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Hind's Black Walnut, also known as the Northern California Walnut, is a species of walnut tree native to northern California's riparian woodlands. Like other walnuts, Hind's Walnut is large and deciduous, with a broad crown of pinnately compound leaves and a single trunk of dark brown or gray bark that can be furrowed or smooth. Trees are somewhat drought tolerant, can live for 50-150 years, and tolerate temperatures down to -12° C. Although it is widely used as the rootstock for English Walnut (Juglans regia) trees, Hind's Black Walnut is classified as a Vulnerable species by the International Union for Conservation of Nature (IUCN). Only one native stand of the trees remains, and the species is threatened by the loss of its habitat to urbanization and agriculture. All walnuts need full sunlight to grow well. Walnuts are dioecious, meaning they have both male and female flowers on the same tree and are therefore self-pollinating. However, the flowers do not always bloom at the same time. This problem can be solved by planting another walnut cultivar upwind whose catkins shed pollen at the same time the female flowers of the primary tree are open. Walnuts, like Hickories, contain a chemical called juglone, which inhibits the growth of many other plants. They are also difficult to grow other plants with because mature trees use a lot of water and shade large areas around them. The plants listed as companion plants can tolerate juglone. Grafted trees will begin to produce fruit one year after transplanting. Trees grown from seed will take 8-10 years to begin bearing fruit and may not bear true to the parent if trees have been cross-pollinated. Direct seeding is most effective when seeds are sown outdoors in autumn. Winter temperatures will break the seed's dormancy. If starting from seed indoors, pre-soak, scarify, and cold-stratify before planting to break dormancy.
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