New Research Demonstrates the advantages of growing with the Air-Pot system.

Air-Pot system the only container to completely eliminate root circling and accelerate growth – by up to 60%.

Two sets of recently published research from Holland and Germany, have found that the British designed and made Air-Pot container was the only type of pot to entirely eliminate root circling, and that the resulting healthy root system lead to better tree health and faster growth.

In the Dutch trial, independently verified by Cultus crop research, trees grown in Air-Pot containers were found to grow up to 60% faster than those in the open field.

In the German trial conducted by Dr Axel Schneidewind of Saxony-Anhalt State Office for Agriculture and Horticulture, five different containers were used to assess the development and impact of circling roots on Tilia, a species of landscape tree commonly planted throughout Europe. Only Air-Pot containers did not cause root circling. Circling caused by the other four containers negatively impacted the health and growth of the trees, both in the nursery and after they had been planted into the landscape.


Holland trial 2018-2019

In 2017 Carpinus, Tilia and Liquidambar trees were grafted, and then spent a year in the Air-Pot U system, ensuring that they started with a healthy root structure. In October 2018 a third were planted in the field and the others in either 7.5litre or 45litre Air-Pot containers. In both sizes of Air-Pot container the trees put on more growth than in the field, with the greatest difference in the 45 litre.

Download the independent report (.pdf, 451kb)

Twenty months after grafting the Liquidambar trees were over four metres tall with a girth of ten centimetres.

This exceptional rate of growth makes it possible to take a year out of production time, allowing a 50% increase in turnover from the same area of land.

The trial is ongoing with the trees in the 7.5 litre Air-pot containers potted up to 100 litre containers and the trees in the 45 litre containers left to grow for a second year. The second set of results will be available late Autumn 2020.

Trial comparing growth in Air-Pot containers to growth in the field
Holland 2018-2019


German trial 2008-2019

Starting in 2008 Tilia were grown in five different types of container – standard hard walled tub, Pot-in-Pot, Plantinbag®, Arbro-Perf® and Air-Pot®. Over three years their roots were regularly assessed for root circling and deformity. All of the containers showed some level of damage to the roots apart from the Air-Pot container where no circling roots were found.

Number of circling roots found in the different container types

In 2011 the trees were planted into the landscape where their roots and growth continued to be assessed for a further eight years.

Download the independent report (.pdf, 1.5mb)

After four years

One tree from each pot type was dug up and the roots examined. In the photographs you can see that the Air-Pot grown tree continued to develop a healthy root structure. The root deformities on the trees from the other types of container have got worse.

Tree taken from the Hard Walled Plastic Tub after 4 years growth in the field.
Tree taken from the Pot-in-Pot after 4 years growth in the field.
Tree taken from the PlantinBag® after 4 years growth in the field.
Tree taken from the ARBRO-Perf® after 4 years growth in the field.
Air-Pot grown tree after 4 years growth in the field showing healthy radial root development.

After eight years

Five trees were again dug up and examined. Once again the tree from the Air-Pot container has heathy normal root structure. On all the others the root deformity has got even worse, threatening the health and stability of the trees.

Eight years after planting the tree from a standard plastic tub has girdled the tree and is threatening its stability.
After eight years in the ground this tree grown in Pot-in-Pot container shows severe root deformity.
After eight years a tree grown in a Plant-in-Bag® container showing root deformity that will threaten the health of the tree.
After eight years the tree grown in an ARBRO-Perf® container demonstrates how the root deformity has got much worse over time.
Eight years after planting the tree from an Air-Pot container continues to show healthy radial root development.

The root deformity has also clearly affected the trees’ rate of growth. On average the Air-Pot grown trees, which had no root deformity, put on 46% more growth than those grown in the other types of pot.

The results have surprised academics and growers alike. Although the detrimental effects of root circling, which come from growing in all standard containers, have long been recognised, the extent of the benefits of growing in Air-Pot containers had not been independently confirmed in trials.

Tony Kirkham, head of the Arboretum at Royal Botanic Gardens Kew is one of the system’s greatest champions and comments:

“When you buy a car, it’s important to look under the bonnet and see the engine. A tree is no different – it is the root system which powers the growth of the tree. Look after the roots first to secure the long-term survival of the tree. That is what the Air-Pot container does, it develops radial, healthy roots to ensure that trees thrive for generations to come.”