The best pot size for autoflowers


Ensuring that your autoflowers have a reliable and safe container is an important, but often overlooked task. The type of container you choose, its material, and size all have a significant impact on the way your plant will grow. And while regular cannabis seeds come with clear guidelines on the correct size of containers, things are a bit trickier when it comes to autoflowers. The two factors you need to consider are the eventual size of the plant, and the time it will take to reach harvest.

Pot size for autoflowers

Perhaps the most important thing when choosing containers for your cannabis is size. Most growers buy autoflowering seeds because they don’t have a lot of growing space, and they don’t want enormous plants that can reach more than six feet in height. The pot size can have a major impact on the eventual height of the plant. If you choose a small container for your autoflower seed, then it will remain short as it will quickly become root bound and the resulting stress will slow the growth of the plant.

One of the many advantages of autoflowers is the fact that they are generally small in stature and are unlikely to exceed 18 inches in height. Most modern varieties are also quick to reach harvest in as little as eight weeks. Eight to ten weeks from seed germination to harvest is the typical lifespan of autoflowers.

If you buy your marijuana seeds from a reputable seller such as Weedseedsexpress and you know the provenance of your chosen variety, it becomes possible to work out the ideal container size for the plants.

So what is the best pot size for autoflowers? 

1.5 to 2.5 gallons is optimal for eight-week autoflowering plants. The container size is important – too small, and it will have a negative impact on your yield, too large, and you will waste soil unless you have the space to cope with a large-growing plant.

Trial and error

As autoflowers should not be re-potted, a container that is between 1.5 and 3 gallons should be fine. It is worth experimenting with different plant sizes to see what works best for your chosen variety. If you need your plants to remain compact, choose smaller containers; but larger pots are generally best if you want lots of vertical growth with plenty of side branches.


We do not recommend re-potting for autoflowers as it will cause plants to experience a temporary shock and slow their growth. Simply plant your seedling from its growing cube into its final pot or sow directly into the pot itself. With photoperiod plants, it is best to re-pot just a few times so that you don’t cause excessive damage or prolong the growth phase too much.

Different types of containers

Next, let’s look at the different types of plant containers that are available. Any of these are fine for autoflowers. It is essential to consider the material the pot is made of – such as plastic, clay, wood, metal and even coconut fiber. Keep in mind, however, that no one container material is “best” as each has its advantages and disadvantages.

Clay pots, for example, will remove moisture from your soil, which is why you need to water more frequently. Metal containers can rust, store too much heat and even cause contamination. Wooden containers are excellent for growing weed, but they are often very large and expensive. The most common choice are plastic pots. These are inexpensive, durable, and clean. They’re nothing special, but they’ll do the job and do it well.

Plastic tubs

You can get plastic pots for little money pretty much anywhere. They are durable, waterproof and available in a range of sizes and styles.

Fabric containers

Fabric pots, also known as “Smart Pots”, are plant containers made from vegetable matter, usually coconut coir. When the roots reach the sides of the pot, they become trapped in the porous fabric and naturally trimmed by the outside air. This “air pruning” even encourages root growth and prevents ring roots (that is, they do not outgrow their pots). Another advantage of fabric pots is that their porous structure makes it almost impossible to overwater your plants. These are inexpensive, and you can easily poke holes in them. They are available in many sizes and colors. However, they are not very robust and can split, and they do not protect roots from extreme temperatures.

The main disadvantage of fabric pots is that they dry out faster than ordinary pots. You will need to water them more often or use larger pots with more soil to keep this from happening. Fabric pots are also less robust than standard planters. Since they are more like bags, they are more likely to tip over.

Terracotta pots

Traditional clay pots promote a healthy root system, and roots have better access to air and oxygen. It is also much harder to overwater. However, the pots tend to dry out quickly, and they can easily tip over.

If you get these classic flower pots, you should ideally get them together with a matching saucer. The trivet catches the water that runs off under the pot.

Terracotta and plastic pots must have drainage holes in the bottom to avoid waterlogging. Not all pots have holes; sometimes, you will have to pierce them yourself before growing your plants. This is much easier if you are working with plastic, and it is not necessary with fabric pots. Save yourself the hassle of breaking your containers by buying clay pots with pre-made holes.

Terracotta or clay planters are more cumbersome than plastic pots, but they can be good choices because terracotta can absorb and retain excess moisture. This provides a cooling effect that will benefit the roots of your plant in the hot summer months. Small disadvantage: you could have to water more often.

Air Pots

Air pots, also known as root trainers, are similar to smart pots. By air pruning the roots, air pots prevent ring roots while also promoting optimal growth. The difference is that air pots are made of plastic with perforated side walls instead of some type of fabric. They are more expensive than other options.

While they will significantly benefit the growth of your cannabis plants in the aforementioned ways, air pots have the same disadvantages as fabric pots. You will have to water more often, as water seeping through the sides can dry out the soil faster. However, they are more stable than fabric pots. Note: If you are growing indoors, you may want to place air pots on large trivets to collect drainage water.

Round or rectangular?

When growing weed indoors, you may want to opt for rectangular pots rather than the normal round ones. Although the latter are absolutely fine, rectangular pots allow you to make better use of your available growing space. Some rectangular planters for growing cannabis are particularly deep. These are well suited to maximize the growth of individual specimens as the roots can penetrate deeply, and the plants will thrive.

Another consideration when growing outdoors is to opt for white pots, as they store less heat than black or gray containers.

Tips for growing autoflowers in pots

Regardless of the variety, you choose, here are some final tips how to grow autoflowers in pots:

Separate the plants

Ideally, you’ll want to use one container for each plant. This avoids competition among the root systems and allows you to take care of each plant individually. One plant per pot will also make re-potting easier later. If the soil in a pot is contaminated, over-watered / over-fertilized, infested with pests, etc., the rest of your plants will not suffer if each plant is given its own pot.

Make sure there is enough drainage

Unless you know your cannabis very well and can accurately estimate how much water each plant will need, it is best to buy a container with holes/perforations in the bottom. In fact, you should still make your life easier and opt for holes, even if you know exactly how much they need. This allows excess water to drain and oxygen to flow through the growing medium, reducing the chance of root rot – a problem that occurs if the soil is left too wet for too long. Don’t over water – stick your little finger an inch into the soil to see how moist it is before watering.

Invest in matching saucers for your containers

By placing your containers on saucers, you can catch the drain and ensure that your plants do not get wet. Choose a trivet that is large enough to catch any drainage coming out of the bottom and possibly the sides of your pots. You can even place a large bowl under several pots to make your work easier. Just make sure to empty the coasters regularly!