The pecan tree, Carya illinoinesis, is a native American tree that was known as a food item by the ancients as early as 3000 to 6000 BC, according to recent cave excavations unearthed by archaeologists in Texas. The pecan nut was widespread and used by the mid-American Indian tribes into other territories long before the arrival of the Mayflower. This thin shelled nut is easy to collect from underneath pecan trees after the nuts begin ripening in the fall, and the presence of the soft shell elevates the pecan attractiveness above the hard shell hickory nut or the walnut. The spicy sweet flavor of the kernel is exceptionally tasty if the nuts are eaten before temperature warmups during the late spring or early summer. Otherwise, the pecan nuts can retain their sweet flavor for years if frozen or kept in cold storage.
The native nuts of the pecan are quite variable in nut size and shell thinness. In the commercial trade, these native nuts of the pecan are called a seedling pecan.” The size of these nuts can mature to the size of a rifle BB or may in some cultivars grow to the size of a 12 gauge shotgun shell. Large pecan nuts can number 40 to 50 per pound before shelling and some improved papershell pecan cultivars will shell out more than 50% kernel.
The pecan tree commercial production today is classified into two categories by buyers: seedling and cultivar. The seedling market brings a lower market price than the cultivar, because the kernel shell out is so unpredictable to the shelling plant buyer. The quality and shell thinness is also very variable for seedling pecan tree production.
Technically, the cultivar is actually a pecan seedling, but it is an outstanding seedling that is grafted or budded so that a large orchard of pecan trees can be grown with the nuts having a predictable outcome of the nut size, nut quality, disease resistance, thinness of shells, and many other desirable characteristics.
If a pecan tree is grown from a seed, regardless of whether the nut planted was a pecan seedling or a named pecan cultivar such as Stuart, Desirable, or Elliot, the pecan tree that grows from that seed will be unpredictable, insofar as the resulting pecan crop that is produced. The tree grown from such a sprouting seed may even be ultimately sterile and incapable of producing nuts at all. Pecan growers often agree that only a grafted pecan tree should be planted in commercial orchards. There are orchards (groves) of wild pecan trees (seedling) harvested in Texas, but the inferior seedling trees were systematically removed over the years in order to make the nut growing operation profitable and to make room for exceptional seedling groves of native trees that bear large quantities of pecan nuts profitably.
Extensive collections of exceptional seedling pecan trees began in the 1800’s and grafting clones and the the naming of superior pecan cultivars such as Alley, Mobile, Schley, Columbia, and Russell began a frantic rush to establish and grow these pecan cultivars as commercial orchards. Most of the original cultivars that were profitable 100 years ago have been discontinued except for the Stuart and a few others, because better cultivars have been introduced and many of the old pecan cultivars have become susceptible to the attacks of fungi and insects, and some of the older cultivars tended to overbear” that resulted in tree limb breakage or a shift to unpredictable, alternate year bearing so that some years no nuts were produced at all.
Because extensive literature has already been published in the past on cultivar descriptions and characteristics, this article will not discuss that topic except to say that only 8 to 10 cultivars of pecan trees are recommended today for planting in commercial orchards. Research by USDA scientists points to the fact that cultivars that were hybridized from Western pecan progeny are often not grown satisfactorily in the South and the East, because of the high humidity and temperatures promote fungal and bacterial growth on leaf parts and nuts that drop off the trees prematurely. Mr. Louis D. Romberg of Texas performed numerous hybridizations of pecan nuts in the last mid-century, many of which were found to be highly productive in the Western States but unworthy in the South and East. The standard pecan tree cultivars that are grown in the South show good performance in the West where the humidity is low. Pecan trees are capable of intercrossing with hickory nuts, a close genetic relative, and the old Nelson” and Columbia” pecan cultivars were reported to be hybrid nuts of the pecan and hickory nut parents, called the Hican”. The commercial hican cultivars of Pee Wee” and Simpson” hican are available to buy on mail order nursery websites. Other natural hybrid nuts that have resulted from intercrossing pecan nuts with hickory nuts have been reported in literature.
Other reported crosses of the pecan nut tree, Carya illinoinesnsis, with various other species of hickory nut trees have resulted in hybrid pecans of water hickory, Carya aquatica; Shellbark hickory, Carya ovata. It is not clear what specific species, shagbark or hickory, or shellbark hickory was crossed with the pecan that resulted in the present day 2 cultivars of hican nut trees.
It is not unreasonable to assume that pecan, Carya illinoinensis, could also by hybridized with two wild species of hickory trees, the Mockernut Hickory tree, Carya tomentosa and the Pignut Hickory tree, Carya glabra. Various rootstocks of the Juglans and Carya genus have been found to be compatible with grafts of the pecan budwood. Various species of walnut trees of the genus, Juglans and the genus, Carya to include hickories have been successfully used to dwarf pecan trees, but most pecan nursery operations today only use rootstock obtained from planting pecan seed from cultivars such as Moore and Curtis.