Jens Lindworsky9. May 2019
Bonsai pots with air pruning prevent harmful circling roots. Specially shaped holes guide the roots out of the pot once they reach the inner wall. This stimulates the growth of lateral roots.
This is how the pot does the root pruning - gently, continuously and without human intervention.
Well branched roots, no overly long roots
This field maple was in a Tie Pot with Air Pruning for a year. For the photo, the roots were slightly loosened but not trimmed. The root ball is compact and intensely branched. Such a root system is efficient and easy to repot.
This pine was in a normal pot for two years. Long, poorly branched circular roots have grown along the pot wall. These roots send out stress hormones and slow down photosynthesis. When repotting, a large part of the roots must be removed.
The special Air Pruning holes direct the roots outwards so that they cannot grow in circles. This effect does not occur in normal bonsai pots. There the roots grow past the holes or skip them.
These roots grew out of the pot through an Air Pruning hole, the tips have dried up. Now plant hormones are released which stimulate the growth of fresh lateral roots.Roots can only absorb water and nutrient salts in the area of the root tip. So with bonsai it is particularly important that the root ball has many active root tips.
On the left a root that has grown along the wall of the pot. Stress hormones have suppressed the formation of lateral roots. This root has little active root tips.The root on the right has grown unhindered in the substrate without contact to the pot. It is well branched and has many fresh tips. This means that it can absorb water and nutrient salts much better. Both roots are from a pomegranate.