September 2024: Northern Pecan

Pecan trees at The Arboretum State Botanical Garden of Kentucky, Lexington, Kentucky

Located along the path through the Bluegrass Region at The Arboretum is a stand of Pecan (Carya illinoinensis) trees. Also known as Northern or Hardy Pecan, this tree is actually a species of hickory in the walnut family (Juglandaceae). Pecans have a wide natural range that spans throughout the Midwestern and Southern United States and then south into Northern Mexico. Kentucky is located along the Northeastern extent of its range and the species is only found in major river floodplains along the western portion of the state. Pecan is derived from an Algonquin word ‘pacane’ referring to walnuts and hickory nuts as

well as pecans.

It is one of the largest species of hickories growing 60 to 120 feet tall with a canopy spread of 35 to 75 feet. The compound deciduous leaves are alternately arranged, 12 to 18 inches long, with 9 to 17 leaflets arranged in a pinnate manner. Each leaflet is 2 to 4 1/2 inches long and 1 to 2 1/2 inches broad. The leaflets possess an unusual sickle-like (falcate) shape which is distinctive from other species of hickories.

Leaf of pecan tree.

Pecan trees are wind-pollinated and have a unique flowering system that prevents self-pollination. These trees produce separate male and female flowers on the same plant. The male flowers, called catkins, bloom on previous year's growth, while the female flowers appear on the current year's branches. To ensure pollination, at least two pecan trees are needed. Different cultivars can improve fruit quality and yield.

To prevent self-pollination, pecan trees have evolved two flowering patterns: protandrous and protogynous. In protandrous trees, the male flowers release pollen before the female flowers become receptive. In protogynous trees, the female flowers are receptive first. This ensures that pollen from one tree can fertilize the flowers of another. Seed-grown trees have an equal chance of being protandrous or protogynous, so planting named cultivars is recommended to guarantee successful pollination. Locally, those interested in learning more about pecan trees can find the group Kentucky Nut Growers Association, which has an annual meeting, grafting workshops, and more.

Pecans cradled in a hand.

Like all other members of the hickory genus, pecans are not truly a nut but technically a drupe, which is a fruit with a single stone (or nut) surrounded by a husk. The husks are produced from the exocarp tissue of the flower while the nut develops from the endocarp and contains the seed. The green outer husk turns brown at maturity when it splits off into four sections to release the thin shelled seed. Before European colonization, pecans were a staple food crop of indigenous peoples in the Mississippi River valley and the valleys of its principal tributaries.. In the 16th century Spanish conquistadors were first introduced to pecans through their interactions with indigenous peoples in what is now Louisiana, Texas, and North Eastern Mexico. In 1927 the National Pecan Growers Association designated the official and correct pronunciation as PEA-CON.

A large pecan tree graces the front of a residence next to the driveway. Photo by Dave Leonard.

The Kentucky Champion Pecan Tree is located on private property in Fulton County and stands 116 feet tall with an average crown spread of 112.5 feet, and a trunk just over five and a half feet in diameter. The National Champion grows in Isle of Wight County, Virginia and is over 97 feet tall with a crown spread of 106 feet. Despite the overall smaller canopy size, this tree is multi stemmed and the two massive trunks have a combined circumference of 293 inches and a total diameter of almost seven and a half feet.

Photos 1-3 by Greg Doyle, photo 4 by Dave Leonard.