By Dr. George Ray McEachern
Professor and Extension Horticulturist
January 17, 2000
There is something special about grafting. To make a new tree of the very best variety has been a major part of pecan production since Antoine grafted the first variety, Centennial, at Oak Alley Plantation on the west bank of the Mississippi River just north of New Orleans in 1846.
Magic, thrill, suspense, gratification, and sadness always go hand-in-hand when pecans are grafted. In the old days, according to Harold Hume of North Carolina (in 1906) and Stuckey and Kyle of Georgia and Texas (in 1925), the pecan is difficult to propagate. The old-time grafters did not want others to learn the tricks of grafting, so they would go high in the tree to be out of sight. However, by the time of Brison in 1974, propagating pecans was not difficult, because several systems had been fine-tuned, and survival percentage was very high, even in arid climates such as West Texas. In the year 2000, we take grafting pecans for granted, because it is easy. However, if special attention is not paid to details, propagating pecans can be difficult or impossible.
To propagate pecan trees, grafting or budding is needed, because the seed is not true to type. If one plants a seed, the tree that develops will be different from the tree from which the seed was harvested. All native and seedling trees are different from each other, with no two being the same. Attempts by Nigel Wolstenhome and others to propagate pecans by cuttings or layerage failed to become commercially acceptable. The pecan is different from most plants because its cuttings do not produce roots, and thus grafting is needed to propagate many trees of one variety.
Collect well-filled seed nuts in October or November, and dry to about 5 percent moisture, or until the kernel snaps when bent. Store the seed nuts in refrigeration at about 45 degrees F. in poly bags, with or without slightly moist packing material. Do not let the temperature drop below 32 degrees F. One week before planting, remove the seed from refrigeration and warm to room temperature. One day before planting, soak the seed in running water. After at least 24 hours, remove nuts, which have swelled, showing a split in the suture. Some may need longer soaking to split. Plant the seed sideways 3 to 4 inches deep in either a nursery row, a raised bed, or a 55-gallon barrel with both ends cut out. After one year, the seedlings should be 6 to 18 inches tall.
In the humid southeast -- from Savannah, Georgia to Tyler, Texas -- one-year pecan seedlings growing in the nursery row can be whip-grafted dormant in January or February, wrapped with wax tape, and covered with soil. The graft can grow 2 to 8 feet in one growing season. The trees can be dug by hand, or with a U-blade, pushed or pulled by a bulldozer, or scooped out with a giant backhoe. These digging systems can be used for all nursery trees less than 10 feet tall.
In Texas [west of Tyler] and New Mexico, the climate is too dry for whip-grafting, so the patch bud is used in July and August at the end of the second year of seedling growth. The graft will grow the third year, producing a tree with a three-year-old root and one-year-old graft. The patch bud can also be used for top-working mature trees, but it is seldom used because it requires too much after-care. Once the variety scion-shoot begins to grow, it needs to be tied to a stake. Some nurserymen strip the bark off the rootstock, and tie the scion shoot to the stripped rootstock.
Commercial nurserymen use the patch bud to graft in the spring, using dormant graftwood sticks which are collected very late in the dormant season. Spring patch-budding can be difficult and frustrating, because the buds will not slip and pop off of the graftwood stick. Dormant graftwood to be used for spring patch-budding needs to be collected late enough for sap flow but before the earliest signs of bud-break, or before the outer bud scale of the primary buds begins to swell and split.
Small trees with a diameter less than one inch can be grafted with the four-flap graft in April or May when the bark slips easily. This graft, which is also call the banana graft, was developed in Tennessee but became popular in Oklahoma, and is now used in Texas for small trees. Debs Grantham of Rosharon, Texas developed a special tool which makes the four-flap graft easier to cut. Austin Stockton added a rubber band to the technique, which made it very easy to use, with a very high percentage of takes. Small trees or limbs up to 2 inches in diameter can be grafted when the bark slips, using the Texas-method inlay-bark graft. This graft was developed by L. D. Romberg and Fred Brison; however, Bluefford Hancock is recognized for introducing the graft to all pecan-growing areas of Texas through Extension field-days for over 30 years. More people know how to graft in Texas than in any other state in the country because of the widespread success of the inlay-bark graft with pecans. This is the most successful graft used in an arid climate. Top-worked grafts on mature trees can begin to bear in the third year.
For the whipgraft, dormant graftwood sticks (the diameter of the seedlings to be grafted) are collected the same day in January or February. Since the sticks are used immediately, no special attention is given to packing or storing. Patch-bud graft sticks are collected in July or August from current-season shoots (with the leaves attached) the same day they are used. The sticks need to be the same size of the seedling trees being grafted; store sticks, wrapped in slightly damp paper, in an ice chest. The grafts do not store well, so collect them daily.
Graftwood for the four-flap graft and the inlay-bark graft should be collected in late January or early February when the wood is most dormant. This is because the new graft in April needs wood and bark to grow together with the rootstock before the buds begin to grow; therefore, dormant wood allows time for the connection. On the other hand, if dormant graftwood is collected for spring patch-budding, the collection should occur just before bud-break so that the buds will pop off the graftwood stick. Dormant graftwood should be straight one-year-old shoots and 1/4- to 1/2-inch in diameter. In cases where graftwood of a rare variety is needed, two-year-old shoots can be used. Young, fast-growing trees or de-horned mature trees make excellent dormant graftwood sources. Store at 45 degrees F. in poly bags, with very little moisture in the bags. The wood needs to be transported to the field in ice chests. Graft sticks can be used for one year only, so label all grafts by variety and year. Throw away all old graftwood before putting new graftwood in the refrigerator.
A new shoot will grow from the graft bud in 4 to 6 weeks if the connection was successful. Care needs to be taken to prevent the new shoot from blowing out. Sometimes the graft shoot grows very fast, in which case it should be pruned back to only 18 inches or secured in place by tying it to a stake. Either support or pruning should be used until the graft grows to at least two-thirds the size of the rootstock. High winds (as in Texas) or birds lighting on a graft are sure blow-outs without support.
For publications about pecans and pecan grafting, please visit the AgriLife Bookstore at http://www.agrilifebookstore.org.
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