Root pruning, what is it?
As the name suggests, root pruning is the cutting of roots. It is done for different reasons than pruning the tops of plants. We have total access to the tops of plants. Axis to the roots of plants is much more limited. Roots grow differently from stems. Roots do not have buds. You can virtually cut anywhere on a root and it will “sucker” unlike many of the stems of trees and shrubs.
Why root prune?
The most common reasons for root pruning include controlling the size of the plant, slowing the growth of plants, initiate flowering, keep the roots closer to the trunk, keep the roots out of problem areas or creating problems.
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| This is a root pruning machine used in nursery practices for undercutting trees growing in the field under production.This machine is driven so that the young trees are undamaged as they pass under and between the tracks. The U-shaped blade is pulled behind this machine and undercuts the roots…root pruning… to make a bare root fruit tree that will transplant to the field with fewer losses. Photo taken by me at Dave Wilson Nursery www.davewilson.com |
Root pruning is commonly done in the nursery operations where trees and shrubs are grown to be transported for planting in a new location. Root pruning is common in bonsai to reduce the growth of plants and keep them small. Root pruning is done in some greenhouse operations for similar reasons to nursery operations.
If root pruning is not done and the top of the plant dies or is severely pruned back, then the top regrows again very quickly to its original size. Once it reaches this size, growth slows again. This is the plants way of reestablishing what we have called the root to shoot ratio of the plant. The plant “recognizes” the difference in size between the top growth and undisturbed root size. The plant directs its growth, the flow of carbohydrates and hormones, to the top of the plant at the expense of growth in the roots.
How can I use Root to shoot ratios?
If a plant is growing too rapidly and you want to slow it down, root prune it. Take a sharp shovel and sever the roots by pushing it through the soil and through the roots as deep as possible.
Do you want to keep the roots of plants from entering the septic tank or other problem areas? Root prune between the plant and the problem area. Root prune every 2 to 3 years.
Some diseases are transmitted from plant to plant when the roots fused together and what are called “root grafts”. This commonly occurred in American elm with the transmission of Dutch elm disease. Root pruning can isolate plants from trees that are carrying the disease. If an Apple or Pear tree dies from fire blight, root prune the area around the dead tree to prevent the transmission of the disease through root grafts.
When Retrofitting trees and shrubs from a lawn area to drip irrigation, consider root pruning these trees and shrubs to generate roots closer to the trunk were the emitters are placed.
Having trouble with the tree flowering? Try root pruning to create a new root to shoot ratio that might slow the top growth and induce flowering.