All nut trees at Tambourine Tree Nursery are grown in air-prune beds or in air-pruning band pots. All our pawpaw trees are also started in air-prune beds. Trees started from seed in an air-prune bed have a better chance of surviving transplanting than trees grown in standard beds – especially for trees that have sensitive and/or long taproots.
Our air-prune beds are similar to a standard raised bed. Instead of resting on the ground, the bed is lifted and hardware cloth is fastened to the bottom. We have air-prune beds that range in size from 1′ x 2′ to 3′ x 24′ and all are lifted off the ground about 2″-4″.
When a tree seed germinates, it sends a taproot down into the ground before any sprout is seen above ground. The purpose of this taproot is to reach water and nutrients deep in the ground, helping the tree become established. Some taproots can reach 3 feet or more. Trees with large taproots are notorious for having a low survival rate upon transplanting – it is tough to dig out a long taproot without breaking it, and to dig a hole big enough for the taproot.
When a taproot hits the bottom of an air-prune bed it reaches the air and cauterizes itself (a taproot from a tree grown in an air-prune bed will be as long as the bed is deep – usually 8″ to 1′ long). The plant’s response will be to focus on fibrous secondary root growth instead of continuing to grow the primary taproot. The shorter taproot along with more fibrous feeder roots will improve the tree’s abilities to survive upon transplanting. A tree will sever off its taproot within few years, meaning if the tree is taken care of during this time (with some supplemental watering and mulch), it will not be missing an integral part for the future.