Finding the right container for indoor soil grows.

After four grows and lots of trial and error, I have reached some conclusions regarding container choice.

Container Size: Proper container size is one of the easiest ways to positively impact your grow.
1. If the container is too big or too small it can hurt the plants by leading to watering mistakes and slow root growth.
2. Transplanting once or twice, from smaller containers to bigger, keeps the plants snugly tucked in the best space for that stage of growth. It also saves time and effort by limiting the need to water towards the end of flowering.
3. Total volume is what matters, not the appearance of size. Which brings me to the next section...

Container Shape: Get the largest possible volume for a given square footage.
1. Volume of a cylinder =3.14 x radius squared x height
2. Volume of a square =length x width x height
3. For a given grow space, squares and rectangles are the most efficient choice when considering maximizing soil volume.
4. Squares and rectangles are a particularly great choice is your space has height challenges.

Container Design: Root pruning pots work.
1. This link, here. TLDR... Greater root mass underneath leads to greater plant mass above. Root pruning pots create greater root mass.

Container Sources: Get creative. It doesn't have to be a real pot from a garden shop.

Here is what I have found that works best in my space. The one diy step I take, which isn't a requirement, is to drill some holes in the bottom to add even more root pruning holes.


I use the 1622 for vegging. The volume is 1.5 gallons.


I use the 1273 for flower. Because of the handle openings I can only fill the soil to that point, which is slightly over 5.0 gallons.

Unfortunately I didn't know about the 1626 and the 1628 until after purchasing the weave baskets. These two have a total volume of 5.2 and 9 gallons respectively. The 1626 in particular is nice because it has such a low profile for a 5 gallon container.

The linked article makes me feel better about my 3 gallon Air-Pots.

I'd just like to add that along with volume, container shape matters, some plants like deeper than wide, such as most photo period plants, some like a shallower, wider container, such as autoflowers. This is due to the differing root structure between the different subspecies of cannabis, C.indica /C.sativa shoot deep tap roots, where C.rudaralis puts out a tap root at more of a 45deg and has a wider shallow root system. A shallow container can stunt growth if it stops tap root downward growth, which is why plants stall in growth when grown in small/root bound pots. It's just a generalization. Otherwise, very good info.

Square pots def have more volume, but if you just have a couple plants, round ones let you turn and position them more freely, so that could be an advantage for some.

innerG said:

Square pots def have more volume, but if you just have a couple plants, round ones let you turn and position them more freely, so that could be an advantage for some.

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Good point. Definitely easier to re-position rounds, which is an important consideration depending on someone's access to the plants.

I grow on a table so it is easy to move around the entire perimeter and move containers as needed. I could see squares especially being a challenge with a grow on the floor of a closet or tent.

Related to this idea is the issue of weight. Lifting five to seven gallons or more of wet soil from ground level is hard, maybe even dangerous depending on the health of your back. So again round pots are easier to slide and spin around and can be a better choice depending on the setup.

Yea, it just depends a lot on the grow setup.

If you have bushy plants that extend out past the pots, it's a moot point because the pots will never get that close to each other

I try not to over crowd my light even 6 seems a bit much once I know who's female I'm gonna go with 4 and up the soil volume from 5gal to 7 or 10 gallon to finish 5 gal yield nice when there was 6 but less plants more soil
they are in one gallons right now just got topped a bit so soon

I plan to re pot to larger containers in a couple weeks veg a bit longer then flip
all organic with water and compost tea love the taste of the finished herb sorry for rambling I'm real stoned happy growing all !

Here are what the roots look like using a root-pruning pot. After transplanting from 4 inch pots, this root mass was produced in 8 days. The roots get very thick and also have significant side branching. Notice how the lowest roots stop growing rather then circling the bottom of the pot.

I've finished in 3 or 5 gal and even 40... depending on veg time...

bokedoki said:

I've finished in 3 or 5 gal and even 40... depending on veg time...

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very true 15 gallon with super soil on my herojuana last year was really fun took longer but was amazing medicine and a nice yield

It's like this all the way around the pot. Each of those roots is growing side shoots rather then circling the pot.

SwankyDank said:

It's like this all the way around the pot. Each of those roots is growing side shoots rather then circling the pot.

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Why is that a good thing? I want more root mass, not less. The plant is only going to be alive about 3 months max, so longer term effects of "root circling" are not an issue.

My experience with air pots of all types is that they dry out too quickly. Same goes for unglazed clay pots. Optimum soil moisture levels make for larger yields. Solid wall plastic containers, round or square, best accomplish that goal.

Like any of the variables to consider in the grow room, container choice is only one of many that influence final yields. Like any of these choices, each of us have to decide which ones we want to play with and see how it changes the outcome. After the experiment we then decide what works best in our situation. Research shows that root pruning containers are "better" at doing certain things and "worse" at others. Whether that matters to someone depends on other variables as well. For some growers, their setup and goals for growing don't fit well with root pruning pots.

bluerock said:

Why is that a good thing? I want more root mass, not less.

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In my limited experience root pruning does create more root mass but it's not just about the mass, it's about the type of mass. Air pots create a root ball that has hundreds if not thousands of small roots that fill the entire pot rather then ten or less large roots circling the bottom. This is one of the main reasons why watering can become an issue... the plant has many more roots drinking from throughout the container and there is less growing medium available to retain water.

bluerock said:

The plant is only going to be alive about 3 months max, so longer term effects of "root circling" are not an issue.

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I have started working with air pots because my previous grows using five gallon containers showed me that the plant was only using about 20% of the soil. So while the large container was avoiding issues that arise from root constriction it wasn't very efficient. For a given container size the air pots will use it more efficiently and consequently I can use my flower space more efficiently. With the reduced container footprint more plants will fit in the same space.

I will also add that this isn't just about the root circling issue, it is also about the research. For a given container size, plants grown in root pruning containers produce greater mass of above ground material: leaves, stems, and flowers.

bluerock said:

My experience with air pots of all types is that they dry out too quickly.

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You are exactly right, they do dry out quicker but your "too quickly" might be just fine for me. It depends on the grower and the situation. I have found that bottom watering is a good way to overcome this problem. I use extra-large drain pans and fill it up so that the water rises over the sides of the pot. With the aeration provided by the air pots, over watering is never an issue.

Thanks for the reply, keep growing.

SwankyDank said:

...root pruning does create more root mass but it's not just about the mass, it's about the type of mass. Air pots create a root ball that has hundreds if not thousands of small roots that fill the entire pot rather then ten or less large roots circling the bottom. This is one of the main reasons why watering can become an issue... the plant has many more roots drinking from throughout the container and there is less growing medium available to retain water.

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Disagree. There is considerable evaporative loss on both the fabric type pots and unglazed clay pots. I'm talking about, say, a 1.5 - 2 gallon container with a finished plant height of around 24-30".

SwankyDank said:

I will also add that this isn't just about the root circling issue, it is also about the research. For a given container size, plants grown in root pruning containers produce greater mass of above ground material: leaves, stems, and flowers.

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I must have missed the part about greater mass, pretty sure they merely stated that the plants were healthier over a longer time frame. However, I would agree that if you can frequently water the fabric-type air pot (i.e. several times per lights on cycle), it would likely produce a marginally higher yield. I prefer to water once.

SwankyDank said:

You are exactly right, they do dry out quicker but your "too quickly" might be just fine for me. It depends on the grower and the situation. I have found that bottom watering is a good way to overcome this problem. I use extra-large drain pans and fill it up so that the water rises over the sides of the pot. With the aeration provided by the air pots, over watering is never an issue.

Click to expand...

Whether you water from the bottom or top, evaporative losses on an air pot are going to be greater than solid plastic given equivalent-sized containers and media density.

Also: I tested the fabric-type air pots and unglazed clay pots. They simply don't hold moisture long enough for my application and there was no noticeable yield difference.

I would also note that real pots from a garden shop are purpose-designed and typically are stout enough to avoid unwanted sidewall flex when moving them around.

bluerock: My understanding of what you have written is that you think root pruning is not helpful and may even be detrimental to healthy growth. You would recommend using basic nursery pots or something similar.

No, I think it would be more accurate to say that I think root pruning - so to speak - is of marginal benefit for a plant that is only going to be alive for 3 months, indoors. And that due to the accelerated evaporation factor of the air pots, maintaining appropriate soil moisture levels is more work. Now, if you get big with the air pots, they are much better. However, indoor growing is all about cramming the maximum amount of plants in the minimum amount of space.

I avoid "basic nursery pots" as they are too damned flimsy. Typical grow shops stock stouter containers. They work quite well and are easy to clean.

As to "detrimental"....well, it has been a while since I looked into the details...but nurseries are known to use small containers to "force flower" their ornamental flowers. This applies to other, more relevant, flowers as well. Cervantes discussed the technique in a rockwool book and there may well be an advantage to "root crowding". I always use the smallest container that suits the moisture requirements for a particular size plant.

To expand on that a bit, consider rockwool. Whether slab or block, at the end of the grow you will be surprised to find that the bulk of the root mass is actually outside the rockwool. This is most notable on slabs. It appears that the rockwool primarily acts as a nutrient reservoir in a kind of NFT arrangement. The roots are jam packed in there, too, all of them right on top of another. Same applies somewhat to containers as well. Roots tend to pile up at the bottom of the container because that is where gravity keeps most of the water/nutrient at.