Members of the walnut family have large aromatic leaves, that are usually alternate, but opposite in Alfaroa, Oreomunnia. The leaves are pinnately compound, or ternate, and usually 20-100 cm long. The trees are wind-pollinated, the flowers usually arranged in catkins. Hickory nuts (Carya) and Walnuts (Juglans) in the Juglandaceae family grow within an outer husk; these fruits are technically drupes or drupaceous nuts, and thus not true botanical nuts. Tryma is a specialized term for such nut-like drupes.

There are eight genera in the family, including the commercially important nut-producing trees: walnut (Juglans), pecan (Carya illinoinensis), and hickory (Carya). The Persian walnut (Juglans regia) is one of the major nut crops of the world. Walnut and hickory are also valuable timber trees.

Scientists at the National Center for Atmospheric Research (NCAR) at Boulder, Colorado, have discovered, by accident, Walnut trees may get "headaches." As reported in the scientific journal Biogeoscience, instruments set up near a grove of walnut for monitoring air pollution showed that at certain times, the trees emitted methyl salicilate, a form of acteylsalicylic acid, or common aspirin.

These emissions corresponded periods of prolonged droughts or large temperature fluctuations, stressful events for any type of plants, but for trees in particular. The scientists believe the aspirin-like chemicals trigger the production of proteins that boost the tree's immune system to help ward off disease.