Why a Pot Size Matters

By Millie Traynor

Choosing the correct pot size

As a hydroponic grower you have many factors to take into consideration. One of them being your pot size. Your pot size will affect the growth of the plant and roots.

To ensure your plants have the best indication to flourish there are three important areas namely space, temperature and the plant. When all these factors are combined this will help when choosing the correct pot size.


Pot size matters for two reasons:

A pot that is oversized will mean plants will remain in damp growing media for an extended period which means roots can suffocate, and if left, they can start to rot.

Pots that are oversized then allow the nutrient solution to evaporate before the plant has a chance to absorb all the nutrients it requires fully, therefore becoming wasteful and may also lead to further problems such as overwatering as the roots are not taking up all of the excess water.

Undersized Pots can quickly lead to plants becoming root bound and also mean they could take up the nutrient very quickly and may lead to underwatering problems.


Using diverse sized pots in a hydroponic system

Once a hydroponic system has been obtained, there is a limitation to how many pots you can use for the area you have accessible. This can be an increased restrictive if you are growing indoors and making use of grow lights.

A growing light can be the foundation, for each 600W of light, you should make use of 50-60 litres of growing media.

This can be suitable for pots which will be placed in a 1.2 meter squared growing bed. For a bed of this size, you can use the following as a guide as to what pot sizes will hold up this area.

  • 5-6 x 10L -growing pots.
  • 4 x 15L -growing pots.
  • 2 x 30L - growing pots.
  • 1 x 60L - growing pot.

What if I am Growing Outdoors?

The pot size needs to be considered due to atmospheric evaporation. When a pot holds the correct sized plant, you can water less often. However, when a plant is not big enough, the roots will not seek out the pot, and you will throw away both growing media and nutrient solution because it will vaporize before reaching the plant’s limited number of roots.


Perched Water Tables and Pot Drainage 

Nutrients and water is given to plants at set intervals using a hydroponic timer. As a result, the pot’s drainage needs sufficient time for oxygen to reach the roots. When a pot drains between fill cycles, there will always be a segment at the bottom which remains soaked, this is known as a perched water table.

Something many growers are unfamiliar of, water is not evenly distributed through a growing pot. There are capillary action and adhesion where water is drawn to particles. Because of these two factors, water defies the forces of gravity when draining (matric potential), and these forces intensify the lower you go down the pot.


Smart Pots and Air Pots

Pot size is vital, and aside from losing your hydroponic nutrients from oversized pots, promoting healthy root growth which is the most critical.Plants that don’t scout out the pot or set off root bound will not grow to their full ability.

Smart pots – These pots are made from spongelike fabric that allows the nutrients to flow in and to drain extra water. Water migrates by capillary action from the wetter parts to drier parts, so it is of perched water tables causing problems, and roots have the oxygen they require. Other areas these Smart Pots can benefit is from air-pruning. Roots reach the side of the pot and block, they no longer circle back on themselves and lead to root bound, besides the plant releases new feeder roots, these soak up nutrients faster which leads to larger healthier plants. If there is a downside, it could be larger plants that might need additional support.

Air pots – These pots are plastic, and their key goal is air-pruning. The sides are constructed in a cone-shaped style in which strengthens roots to seek out the pot. Once they hit the side, they are air-pruned, and then new feeder roots are sprouted by the plant. Air Pots build on the features of Smart Pots and can intensify yields by outstanding quantities. If there were a downside, it would be highly efficient draining the pots have, so you may find you need to water more often than usual. Granting the fact that these pots can drastically improve your plants, the same criteria of pot size should be followed, but with the efficient air-pruning, slightly smaller pot sizes can be used to no detriment of your plant’s protection. 

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