When growing cannabis, light intensity, temperature, humidity, nutrients and carbon dioxide are essential, but did you know that the pots you use also play a massive role? There are many varieties of pots on the market, but knowing which ones are best suited for producing the best root mass, so in this article, I will explain the different types of pots available to a grower, which pots should be used for the various stages of plant growth, as well as the impact of the material and environmental conditions.
Overview of pot types for cannabis cultivation
I remember when I first started growing cannabis, the only pots I really knew about were cheap plastic pots. However, there are actually six different pots that can be used, with each having its own pros and cons. Below is a breakdown and explanation of each pot to help me decide which pots may be most practical for your next grow.
Plastic pots
Plastic pots will be available in either a round or square shape, and can be bought from a local garden centre or your local grow shop. They will range in size from small nursery pots for starting seedlings, all the way up to 50 litres.
The pros:
- They are cheap to buy
- Easy to source locally or online
- Available in small to large sizes
- Can be cleaned and reused
The cons:
- Plants can become root-bound
- Some pots degrade over time
- Large pots can be expensive
- Outdoors, plastic pots can become hot in the sun
Terracotta (clay) pots
Clay pots are solid pots that work great for house plants and add character to an outdoor garden space. You will usually find clay pots in a garden centre, and they have an aesthetically pleasing finish.
The pros:
- They are solid and thick
- Look great in the garden
- Can be coloured and decorated
The cons:
- There are usually no holes at the base
- Large pots can be weighty
- Can break and crack
Fabric (smart) pots
Fabric pots are typically made from a felt material, making them thin but firm. These pots are available in different sizes and will usually be the most expensive pots compared to plastic pots.
The pros:
- They are lightweight and can be folded.
- Allow air to pass through the fabric
- Can insulate the roots during colder months
- Promote root pruning resulting in a large root mass
- It can be washed and reused.
- Prevent roots from becoming root-bound
The cons:
- It may be expensive compared to other pots
- The soil may dry out faster
- You may need to water them more often
Air pots
Air pots are designed to be rolled up and connected to form their round shape, with a plastic base that needs to be connected. They have a very distinctive look and oftentimes can confuse a beginner grower when on display at the grow shop.
The pros:
- They are oxygen-rich pots
- Produce a prolific root mass
- Easy to assemble together
The cons:
- The cost is relatively high
- Water can pour out the sides
- You cannot bottom-feed using air pots
Hempy buckets
Hempy buckets can be used for hydroponic-style grows using perlite. They work by placing a hole 1-2 inches from the base to allow water to pour out, creating a reservoir at the base of the pots that can be replaced with fresh water or nutrient solution.
The pros:
- You can use any plastic pot
- Only need to make a centimetre-sized hole
- Uses an inert medium such as perlite
- Cheap and easy to set up
The cons:
- The reservoir needs to be changed frequently
- The water inside can become stagnant quickly
- Does not allow much oxygen inside
- Liquid nutrients are required for food
Grow bags
Grow bags are basically plastic bags with a pre-made hole in the base. The bags are filled with soil or coco coir. They are available in various sizes, making them suitable for large quantities at a low price.
The pros:
- They do not take up much space when flat
- They are cheap and available in large quantities
- Ideal for growers with an ample grow space and a limited budget
The cons:
- They do not have a solid structure when full
- The bags are thin and can rip or tear easily
- It is not easy to repot plants grown inside.
- They don’t let much air into the pot.
Trays and saucers for water run off
One way to keep the grow room floor dry after watering is to use a tray or saucer underneath the pots. The excess runoff water that exits the base of the pots will be collected into the tray and wicked back up into the growing medium later on.
Saucers and trays enable growers to water plants from the bottom and provide a convenient way to check pH or EC levels in the runoff water. Using saucers prevents the grow room floor from forming small puddles underneath the pots and potential flooding risks.
Pot size matters – matching capacity to plant growth stage
Cannabis plants will go through different stages of growth during their life cycle, and have different requirements and needs as far as light intensity, root mass and nutrient uptake are concerned. Below is a breakdown of the various pots that you want to consider using during each stage and why.
Pot sizes for seedling stage (1–7 L)
The cannabis seedling stage, which lasts 2 weeks, is when your delicate seeds form their first sets of leaves and establish a firm tap root and fibrous roots. At this stage, seedlings do not require much light intensity or nutrients as they begin to develop. Using pots that are 1-7 litres in size will be ideal for this stage, with the intention of repotting after 14 days into a larger pot.
Pot sizes for vegetative stage (approx. 7.5–25 L)
Once your seeds are over 14 days old, they are now ready to begin the vegetation stage and produce fan leaves, side branches and internodal growth. The vegetative stage indoors can last as long as the light cycle remains on 18/6. In this case, using a pot between 7.5 and 25 litres in size gives a grower plenty of flexibility to grow plants as big as they need and fill out the pot with roots.
How pot size affects root binding, watering frequency, and nutrient uptake
One thing that cannabis plant roots love is oxygen, and the more oxygen present, the faster they dry out between waterings, and the more they can prune themselves, resulting in a far greater root mass and structure.
Felt pots and air pots are popular amongst growers for providing a high oxygen environment for cannabis plants, which is why they are associated with a higher frequency of watering and bigger yields compared to plastic pots or grow bags.
If a plant becomes too big for its pot, its roots will become root-bound, meaning they have run out of space to grow, resulting in a cessation of growth and nutrient uptake. You should always transplant a root-bound plant into a larger pot with fresh soil or growing medium to avoid root-bound characteristics and keep nutrient availability optimal.
Material and environmental considerations
The material that your pots are made from and the environmental conditions can play a significant role in root health and development. Below is an explanation of how indoor and outdoor growing conditions play a factor, regulating temperature, as well as weight, durability and handling practicality.
Indoor vs outdoor growing
As an indoor grower, you can control the temperature and humidity of your grow room. This means that you can also influence how hot or cold your pots become. Outdoors, the weather will dictate the temperature of your pots, especially when the sun heats up black plastic pots and grow bags, or colder nighttime temperatures.
Temperature regulation
The roots of a cannabis plant thrive when the growing medium is warm and oxygen-rich between 20 and 30 degrees Celsius. When the temperatures are too warm (above 30 degrees Celsius), root health can be quickly affected, which can promote potential root disease and pathogens. When the pots become too cold (below 20 degrees Celsius), the root and plant growth and development can slow down, resulting in a smaller root mass that affects nutrient uptake.
Weight, durability, and handling
A good pot can stand the test of time, enduring many back-to-back harvests. It's easy to lift between waterings, move around if necessary, and handle and carry with ease. Fabric pots and air pots will be the best candidates in this scenario, in comparison to clay or thin grow bags.
FAQ’s
How many times should you repot a cannabis plant?
I would recommend that the optimal number of times to report your cannabis plants would be 2-3 times in total, depending on how big you want your plants to be once they flower. It is best to transplant into the final pot several weeks before flowering is induced to avoid stress.
What is overpotting?
This occurs when you repot your cannabis plant more than required, primarily as you draw closer to inducing flowering. You should repot your plants after the seedling stage and during the vegetation stage, settling them into a larger final pot. Avoid disturbing the plants once they are transitioning or producing buds.
Can autos be repotted?
Yes, you can repot an autoflowering cannabis plant; however, it is not advised, as doing so can cause the plants to become stunted and slow down growth. We recommend planting your autos directly into a large-sized pot (25-30 litres) for the best results.
