Juglandaceae

Walnut Family

Walnuts

***

FAMILY: Walnut family (Juglandaceae) – Juglans genus.

SPECIES: #1 Arizona or New Mexico black walnut (Juglans major (Torr.) A. Heller). #2 Texas or little walnut (Juglans microcarpa Berl.).

TO UTILIZE AS FOOD: Both species listed above produce edible nuts. Walnuts are remarkably nutritious, but shelling them requires some effort. Arizona and Texas walnuts have thick, fleshy, aromatic, protective husks that cling to the shells. Removing the husks is reasonably easy, but very messy. Gloves are recommended to prevent them from staining the hands. Husks eventually turn from green to yellow when the nuts are ready to harvest, which is usually around August or September. The ground may be littered with walnuts at this time. Arizona walnuts are about 25-40 mm in diameter (including the husks). Texas walnuts are slightly smaller. Actual nuts of both species are considerably smaller. The trees are “monoecious,” so nuts can potentially be found on any individual. After removing the husks, which was traditionally done by pounding them in a stream, the rock-hard shells need to be cracked to expose the nutmeat. Shells of Arizona and Texas walnuts, as well as those of black walnut (J. nigra) in the eastern United States, don’t merely surround the nutmeat, they weave through it like steel beams supporting a building. Shells of English walnut (J. regia), a commonly cultivated species native to Europe and Asia, don’t have these internal reinforcements. Once the messy husks are removed, Arizona and Texas walnuts can be cracked with a rock and the nutmeat can be picked out or sifted out of the fragments. Processing walnuts is labor intensive, but the nutmeat is very high in calories and well worth the effort. An alternative method is to focus on the oil rather than the nutmeat. Walnuts can be pounded while still in the shells, and then simmered in clean water to liberate the oil. They need to be thoroughly pounded, simmered for several hours, and then cooled. Oils rise to the surface where they can be skimmed off. Shell fragments sink. Nutmeat also tends to sink, but it’s more buoyant than the shell fragments. A large amount of walnuts is required to yield a meaningful amount of oil. Freshly harvested walnuts (husked, but still in the shells) are moist and need to be stored in a dry place where they can breathe. Otherwise, they will rot. Molds that affect walnuts can form dangerous byproducts called aflatoxins. Many types of aflatoxins can endure food processing techniques, so walnuts with visible mold should be discarded. Checking a few walnuts for signs of mold is wise. If mold is discovered, a different source of walnuts should be located. Shelled walnuts are more perishable than unshelled walnuts, but they’re also more convenient. Freezing is recommended for long-term storage, but the nutmeat should keep for several months if stored under cool, dry conditions. Delaying the shelling process until the cooler temperatures of winter prevail is a good strategy for achieving the ideal storage conditions in a natural setting. Overall, Arizona and Texas walnuts, as well as those of other species, are excellent wild foods.

NOTES: Walnut trees contain a defensive compound called juglone. This compound is a germination inhibitor released into the soil by the roots, leaves, and hulls to prevent seeds of competing vegetation from germinating. Although it’s toxic to seedlings (except for walnut seedlings) trying to grow in the vicinity of walnut trees, the amount (if any) present in the nuts is not a concern to foragers. Healthy nuts are safe and nutritious, and there’s a long history of consumption to verify that. Walnuts were an important resource for native people throughout the range of the various species. The Arizona and Texas walnuts I gathered and described above were primarily from the Pinaleno Mountains in southern Arizona and Pinos Altos Range in southern New Mexico, where modern-day foragers can still find these age-old wild foods. 

A 100 gram serving of dried black walnuts (Juglans nigra) contains: 618 kilocalories, 4.56 g water, 24.06 g protein, 59.00 g fat, 9.91 g carbohydrates, 2.47 g ash, 61 mg calcium, 513 mg phosphorus, 201 mg magnesium, 2 mg sodium, 523 mg potassium, 3.12 g iron, 3.37 mg zinc, 1.36 mg copper, 3.896 mg manganese, 17.0 μg selenium, and other nutrients, especially essential fatty acids. Source: USDA National Nutrient Database for Standard Reference.

IDENTIFICATION: The Juglans genus is represented by about 10 species in the United States, of which only 2 grow in the Southwest. Walnut trees are mainly found along mountain streams.

Description of Arizona walnut (Juglans major): FORM thornless tree up to 20 meters tall; LEAVES compound; alternate; odd pinnate; leaflets 9-17, lanceolate; margins serrated; surfaces hairless or with a few glandular hairs; FLOWERS appearing before the leaves; sepals 3-6; petals absent; MALE flowers arranged in long hanging catkins; stamens numerous; FEMALE flowers tiny, ovary inferior, located near the branch tips, and arranged individually or 2-3 in clusters; FRUITS nuts contained within hard globe-shaped shells surrounded by fleshy husks; the husks 25-40 mm in diameter; the shells 15-30 mm in diameter and grooved; HABITAT riparian areas from Arizona to Texas; blooming in late spring. NOTES: Texas walnut (J. microcarpa) of the southern Great Plains and New Mexico differs primarily by having smaller leaves and nuts.

REFERENCES: #1 Arizona walnut (Juglans major): nuts Austin (p. 157), Couplan (pp. 71-72), Hodgson (pp. 196-198), and Moerman (p. 131). #2 Texas or little walnut (Juglans microcarpa): nuts Austin (p. 157) and Elias (p. 247).