Pignut with husk partly gone, Oct 2023 (photo by Kate St. John)

15 November 2023

The Nutty Series: Pignut hickory

Different species of hickory nuts look the same … but not quite. This one, partially in its husk, was a puzzle so I brought it home. Husks and shells together provide the clues so I had three nuts to work with in various stages of undress, plus a table of southwestern PA hickory husk and shell characteristics.

Pignuts in husk, shell with insect hole, partially in husk, Nov 2023 (photo by Kate St. John)
Characteristics of Southwestern PA Hickory Husks and Shells
Common NameScientific name
Shagbark HickoryCarya ovataNearly round, 1.75", thick, green, splits to baseNut has 4 ribs
Mockernut hickoryCarya tomentosaOval to pear shaped, 1.75", green, husk is thinner than shagbark's, splits to baseNut is thick-shelled with 4 ribs
Pignut hickoryCarya glabraOval or slightly pear shaped, 1.5", thin husk green to tan, maturing to da
rk brown, usually splits only partway to base
Nut has no ribs
Bitternut hickoryCarya cordiformisVery thin rough husk with 4 wings, splits only to the middle as if it is peeling off the shellNut is round, small and thin-shelled with a pointed tip

The Verdict: The photo was taken after the nuts sat indoors for three weeks. The husk is still pear shaped but has turned brown and splits completely. Hmmm. The nut, however, has no ribs so I’d say this is a pignut.

Sliced open it would look like this. I lack the tools to make such a clean cut.

Pignut sliced open (photo by Rebekah D. Wallace, University of Georgia, Bugwood.org)

Pignuts were too bitter for European settlers so they fed them to their pigs, hence the pignut name. However pignuts are prized by wildlife including chipmunks, squirrels, mice, blue jays, red-bellied woodpeckers and wild turkeys. If deer eat them they will soon disappear from the ground in Pittsburgh’s parks.

Pignut hickories (Carya glabra) range along the east coast (the original colonies) all the way to the Mississippi Valley and down to the Gulf of Mexico but don’t normally grow in northern Pennsylvania.

Pignut hickory range (map from Wikimedia Commons)

In winter they are best identified by their buds. As with all hickories, the end bud is larger than the side buds but on the pignut it is relatively small and the side buds are almost at right angles to the twig. This one is about to burst into spring leaves.

Pignut hickory buds (photo by Chris Evans, University of Illinois, Bugwood.org)

Young trees have smooth bark. Mature ones have these ridges.

Mature bark on a pignut hickory (photo by Rebekah D. Wallace, University of Georgia, Bugwood.org)

The tree’s compound leaves have 5-7 serrated leaflets …

Pignut on the hickory tree (photo by Franklin Bonner, USFS (ret.), Bugwood.org)

… which turn a beautiful golden color in the fall.

Pignut hickory in autumn (photo by T. Davis Snydor, The Ohio State University,Bugwood.org)

But now the trees are bare.

Bare pignut hickory (photo by T. Davis Sydnor, The Ohio State University, Bugwood.org)

Bonus! Did you notice the clean hole in the center nut in my three-nut photo? It was probably made by a pecan weevil (Curculio caryae). The weevil drills a hole to lay its eggs inside developing hickory nuts, including pecans.

Pecan weevil drilling into a husk (photo by Jerry A Payne, USDA Agricultural Research, Bugwood.org)

How does she drill into the nuts? Check out this video of acorn weevils drilling and mating.

Read more about pignuts at the Glen Arboretum.

(credits are in the captions)

One thought on “Pignuts

  1. When my daughter was young, we were walking in the woods with some friends, and there was a half a nut shell pressed into the ground cut side up so that it looked kind of like the end of a pig’s snout, and one of our friends told my daughter that it was a pig hibernating underground, and he left his nose exposed so that he could breathe. Not a good way to teach kids about nature 🙂

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