Persian walnut, better known in the US as English walnut, is the tree behind most walnuts sold in grocery stores. Native to the mountains of southwest and central Asia, it has been planted for thousands of years and was brought to the Americas by Europeans in the 1600s. It is not native to the US, where it is grown mainly in orchards, especially in California, and in yards.
Appearance
- Growth form
- Large deciduous tree, 33–80 ft (10–25 m) tall, with a broad rounded crown. Young bark is smooth and silvery gray.
- Leaves
- Compound leaves about 10–12 in (25–30 cm) long with usually 5–9 leaflets (most often 7). Leaflet edges are smooth, and the three leaflets at the tip are the largest.
- Flowers
- Male flowers hang in catkins 2–4 in (5–10 cm) long; small female flowers sit at the branch tips in small clusters. Blooms in spring.
- Fruit
- A round fruit 1½–2½ in (4–6 cm) across with a green husk that splits in fall, revealing the familiar wrinkled brown nut.
Look-alikes
Eastern black walnutJuglans nigra
Black walnut has 15–23 toothed leaflets per leaf, versus 5–9 mostly smooth-edged leaflets on English walnut. Its husk clings tightly to a thick, very hard shell.
Why they get mixed upBoth are large walnut trees with similar round green fruit.
Where it lives
- Typical habitats
- Orchards
- Yards and parks
- Range
- Not native to the US. Grown mainly in orchards, especially in California's Central Valley, and planted in yards elsewhere. Its wild range is unclear because of long cultivation, but it probably comes from the area around Afghanistan, Pakistan, northwest India, and Tajikistan.
- Preferred conditions
- Does best in deep, rich soil with full sun and long, warm summers. Hardy in USDA zones 6–9.
Growing it
- Care
- Most varieties shed pollen and receive it at different times, so planting two compatible varieties helps with pollination. In North America, root diseases are a problem, so orchard trees are normally grafted onto 'Paradox' hybrid rootstock.
Name and classification
- Varieties and forms
- 'Carpathian walnut' is a group of cold-hardy strains with good nuts, not a separate species.
Conservation
- IUCN Red List
- LCLeast ConcernLow risk of extinction
- Threats
- In California, the walnut husk fly (Rhagoletis completa) lays eggs in the husks; the maggots mostly stain the shells, though early attacks can spoil the kernels.
Culture and stories
- Culture and stories
- Early American settlers called it 'English walnut', apparently to tell it apart from the native black walnut and butternut; some writers think the name was simply a mistake. 'Persian walnut' points to its origins in Iran and Central Asia.
- Its fallen leaves and husks contain juglone, a natural chemical that keeps many plants from growing beneath walnut trees.
- The green husk makes a brown dye, and the dark heartwood is prized for furniture, flooring, guitars, and gunstocks.
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