In the wild, walnut trees are propagated by seeds. However, in commercial walnut orchards, walnut trees are propagated by grafting or budding scions in rootstocks that have already been planted in the field. Professional walnut growers benefit from a tree that is a combination of two different plant tissues, the rootstock and the scion. The rootstock is the lower part of the tree and produces the root system. The scion produces the upper part of the tree and of course determines nut’s characteristics. In most US regions, walnut trees are propagated by budding the rootstock from August to September, while grafting can take place during spring and after the rootstock has produced some leaves. The walnut rootstocks are propagated mostly by seed. When we plan to grow black or English walnut rootstocks from seed, we shall either sow the selected seeds during autumn in the nursery or stratify them in sand for approximately 3 months (temperature 36-39°F or 2-4°C). Two common types of seedling rootstock are Northern California black walnut
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