Choosing the size of your pots can seem like a daunting task to gardeners new to container gardening. The space available, size of the plants and temperature of your grow space are three main factors that must be accounted for when selecting your containers.
The size of your grow space is an obvious place to begin. If you are gardening indoors or on a small balcony, you’re probably dealing with a limited space. Height is also a factor. If your grow space is small or short, then shorter, smaller pots are a better choice for your space, but don’t expect to grow large plants in these smaller pots.
This leads to the next important factor to consider when choosing your pots and containers: the size of the plants you intend to grow. Small seedlings and cuttings have simple root structures and need only small containers, about 4 in. in diameter, to grow in. As they grow and the roots become far more complex, you’ll need to transplant to larger containers—between 6 and 12-in. wide—to accommodate the rapidly growing roots.
It is up to you how large the final container is, and your choice will have a direct effect on the size of the plant in it. When container gardening, the above-ground growth is directly affected by the health and size of the roots, and the larger the container, the higher the potential for growth and yields.
This rule is only true with container gardening, and there are many other factors beyond container size. If you want to go for fewer, larger plants, then large containers are ideal. If you want to grow a larger number of small plants and have quicker crop turnovers, then using smaller containers is the way to go. Smaller plants also take up less water and nutrients than large plants, which means you can use smaller containers.
The temperature of your grow space is another important variable to consider when selecting the final size of your containers. Plants growing in warm spaces, such as under HID bulbs or outside in direct sun, will need more water to replace the fluids evaporating from the heat, so they will require larger containers to give them enough water and nutrients throughout the day.
If you have a warm grow space and want to grow in smaller containers, you will need to use a drip irrigation system to periodically pump water from a reservoir to your plants. Otherwise, they will dry out.
For cooler grow spaces, the opposite is true when it comes to container sizes. If the containers are too big, the soil will stay too moist, adversely affecting plants. If plants become waterlogged, the roots will suffocate.
Overly wet, cool grow mixes can invite pests, algae and destructive fungi into the garden. If your mix is very wet for more than 3-5 days, your room is too cool, or the containers you are growing in are too large.