Sweet Chestnut Tree Growth
The sweet, or Spanish, chestnut (Castanea sativa) is a large deciduous tree cultivated for millennia in southern Europe for its starchy edible nuts. It can be grown in U.S. Department of Agriculture plant hardiness zones 5 through 8. When American gardeners refer to sweet chestnuts in the landscape, it usually is the Chinese chestnut (Castanea mollisima), a similar species that is cultivated more commonly in the United States and can be grown in USDA hardiness zones 4 to 8. The American chestnut (Castanea dentata) is virtually extinct in its native range in the east after a devastating blight was introduced in the early 1900's, but it occasionally is grown in western landscapes in USDA zones 4 to 8.
The European and Chinese species are large, spreading forest trees that can grow 70 to 100 feet tall and 50 to 70 feet wide. In spring, showy yellow catkins hang from the branches. They make an excellent shade tree, but the spiny husks that litter the ground can be a hazard. Chestnuts are moderately fast-growing trees if growing conditions are adequate. When grown for their wood, they can be cut nearly to the ground every few years. This practice is called "coppicing" and results in vigorous regrowth of numerous long, straight trunks.
Both types of chestnut are moderately drought tolerant once established, though young trees require weekly irrigation. They perform well in soils of moderate fertility, including sandy loam. Chestnuts are intolerant of alkaline soils, growing well in acidic soils with a pH between 4.5 and 6.5. They like hot summers and are well-adapted to arid environments and humid climates. The chestnut blight that wiped out the American species also affects the spanish chestnut, though the Chinese variety is fairly immune.
All chestnuts require a second tree for cross-pollination, though not all individual trees are capable of pollinating each other because of their variable bloom periods. A grove of several trees planted together ensures good production. Chestnuts ripen in October and are harvested after they drop to the ground. The sharp spines on the outer husk of the nut makes harvesting a bit difficult, requiring heavy gloves and tools to pry the nuts out of the husks.
Seedlings often are very productive, but only grafted trees reliably produce the same quality nuts as their parent. "Colossal" and "Nevada" are top-quality varieties, grown commonly in California, that are compatible pollinators. "Dunstan" chestnuts are a hybrid variety that is highly resistant to chestnut blight and produces large crops within 4 or 5 years. "Kelsey" has a more compact growth habit and is an option where space is limited.
Brian Barth works in the fields of landscape architecture and urban planning and is co-founder of Urban Agriculture, Inc., an Atlanta-based design firm where he is head environmental consultant. He holds a Master's Degree in Environmental Planning and Design from the University of Georgia. His blog, Food for Thought, explores the themes of land use, urban agriculture, and environmental literacy.