Have you ever pulled a plant out of a pot and seen all of its roots matted on the bottom of the pot? Have you ever wondered why this happens?
When roots grow to the edge of a plastic pot, there is a small layer of water and nutrient between the medium and the walls. As roots’ sole purpose is to hunt out food and water, the plant is tricked into thinking there is still space for it to grow even while it’s wrapping around the edges of the container. The roots that are circling around the inside of the edge are more susceptible to excess heat, drought, and disease.
Roots also seek oxygen, just as much as they seek water. Most gardeners don’t realize the importance of both in healthy plant growth. In a plastic pot, the only source of oxygen near the root system are the holes punched at the bottom. The primary roots of the plant grow to the very edge of the pot, instead of evenly throughout the middle of the soil, as they seek the air. They keep swirling around the inside of the pot, growing longer and longer. The more that they twist and grow, the less healthy they become. Some may even start to turn brown and to die off.
How can you avoid all of these problems…? Air pruning.
Air pruning is a technique that exposes root tips to relatively dry air, thus stopping their growth. The plant now realizes its boundaries and focuses on creating secondary roots that branch out from the originals within the growing media. These secondary roots then spread throughout the media until they reach the thin layer of air at the walls, and the cycle is then repeated. Over and over your plant is producing smaller, more fibrous roots, filling up its container. More root hairs = more root tips, and more root tips = more water and nutrient uptake. In short, the overall effect of this growth and pruning cycle is the creation of a well-developed root system in a relatively short amount of time.
How do you air prune…? Special pots
Smart pots are the most common air pruning pots. They are made out of stiff fabric and take the shape of a regular plastic pot. Since the Smart pot is fabric, the roots can easily grow through the material and come out the other end, allowing for the air pruning to take place.
A few types of air pruning containers:
- Fabric Pots – Made from non-woven polypropylene material. Allows heat to escape via breathable material. These pots are highly durable (about 5+ years of continuous use) and many sizes come with handles!
- Air Pots – A black plastic container with an unusual design – inward and outward-pointing cones resemble egg carton. The bottom is a plastic mesh. These containers are highly durable and can be taken apart for storage.
- Winstrip Trays – 72 cell propagation trays with an open design that enables air pruning in the early stages of plant life. Highly durable polypropylene plastic is UV resistant and usable for 10-15 years.
However, in air pots or smart pots, plants need to be watered about twice as often as regular containers since the grow medium is constantly drying out from the sides. This seems to be the only downside to air pruning containers.