Scientific Name
Juglans regia 'Carpathian'
Many people call this tree English walnut, but botanists are quick to correct the name — it was never native to England. Its true origin is a bit complicated, partly because it has been cultivated since ancient times and spread widely across Eurasia. Most evidence points to a center of origin stretching from Iran through parts of Central Asia and into China, which is why it is more accurately called the Persian walnut.
The name “Carpathian walnut” comes from a population found in the Carpathian Mountains along the border of what is now Poland and Czechia. Seed from those trees helped extend its cultivation into colder regions, including areas where winter temperatures can drop to around minus 20°F. Even so, it has never been a consistently reliable tree in our climate and is often planted more for nostalgia than for dependable nut production. Its main weakness is timing. It tends to leaf out and flower early, which leaves it vulnerable to late spring freezes that can destroy flowers, tender foliage and even young twigs. Early fall freezes can also cause damage. Over time, this pattern can weaken the tree. Still, a few individuals persist, including the walnut near Carroll Hall, where its survival is helped by its north-facing location, which delays spring growth by keeping it cooler and shaded. Walnuts are far better suited to warmer climates, especially California, where most commercial production takes place.
The Persian walnut has large compound leaves, typically eight to 15 inches long, with five or seven leaflets. When crushed, the foliage has a mild, sweet aroma. The fruit is a smooth, round green husk about one and a half to two inches across, often dotted with tiny pale speckles and aromatic when handled. When left undisturbed, the husk eventually falls and splits open to reveal a thin-shelled nut with sweet, edible meat. At Regis, this natural process is rarely seen, since squirrels usually harvest the crop within a day or two of ripening.
The twigs are stout, with prominent terminal buds, and the bark is light gray, developing ridges and plates with age. In our region, trees may reach about 50 feet, which is the height of the current Colorado champion. More commonly, they remain smaller, such as the specimen at Carroll Hall, which stands around 30 feet and ranks among the largest in the state.