I did not give much importance to the container size for my basil as on my early days I used any available pot. However, I wondered whether the container size can affect, in the long run, the growth of the basil. So I did a bit of research on the topic.
The best container or pot size for a basil plant is at least 2 gallons (9 liters) in volume and at 8-10” wide. These are good guidelines for what well-developed potted basil might need to thrive.
A great planter, that fits well indoors due to its clean design and colors, is this one on Amazon (with self-watering capabilities).
Why The Size of the Container Matters For A Basil Plant?
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If you plan to have tall and prosperous basil able to produce all the leaves you might need for your favourite pesto you definitely need a large 2 gallons container with sufficient depth. Indeed, basil, like a few other herbs, has the tendency to grow their roots way more vertically than horizontally, typically up to 8 inches (20cm), although 10 inches deep for your container are recommended.
Such depth is a way that basil has to protect itself. Indeed, in the case of dry weather, the plant can use the water and nutrients in the deeper soil layers. Indeed, this particularly applies to basil as it is a herb that thrives in warmer seasons (spring) where precipitations are typically less common.
This, in turn, explains what might happen if you keep your basil in a small pot for a long time. A small pot implies less space for the roots to spread out and so a lower probability of absorbing nutrients. A lower amount of nutrients will then ultimately prevent the basil to reach its full growth potential. Indeed, longer roots are correlated to healthier basil.
In addition, the plant will be more sensitive to underwatering. Indeed, in a small container, the roots are “squeezed” in small volume making them able to dry quicker the soil. This, in turn, obliges you to water the basil more often (up to once a day) complicating the attempt to grow this plant as it might die quickly if for any reason (for instance going for a quick vacation) you cannot water it.
An aspect of secondary importance is the width of the container. Indeed the most commonly planted basil (also called Genovese, yes like the pesto) grows mainly in high than in width. Hence, when buying a container, pay attention to depth (around 10 inches) and volume (2 gallons or more).
However, if your basil is at its early stages of development and then its roots are not long enough, you can still use a small container that you might have found at the moment in your house.
Nonetheless, how to know when it is time to move your basil to a larger container?
Finally, once chosen the container, your basil needs a good potting mix. Basil indeed, is a bit of a “fragile” herb that would be easily stunted if its roots do not find the right environment (minerals, and proper aeration).
I usually go for the Foxfarm. It is quite good quality. For more, you can also check the article on best potting mix.
When To Pot Your Basil To A Larger Container?
When you grow basil you typically start with a small starter container. However, you know now that at some point, if you are serious in growing your basil, you need to move it to a larger container. However, when does this happen?
There is not a unique and precise answer, although this transition moment is correlated with the size of the plant and of course the size of the original container. In general, I move the basil to its final container when it reaches around 6 inches in height (15 cm). This is, of course, a rule of thumb and not a must-do.
A tip that I use to check if it is the right moment is a visual inspection on how “squeezed” the roots are in the pot. More precisely, with lots of care, I remove the plant from the container (when the soil is a bit dry). The soil will come out with the plant and stay compact (because of the roots). If you notice that the soil volume is densely packed with roots then this is the moment to move your plant.
Another sign is given by the presence of roots out of the drainage holes at the bottom of the container. They definitely crying for more space.
However, a large container might not always good news for your basil.
Can a Container Be Too Large For Your Basil?
Indeed a container can be too large for your plant. This is quite counterintuitive as you might think that larger space will allow the roots to grow even deeper and give a healthier plant. However, this is not the case.
Indeed, healthy basil needs to be able to maintain a normal humidity level of the soil in which is planted. When you move your basil (and its compost) to a very large container (well above the 2 gallons and 8 inches of depth) with new humid compost, the roots might rot.
More precisely, the just planted basil does not have the size to “suck” all the water from the new compost that, hence, will stay wet for a long time. This will cause the roots to rot. This phenomenon is known as overpoterring. This affects any indoor plants as in open ground draining works more effectively.
The presence of extra water/moisture in the soil that the plant cannot dry might also create the right environment for mold growth, negatively affecting the health of your basil.
How Many Basil Seeds In Your Container?
In case you start directly from the seeds (another option is to buy one of the supermarket plants for instance) I recommend to have 3 seeds per starter container (such container can be quite small, like the size of a mug). Indeed, it is true that we should have one plant per pot. This will indeed avoid competition for nutrients-light and it provides better ventilation that ultimately promotes healthier growth.
However, not each seed will germinate. That’s why 3 seeds are commonly recommended. In case more than one plant germinate you need to place every single plant in individual containers to avoid the problem I discussed before. Hence, in such a case is best to place the seeds a few centimeters apart so to remove each individual plant easily.
Given that you are going to move the single plants in individual pots, the starter pots size does not matter significantly, even a small one is enough. An idea that you might like is to use as containers your cardboard egg carton. In each egg-shaped cup, I would suggest one seed for easier later removal of the individual plant. In addition, this set up looks pretty cool to show to your friends and family!
Which Material for the Basil Container, Plastic Or Clay?
Once you decide the size for your basil container it is time to proceed to buy one. However, you might wonder which one is the best for you, the plastic or the clay version?
For your plant well being, I would opt for the clay version. This type of container is more beneficial for most plants including basil. Indeed, the soil moisture and air can penetrate the porous wall of the containers allowing the soil to be drier. Plastic, on the other hand, traps such moisture, a situation that can create problems to your basil if you water it often (humidity raises potentially rotting the basil roots).
Clay is sensitive to temperature variation as it can crack in a cold environment. However, this is not generally a problem for indoor use if not for those of you that leaves in very cold places without heating during cold weather (going for holidays).
You need to know that clay acts as insulation keeping a more constant temperature within the soil, definitely helpful for the basil. However, I would not consider this as an advantage as in your house the temperature is expected to be more or less constant.
However, considering a “house life” for your basil (perhaps seated on the counter of your kitchen, in front of a window) a plastic option is way more practical. The container will be lighter and so easy to move around when you need to clean.
Moreover, in case it falls, a plastic container is unlikely to break, differently from a clay one that, in such a case, can be dangerous due to its sharp corners. This might be a danger if you have a medium-size dog or small children that might play with the container. In such a case I recommend placing the container at ground level to avoid any fall.
Should the container for my basil have drainage holes? Basil container should have drainage holes as essential to prevent waterlogged soil and ultimately roots rot;
Where is the best place to place my indoor basil? Considering that the container size is not an issue, any location close to a south-oriented window/source of natural light will be ideal in order to provide plenty of sunlight.