Carya illinoinensis Seeds | Pecan
LATIN NAME: Carya illinoinensis
COMMON NAME: Pecan
Plant Profile
The word pecan comes from an Algonquian term for a nut that had to be cracked with a stone, and for most of its history that was an honest description. Wild pecans from the bottomlands carry a shell thick enough to defeat a thumbnail. The peoples of the Mississippi valley pounded the kernels into a milky mash called pawcohiccora, and that dish is the root of the word hickory. The orchard pecan is a different creature: selection has produced nuts thin enough to break in the hand, and it is now the most widely planted nut tree in the walnut family, grown far beyond its homeland.
Two problems dominate the crop. Pecan scab blackens nuts and defoliates trees in wet summers and is far worse in the humid Southeast than in the drier West. The pecan weevil is the second: the adult drills through the immature husk, the larva feeds inside the kernel, and when the nut falls the grub chews out and buries itself in the soil, where it may wait for two or three years before emerging. Named cultivars such as ‘Stuart’, ‘Desirable’ and ‘Pawnee’ differ sharply in shell thickness and nut size.
Pecan wants space, deep soil and summer heat. A mature tree casts heavy shade and sheds husks, catkins and nuts, so put it at the far end of a big garden or in an orchard row a mower can reach under.
Science & Biotechnology
Pecan sits in Carya section Apocarya, a group marked off from the true hickories by a clean cytological signal: pecan and its relatives carry thirty-two chromosomes in their body cells, while the shagbark and mockernut hickories of section Carya carry sixty-four. The husk differs too, splitting into four valves along winged sutures so that the ripe nut drops free once it dries. This is a large tree on a good bottomland site, with a deep taproot and a trunk that darkens and furrows with age.
Each pinnate leaf carries nine to seventeen sickle-shaped leaflets on one rachis, finely toothed and glandular, and the crown turns soft yellow before leaf fall.
Pecan is monoecious. Staminate catkins hang in threes from the previous season’s wood, while the pistillate flowers sit in short spikes at the tip of the current shoot. The two kinds usually mature on different schedules, a condition called dichogamy: some cultivars shed pollen before their stigmas are receptive, others are the reverse. Orchard planters mix the types so pollen is always in the air.
The kernel is roughly seventy per cent oil, mostly oleic acid with a large fraction of linoleic acid, and it is the richest common tree nut in gamma-tocopherol. That profile is why a shelled pecan goes stale quickly in a warm pantry: the polyunsaturated fraction oxidises and the nut begins to taste of cardboard. The brown seed coat, the pellicle, carries most of the phenolic load, including gallic acid, ellagic acid and condensed tannins, and it is the part shellers work hardest to remove, because a scrap left on a kernel turns bitter in baking.
Uses & Benefits
Pecan halves go into pie and praline in the American South, into butter pecan ice cream, and into confectionery in Europe. Kernels are best toasted briefly before use, which drives off moisture and deepens the flavour. Cold-pressed pecan oil is sold for dressings, and nut meal can replace part of the flour in shortbread. The shells, hard and clean-burning, are sold as blasting grit, as a mulch that resists compaction, and as mill fuel.
Growing from Seed
Pecan will not root from cuttings with commercial reliability, so clonal material is multiplied by grafting and budding onto seedling rootstock. Laboratories have pursued the alternative route, raising plantlets from immature cotyledons through somatic embryogenesis and from axillary shoot culture. Public breeding programmes in the southern United States use those tools alongside conventional crossing.
Pecan seed is short-lived once dry, so sow it in the autumn it ripens, or store it damp and cold. Set each nut about five centimetres deep, on its side, in a deep container or a nursery bed, using two parts garden loam, one part leafmould and one part coarse grit. The seed leaves stay underground while the shoot rises, and the first root drives straight down, so a shallow tray is useless here. Space nuts thirty centimetres apart in the row with ninety centimetres between rows, and screen the bed, or squirrels and jays will take the lot.
Seedlings vary, and a good nut comes true only when a cultivar is grafted. Raise the stock for a season, then graft while both scion and stock are dormant, using whip-and-tongue on pencil-thick wood, or patch budding in summer when the bark slips. Cut the stock back above the union and rub out every shoot below it.
Young pecans respond strongly to zinc, and a shortage shows as small mottled leaves crowded at the shoot tips. Water deeply at the drip line through the first two summers and let the ground dry between soakings. Train a central leader, remove the lowest scaffold limbs as the crown lifts, and thin a crowded top so light reaches the bearing wood. The tree is hardy into cold-winter regions, though a late frost after bud break can strip a year’s crop.
Our Take
If you have the room, pecan rewards patience better than almost any other nut, and a tree you sow may crop for a century. For a smaller garden or a colder site, look at the wild hickories, which are tougher and just as good in the kitchen: the pignut hickory for dry woodland ground, or the shagbark hickory if you want the sweetest kernel of the group. Growers planting for nuts and timber together often put a black walnut in the next row.
Related Reading
More species in the same orbit as Pecan: