Air Pruning Roots
How does air pruning work? In nature, a plant’s roots can grow wherever they please. In a container, of course, there’s a firm border to their growth space. Because of this, the roots will butt up against the wall and often continue to grow along it, creating the root-bound spiral shape so common in potted plants. The roots grow thick and intertwined, inhibiting nutrient and water access and possibly eventually strangling the plant. Air pruning containers, however, stop the root’s growth at the wall of the container so that instead of wrapping around the wall, it sends out offshoots along its length, creating a stronger, more dispersed structure with many more root tips for accessing water and nutrients. This is the ideal root structure for potted plants.
What is an Air Pot?
An air pot promotes this healthy root structure with just what you’d expect: air. Plants don’t want their roots to grow above ground, so when a root encounters the air, the plant stops its progress in that direction and concentrates its energy in other parts of the soil. There are many different types of air pruning containers on the market, and some gardeners even make DIY air pruning pots, but the basic concept of all of them is letting in airflow on the sides and bottom of the container to stop root growth around the edges and promote it inside the soil.
Some air pruning containers have simple lines of holes along the edges. These are effective but not practical for fine potting material. Some are made of fabric and are suited to fine potting material but awkward for transplants. Some are plastic grids surrounded by perforated sheets that actually require some assembly. These are very effective at air pruning roots and transplants but are also not ideal for fine material.
