Tolerances for total and special defects are specified for each grade. Your USDA zone indicates the lowest winter temperature in your area, but walnuts also require a specific number of hours between 33° and 45°F (33° and 45°F (0.55° and 7.2°C). Once shelled, walnut kernels are physically inspected to ensure an end product that is clean, well-dried, and of specified color, as determined in comparison to the official walnut color chart. The black walnut grows to a height of 50–75' and a spread of 50–75' at maturity. The California Walnut Commission, established in 1987, is funded by mandatory assessments of the growers. Although many varieties of walnuts are grown in California, six varieties account for over 85%: Chandler, Hartley, Howard, Tulare, Serr, and Vina. American Heart Association® Heart-Check Mark Certified Recipes, Walnut Recipes and Male Reproductive Health. All Rights Reserved. Although English and black walnuts grow in USDA plant hardiness zones 3 through 7 and 4 through 9 respectively, there’s much more to their climate story. Commercial product meets the same high standards of quality as those sold directly to the consumer. Technically, these are called chilling hours. If you plan to grow walnut trees in high altitude, you can select spots where cold air masses can escape easily, or use late varieties, which sprout well after the frosts. But, because walnut buds don’t bloom until their second summer, many never reach the harvesting stage. 11 Answers. (Partally self-fertile, plant multiple trees to ensure pollination) (zones 4-9) Alleopathy is the term given to the suppression of growth of one plant species by another due to the release of toxic substances. Half of that water (25 inches) should come between June and August, so you’ll have to provide what Mother Nature doesn’t. 600 chilling hours. They grow all over the US. How Do Almonds Grow? In reality, they won’t flower without a whopping 1400 of them. When grown in the open, the black walnut reaches 75' tall with a round, low branching, open crown that spreads nearly as wide as it is tall. Is self-fertile but requires wind for pollination. A partial list includes tomatoes, potatoes, peas, peppers, cabbage, alfalfa, serviceberry, chestnut, pine, arborvitae, apples, blueberry, blackberry, cherry, azalea, rhododendron, lilac, hydrangea, privet, members of the heath family. Inshell walnuts are sized as jumbo, large, medium, or baby according to USDA standards. Features pinnately compound, alternate leaves that are 12–24" in length and consist of 15–23 dark green leaflets that are 2–5" long. After a walnut sapling is planted, it takes five to seven years for it to grow into an adult tree suitable for harvesting. Why does this happen and what’s a walnut grower to do? A walnut orchard can take a few years to come into full production, but then produces up to 6,000 pounds of nuts per acre. This native tree has been called our best friend in times of war and peace. Cracking the Secrets of Walnut Harvesting. The Board is funded by mandatory assessments of the handlers. Handlers also meet individual customers’ standards and specifications. After a walnut sapling is planted, it takes five to seven years for it to grow into an adult tree suitable for harvesting. Black walnut tree roots contain juglone, a toxic substance released when the the roots of other juglone-sensitive species come in contact with walnut roots. There must be ten of them on my two city lots. And during summer, prolonged temperatures of 100°F (38°C) or higher harm the fruit and reduce the size of the walnuts. 300 chilling hours. Find out about the process from tree to table, and the strict food quality and safety standards that regulate the walnut industry.