One of the most utilitarian trees I grow is the black locust. Black locust is a very polarizing tree, some people go running for their soap box screaming invasive while others see it as a blessing. At our farm we see Black locust as a perfect tree to grow from seed in our air prune beds.
To me and people in the know, black locust is the fence post, ruminant (not horses) fodder, windbreak, nitrogen fixing tree. Yes it will send out volunteer trees but managed properly it is hardly invasive. I grow Black Locust trees and a few other tree species from seed in air prune beds. Let’s discuss what an air prune bed is and why I grow certain trees in them.
What are Air Prune Beds
Imagine a wood framed box of soil suspended a foot off the ground by cinder blocks. The bottom of the box is not wood but 1/4 inch hardware cloth. The small holed hardware cloth keeps the soil from falling out the bottom of the air prune bed. The wire mesh on the bottom of the bed is essential. More on the later.
Why Air Prune Beds?
Air prune beds are great for growing trees with large root systems, especially tap rooted trees. The problem with growing trees with large root systems is that they are difficult to transplant without losing trees roots each time you dig them out.
Tree roots grow as they normally do until they hit the wire hardware on the bottom of the air prune bed. Once the roots hit the end of the bed, they are exposed to air. That root stops growing and sends out another root in another direction. This continues for the entire growing season. At the end of the season trees grown in these air prune beds have massive healthy root systems.
Transplanting
Trees grown in air prune beds have large root systems. They are also very easy to remove from the bed. The soil is so soft and fluffy that trees can almost be pulled out of the beds by hand. This makes for easy harvest and transplanting.
If you are interested in learning how we build our air prune beds check out this video!