propagation by seed is typically only used to produce seedling rootstocks for grafting cultivar clones. Collect well-filled nuts during harvest season to produce a seedling. Remove husks and dry nuts to about 5% moisture. Pecan nuts have a protective shell which delays germination. To break dormancy, stratify nuts between 36° and 41°F for at 30 to 90 days before moving them to room temperature. Allow seeds to acclimate to ambient room temperature at least one week before planting. Seeds can also be soaked in water the day before planting, causing the suture to split and breaking dormancy. Seeds should be planted in late winter, before March 1st. After two years a seedling should be 4-5 feet tall and ready for grafting (McEachern, 2000; Peterson, 1990).
Vegetative Propagation (grafting & budding)
Pecan trees are usually grafted in the spring of the third growing season or patch budded in late summer of the second growing season.
Scion wood should be collected during the dormant period (between January and March) from straight one year old shoots 1/4 to 5/8 inch in diameter. Scion wood should be used immediately to prevent bud damage due to drying out, freezing, insect damage or disease. If the scion must be stored, it should be packed in moist wood shavings in a plastic bag to prevent drying out, and placed between 30° and 38° F (Wells, 2010).
Whip Graft
A whip graft requires a scion with 3 to 4 buds and seedling rootstock approximately the same diameter. Two year old dormant seedlings are typically whip grafted in February and March. Make a slanted cut of the same length on both the rootstock and the scion; then place them together so the cambium layers align and wrap with parafilm, grafting tape, or a rubber band to hold the graft in place (Wells, 2010). If successful, the scion will produce new shoots in 4 to 6 weeks (McEachern, 2000). Grafted trees typically bear fruit in the 4th leaf after grafting.
Four flap or “banana” graft
The four flap or banana graft is the easiest graft to perform with a high success rate because it allows more cambium contact than other grafts. The scion and rootstock should be similar in diameter, with the scion slightly larger than the rootstock. Scion wood, one-year old shoots collected in the dormant season, should be 3/8 to 1 inch diameter. Each scion should be about 6 inches long, and have two to three buds.
Four flap grafts should be made in early spring when rootstock bark begins to slip. Make a flat cut through the bark, exposing the cambium layer, on all sides of the scion. The cuts should be one to two inches from the bottom end, tapering at the bottom end, so a square forms at the base of the scion wood where it will fit into the rootstock.
Make four cuts about 2 to 2 ½ inches from the top of the rootstock and pull down the four flaps of bark to expose the bare wood. Carefully cut the exposed rootstock, without damaging the flaps. Insert the tapered end of the scion and pull up the four flaps to cover the exposed cambium. Secure the four flaps of scion wood with grafting tape, rubber band, or parafilm. The graft should start to grow in three to four weeks (Wells, 2010).
Patch Bud
Collect current season budsticks (scion wood) with mature buds. Scion bark with a white underside is mature. Handle budwood with great care and remove (clip) all leaves from the bud stick. If buds are collected from stored scion wood, the scion should be placed in room temperature at about 80°F, four to six days before using. Patch budding can be done on rootstocks at least 3/8 inch in diameter when bark is slipping, typically in July or August. A double bladed knife is used to make equal size square cuts on both scion and rootstock. Patches must fit precisely for a successful graft. After the bud from the scion has been cut and patched onto the rootstock, securely wrap the bud patch with grafting tape, rubber band or parafilm. Cover the entire patch except for the bud itself. If the bud graft is successful, cut off the rootstock about 3 inches above the patch bud after growth begins (Wells, 2010).