What is the best plant pot size for cannabis?

The size and type of plant pot can have profound influences on the cannabis plant grown in it. As well as influencing the size of the final plant, the grow containers can allow varying levels of root aeration depending on the type of design. In general, larger plant containers can allow bigger root systems which in turn can support larger final cannabis plants. But this assumes that the grow medium delivers the right levels of nutrition and supports rapid growth. In other words, it’s not just about the plant pot size but also about the contents of the plant pot which allow healthy growth both below ground and above it. Grower skill and experience is also a vital part of the mix. Read on for our top tips on the best types of plant pot and the most suitable sizes for your particular grow style.

Cannabis plant pot sizes and types of grow method

The best plant pot size for cannabis depends on the specific grow method being used. If you specialise in growing with the SOG method (Sea Of Green) then you will lean towards small plant pot sizes, perhaps around 5-10 litres. This will allow you to squeeze in plenty of SOG plants into your grow space.

As well as using smaller plant pot sizes, many SOG growers may prefer to use square (rather than round) plant pots to allow maximised efficiency and floor-space utilisation. When growing with small plant pot sizes the grower needs to water/feed regularly since the cannabis roots only have a small quantity of medium to grow in.

That infers more day-to-day maintenance and attention can be required when growing cannabis in smaller plant pot sizes. If you’re able to attend to your plants on a daily basis that won’t be an issue. But if you often enjoy long weekends away, then growing cannabis with small plant pot sizes may bring it’s challenges.

Related:
Growing cannabis with the Sea Of Green method

However some cannabis growers like to grow the largest and most productive plants possible. Such growers would often use 50-100 litre container sizes and may only grow 1-2 plants per square metre. This includes those growing with the SCROG method where heavy harvests are targeted with high yields from each individual plant. When growing photoperiod feminised cannabis seeds long periods of vegetative growth can be used to allow the plant to fully utilise all available root space and reach a large size.

Related:
The cannabis vegetative grows phase, how-to guide

With a large and healthy root zone, combined with a nutritious grow medium and plenty of oxygen around the roots the cannabis plant has all it needs to support a large plant above ground with heavy harvests. Those growing with the SCROG method try to maximise efficient use of their grow light by growing all the blooms equidistantly from the light source. If you’re considering a SCROG grow with large plant container sizes then the following expert SCROG guide is essential reading.

Related:
Growing cannabis with the SCROG method (Screen Of Green)

When growing cannabis in large container sizes (e.g. with a SCROG grow) the need to water/feed on a daily basis is often less critical than when using small plant pot sizes. That’s because large containers, by definition, contain a greater supply of nutrients, minerals and water. If you sometimes go away and leave your plants unattended for a couple of days at a time then it could be convenient for you to consider using large plant containers.

Different types of cannabis plant pots

Traditionally, people grow cannabis in plant pots made from clay or (black) plastic. These are often round or square with holes at the bottom to allow excess water to drain away. These do a good job when cannabis is grown in them. But there are better, more modern, grow containers which offer superior levels of root aeration. Two of the more common ones are airpots and grow sacks.

Airpots, air pruning and superior oxygenation of the root ball

Airpots have become very popular with cannabis growers. Made from dimpled black plastic with lots of air holes, air pots allow oxygen to penetrate the root zone. This allows rapid root growth. Where roots reach an opening in the container side they ‘air prune’, creating more roots which search for moisture and nutrition.

The result is a plant container with excellent root growth. Whether you’re growing autoflowering cannabis seeds or photoperiod feminised seeds airpots are highly recommended and are available in small, medium and large sizes according to your tent size, grow method and style.

Grow Sacks, porous grow bags which are re-usable and affordable

Another family recent innovation in cannabis grow containers has been the emergence of grow sacks. These are available in sizes from around 1 litre to 100+litres. They are made from air-permeable fabrics such as felt or similar tough (but porous) materials. These allow good levels of aeration to the root ball.

Those growing large individual plants (in the natural way or with the SCROG method) often use 50-100 litre grow sacks. When using a good quality soil, perhaps with slow release organic nutrients such as BioTabs, it may not be necessary to add anything other than water throughout the grow. That’s because a large container can hold sufficient nutrients/minerals to support a plant from cannabis seed all the way through to harvest.

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Cannabis plant pot sizes and yield

If you grow identical cuttings (cannabis clones) in different sized plant pots you would see (assuming equivalent grow conditions, nutrients, lights etc) that the largest plants would grow in the largest containers. The actual yield from each different container would depend on the specific genetics, light size etc.

But the general trend would show that the plants with the largest root ball and largest food reserves (i.e. from the largest grow containers) would produce the biggest harvests. This principle can be used by the grower to allow them to optimise the yields that they can produce from their grow tent/grow room.

So one way to increase the size of the plants that you grow could be simply to grow them in larger plant pots. However, that also means that you are likely to be able to get reduced plant numbers in the same area. Indoor growing can be a trade off between growing small numbers of large plants, or higher numbers of smaller plants.

Your own grow preferences and grow method will dictate what works best for you. Just remember to start with the best cannabis seeds and enjoy the grow!