How Big Do Autoflowers Get? Choosing the Right Pot Size

How big an autoflower gets depends mostly on its genetics, its light and how much room its roots have. Pot size is the part you control most easily. Our own preference is a big pot, as far as your space allows, and we think potting up from small to bigger as the plant grows is important.

Why pot size matters for autoflowers

Roots need room. When they hit the walls of a small pot early, the plant slows down, and an autoflower has little time to make up for it because it starts flowering on its own schedule, whatever size it has reached.

This isn't just a cannabis thing. A large review of plant studies found that, on average, doubling the pot size gave plants about 43% more biomass (Poorter et al., Functional Plant Biology 2012). That review covered many plant species, not cannabis specifically, so take it as a general pattern rather than a promise for your plant.

A bigger pot isn't free, though. It takes more soil, more room in your tent or on your balcony, and it stays wet longer, which makes overwatering easier.

Our advice: go big, but pot up step by step

If we were growing an autoflower ourselves, we'd go for a large pot. The limit is your setup: the height and floor space of your tent, how many plants you want to fit, and whether you can still lift and move the pot when it's full of wet soil.

We also move plants from small to bigger pots as they grow. A lot of guides tell you never to transplant an autoflower and to sow straight into the final pot. We see it differently: we think potting up from small to bigger is important, as long as you do it carefully.

What "carefully" means in practice:

• Pot up when the roots have filled the small pot but before they start circling the bottom.
• Water the plant a little beforehand so the root ball holds together, then lift it out in one piece.
• Put it in at the same depth, fill around it, and water it in.

In the end, your own experience counts too. If you've always had good results sowing directly into the final pot, there's no reason to change what works for you.

Pot sizes in litres and gallons

Pots are sold in both litres and US gallons, which causes confusion. One US gallon is about 3.8 litres, so:

• 2 gallons is about 7.6 litres
• 3 gallons is about 11.4 litres
• 5 gallons is about 18.9 litres
• 7 gallons is about 26.5 litres

Smaller pots let you fit more plants into the same space. If you grow just a few plants and have the room, a larger pot gives each plant more to work with. Which size suits you best depends on your space, your plant count and the strain, so treat these numbers as a reference, not a rule.

Fabric, plastic, terracotta or air pots

Fabric pots

Fabric drains easily and lets air reach the roots. Check how wet the soil is regularly, especially in warm weather. Outdoors, keeping pots out of the hottest afternoon sun helps; our post on shade for cannabis plants covers that.

Plastic pots

Cheap, light and easy to find. Make sure there are enough drainage holes, because plastic holds water longer than fabric.

Terracotta pots

Clay pots breathe a little and are heavy, which keeps tall plants stable. They are also fragile and hard to move, so they fit a fixed spot better than a tent you rearrange often.

Air pots

Rigid pots with holes in the sides, so air reaches the roots like it does in fabric, while the pot keeps its shape.

Whatever pot you choose

• Drainage: water must be able to run out freely. Standing water around the roots leads to rot.
• Soil: autoflowers like a light, airy mix. Our post on the best soil for autoflowers goes into detail.
• Clean pots: wash reused pots before you start, so you don't carry problems from the last grow into the next.
• Stability: a tall plant in a light pot tips over easily. Use a heavier pot or a stake.

Growing outside or on a budget? Our guide to growing at home without special equipment shows what you can do with simple containers.

Choosing seeds for your space

The final size of an autoflower is set largely by its genetics, so the strain matters as much as the pot. Browse our autoflower seeds to compare strains, or look at our feminized seeds if you have the time and space for a photoperiod plant.

Questions people ask about autoflower pot size

Can you transplant autoflowers?

Yes. Many guides say you shouldn't, but we pot ours up from small to larger pots. Do it once the roots fill the small pot and keep the root ball intact.

Is a bigger pot always better?

More root space generally means a bigger plant, but only if your space, light and watering keep up. A huge pot that stays soaking wet does more harm than good.

What size pot do I need for a small tent?

Measure your floor space and height first, then decide how many plants you want. Fewer plants in bigger pots or more plants in smaller pots can both work; it comes down to your setup and the autoflower strain you pick.