Root culturing is one of the most important nursery operations because a tree seedling is only as good as its root system. During the latter part of the first growing season, seedbeds are undercut with a horizontal blade to severe the dominant tap roots and promote a more fibrous root system. Wrenching is a special type of undercutting that uses an angled blade to shatter the soil profile, and increases the soil permeability and aeration. Wrenching also induces a temporary seedling moisture stress which can be used to retard shoot growth and induce dormancy.
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