Using fresh basil leaves directly from your plants not only make your dishes tastier but also will develop your green thumb. I grew basil indoor for years and it is not among the easiest herbs. It requires attention to a few details. Once you know them you are sorted.
To grow basil indoors it is important to replicate the basil natural environment and provide adequate amounts of 1) (root) air, 2) water 3) nutrients, and 4) light. The first three elements deeply interact with the soil where the basil is potted. At least 6 hours of sunlight are required.
Hence, what does that mean for you, and what do you actually need to do to have some large and juicy basil leaves growing on a pot on your windowsill?
First I will discuss with you the elements you need for your basil (soil, fertilizer, light, etc…). Then, when the do list is understood, I will go through a practical step-by-step guide to grow basil indoors. Enjoy!
Growing basil successfully requires balancing out four elements: 1) air, 2) water, 3) nutrients, and 4) light. This is what I called the plant square.
Of the four elements that basil requires to grow, light is the only one that is not related to the soil.
Air, water, and nutrients interact deeply with the soil (or any growing medium) the basil is potted too. This is paramount for you to understand.
There is not such a thing as the perfect amount of water or the perfect amount of nutrients. It all depends on the soil where the basil is potted in.
A very draining soil (sand-rich) will oblige you to water your basil daily and provide nutrients externally (as the soil is very poor on it). This not the case with compost that, on the opposite, might cause your basil to “drown” very easily if you water as frequently as you would in normal potting soil.
Hence, the question you need to ask is not how to grow basil. Rather how can you grow easily and with little care grow basil?
The best soil to grow basil needs to be well aerated with medium drainage capabilities. It should have a neutral pH and a medium level of organic matter and nutrients.
Hence, what good soil for basil should have?
Basil will not grow in compacted and high water retention soil such as clay, silt, or even pure compost. Touch the soil after it is dry. Is the soil compact heavy? Do you see any irregularity on the surface through which the air can flow and reach the roots?
If the answer to the previous question is no, then your soil is very likely compact.
Does your soil stay wet for days after watering? You are either watering too much or your soil is too water absorbing. Check the label of your potting soil bag. Does it contain coco coir, peat moss, or compost? If so perhaps their percentage is too high and you might need to balance with perlite or other larger gritty material. Basil is easily prone to root rot caused by lack of oxygen-induced by excessive watering.
Basil will not grow (if not with big effort) in very draining soil such as sand. Such a growing medium does not have enough water retention capability and the water will zip through the basil roots not allowing it to drink.
My best pick for growing basil is the soil below, it is sold at a decent price. I do recommend also a third of perlite in volume to increase the aeration and drainage.
If you want to know all the secrets on basil potting soil check the full guide below.
A planter is just a planter, right? Not exactly.
Any herb, basil included, develops roots that, in turn, capture nutrients and water “trapped” into the soil that is then provided to the whole plant. Here you can start understanding the impact of the planter size.
A too-small planter (less than 2 gallons) will lead to a stunt basil growth as the basil will not have enough volume of soil from which to extract its nutrients. A planter from 10 to 14 inches in diameter is ideal to allow full development of a single mature basil plant.
The one below is a quite good quality planter.
Do you want to know more about size and material? Check the guide below.
Never place rocks or pebbles at the bottom of the planter. The idea to place a rock at the bottom of planters as a way to increase drainage is a fake myth that is more likely to damage your basil than benefit it. You do not believe me? Check the article below with all the details.
A planter needs to have drainage holes at the bottom, ideally at least 3 distributed over the bottom. The lack of them will certainly cause the plant to die for excess moisture and root rot.
You have the potting mix and planter ready. You need now to water your basil plant. What to do? How much water?
Considering the planter and the potting mix suggested (perlite included) a fully grown basil plant needs to be watered once, maximum twice a week, and gradually less when approaching autumn.
However, to give you this number I was thinking a lot. It is a fair rule of thumb and you will be ok with it. However, how can you water basil even more effectively?
Do you want to learn more about how to water basil? Check the detailed article below for even more tricks!
Basil is a plant that requires a medium level of nutrients. Indeed, different from plants meant to produce large fruit (such as squash and melon), basil just produces leaves and so it is not a heavy feeder.
Indoor basil plants thrive best with a 10-10-10 NPK ratio fertilizer provided every 1-2 weeks during the spring until late summer. Liquid fertilizer for potted basil is an ideal option.
In case If not a 10-10-10 is available, anything organic with an N-P-K ratio below 10 is ideal. Why? Because using a “strong” fertilizer (any fertilizer where one of the NPK nutrients is above 10) can damage the plant especially if in the hands of beginners that might tend to provide too many nutrients (causing serious damage to the plant and the soil).
My suggestion, considering what is available online, is the one below.
If not available, another good fertilizer for a basil plant is the one below (less strong as organic). For this one, once you read the instruction, you will probably need to use a larger amount compared to the previous one.
Quite often I witnessed friends stunting basil plants for too much love due to excessive fertilizer. Fertilizers build salt into the soil that at the same point will kill the plant.
If you want to know more regarding how to fertilize herbs and the risk of overfertilization check the guides below.
Any plant, basil included, can thrive indoors only if the gardener can recreate inside its house the same conditions in which the plant thrives outdoors.
Basil is a Mediterranean herb, a native of the tropical region of Southeast Asia, and very well know to grow also in warm countries such as Italy and France naturally. It is indeed called a “Mediterranean” herb.
If you are not in Italy right now (a beautiful country by the way) do not disappear.
What basil needs to thrive is just sunlight for at least six hours a day, ideally eight hours. This is a relatively easy condition to meet in many areas of the planet, especially in spring-summer (northern hemisphere) and winter-autumn (in the southern hemisphere).
What if you cannot guarantee such long light exposure?
Well in this case you are either trying to grow basil out of the sunniest season (like winter or autumn if you live in the USA or UK) or your available window sills are north-faced.
In this case, your basil plant can still grow but slowly and very likely not to its full potential. The danger is that it will stop altogether and be in a “stunt” state for a long time.
If you are a beginner, I would avoid altogether growing basil in such conditions. Why? It will be harder and, as stated before, it will require more “active” effort from your side. However, it still possible.
Actually, it is possible to grow basil even inside a room with no windows.
How? Providing the missing light with grow light lamps
No plant can differentiate the light provided by the sun and an “equal” light (yes, this can be reproduced artificially) provided by a lamp. However, you need to be careful. Here I am using the word “equal”. This means that the light on the ceiling of your bathroom is producing a light (probably whitish) that is not equal to sunlight, and so not very useful to grow basil.
What you need is a bulb that produces the same type of light that the sun produces. This is not difficult at all nowadays. There are plenty of lamps specialized for that. These lamps often appear purple and they are called grow light.
Yes, I know, sunlight is not purple. Without getting into much detail a grow light is given by different color components. The ones that a basil plant (as well as the majority of plants) use to grow are blue and purple. This is a very simplified explanation and for more details, if you are curious, check the grow light guide below.
Hence, if you provide the missing light with a grow light lamp you are fine. Your basil will grow as if it was outdoor. I would avoid using light 24/7. Eight hours a day (minus the hours of natural light your basil receives from your windows) will do the job.
If you are starting out, a good quality-price compromise is the grow light below, it is small, flexible, and cheap. You might need some support to place below the lamp (books, bricks, whatever you have at hand) to make the lamp standing above (from the side is fine) of your potted plant.
Basil, different from many hardy herbs, is quite sensitive to the ambient temperature. If this drops below 41F (5C) the basil will start suffering to then die in case of frost (temperature overnight close or below 32F (0C).
This way is almost impossible to grow basil outdoors in autumn or winter. This applies only if you live in a very temperate region (Canary island, if so lucky you!) or close to the equator.
However, growing basil indoor has the benefit of not encountering this problem.
Indeed, even during cold winters and when your heating system is at the minimum or switched off, your house has a normal level of insulation that should not be a problem as it will never experience frost.
However, if you really want to promote massive growth the ideal temperature is 25C, this is based on extensive research performed by the University of Nottingham by measuring dry mass (weight of leaves) and oil content (the more the better) of basil plants grown at different temperatures.
A difference of only 10degress (from 25C to 15C) can cause a drop of a third of the oil content in the basil leaves.
Plants grown at 25°C for 2 weeks were taller and had a higher dry matter content and larger leaves than plants grown at other temperatures – Source
The previous sections were focused on the single element you need to have in check to grow the largest and healthiest basil plant: soil, planter, watering, fertilizer, light, and temperature.
It might sound like lots of stuff and believe me, you can grow healthy basil without all this information. However, if you want to have a bush, then this can be worth reading.
Here I will guide you by hand in the process of growing and maintaining basil plants, from start to finish by putting together what we learned so far.
This is the “easy” approach. Indeed, we are not going to start from seeds, but straight away with a baby plant that you can grow even more!
Let’s go quickly what all the material you need
There are many things you can replace or manage to have for free when growing a basil plant. The only thing I would spend a few dollars on is on soil, no questions on it.
As you learned before through soil the basil absorbs water and exchanges gases through its root respiration and also traps nutrients.
My suggestion is the Foxfarm with a third of perlite. I use the brand below and they have worked well so far.
If those are not available to you another potting soil should be fine. It is important to avoid those that advertise “save water” in watering or those that have water-retentive material (such as vermiculite). Those are hard to go with as they retain too much water at once increasing drastically the chance to kill basil. Those soil are good for vegetables and highly demanding crops.
An 11+ inches diameter planter with drainage holes will suffice. Either clay or plastic pot will be fine. I sometimes use old cleaned plastic painting containers and drill the holes at the bottom.
In Amazon, there are several cheap and less cheap options. Here one of them.
Growing from seeds is exciting, but definitely not for first-time gardeners. Considering that basil is a short-lived herb (it is an annual herb that lasts at most around 10-11 months) you might not want to wait a month to start harvesting some leaves.
Here my trick
- Go to any grocery store;
- Take either one of those plastic bags where they sell basil leaves for condiments or a small living plant. Be careful, should be fresh basil leaves, not dry;
- If you go for the basil leaves check through the bag (it is usually transparent) that the leaves come with a few inches stem. The stem with the leaves should have at least two pairs of leaves or be a few inches long. If there are only leaves with no stem then do not buy as the leaves only will not develop into a plant;
Here you have your plant
In case you bought the basil leaves with the stem only you need 1 to 2 weeks to allow your plants to grow some roots.
What to do?
To grow basil roots from a basil stem leave 2-3 pairs of leaves at the top of the basil stem. The stem should be then placed in a water glass until one node on the stem (a node is where the leaves were) is below the water level.
This stem will develop wonderful white and thin water roots. Check the full guide below on how to save a supermarket basil plant.
Once the water roots are there you are ready for transplanting
If you bought the plant from the supermarket you do not need it. It is an already fully grown plant.
Tip: for a supermarket plant I would suggest cutting one-third of 2-3 stems and try to develop some roots in water. This is because this will give you higher chances to grow the basil as rather than one (actually many small plants) you can have a few more.
Check the guide below for more on how to save a basil plant from the supermarket
Now, the final and best of all the steps. Finally placing your basil plant with its roots on the soil.
Here what to do
- Place the at the bottom of the planter the potting soil
- Add a third of perlite and mix the two vigorously
- Fill the pot at ¾ of its volume
- Make a hole at the center with your hands
- Place either the supermarket plant or the stems with the white roots (around 2-3 inch long)
- Cover the remaining part of the planter with soil. No need to add perlite here as the roots will not likely extend in this area and you will avoid having perlite floating on top of the soil
Place the potted basil in the sunniest spot in your house. Basil leaves are rather gentle, so they can suffer from sunburn (black spot on basil for more info). Hence, if you live in a very sunny area with a south-facing window place the basil a few inches away from the window.
Because in this way it will avoid long hours of direct sun but it will still receive tons of good, almost direct sunlight, intense enough to promote growth.
If the light is an issue, then you can go for a grow light as the one suggested for instance. Six to eight hours of artificial light are more than enough.
How to water a potted basil plant?
In the beginning, while learning how to water the basil plant, wait until the plant starts wilting. When knowing the regularity by which this happens, start watering 1-2 days before that to avoid excessively stressing the basil plant.
When the water starts dripping from the drainage holes it is time to stop. In theory, and with a bit of practice, you start to stop watering a bit before that, especially if the plant is small. Indeed, each soil has a water retention capability. This is the amount of water teh soil can absorb and it is saturated, essentially cannot hold more water.
Overwatering a basil plant is even worse than underwatering, so be careful and, if indeed just wait a few days.
If you want to go for the harder (and likely more fun way!) then just go to buy some basil seeds and you are ready to go.
Here what you can do to germinate basil seeds
- Place some of the potting soil mentioned before (no perlite) in a plastic cup – make one hole at the center (even a crack is fine, just to let the water ran away in case you exaggerate with it)
- Water the soil thoroughly
- Place 3 seeds at the center
- Add a thin layer of soil (I would say half an inch) on top of the soil
- If the area in which you leave them is cold, put a transparent plastic cover on top (the same used for freezing food bag for instance)
After 2 weeks you should have a small basil plant ready to be transplanted following exactly step 2 and 3 in the previous step by step for beginners.
Below if you want to germinate other seeds you can find my full detailed guide
This is something that is misunderstood by many, but not by you if you are reading this.
Pruning is a practice that promotes health and growth in herbs, basil included. The most important thing is to be able to prune at the right spot within the stem and at the right time.
If you know how to prune basil, skip this section, if not check the full guide below. I add some interesting illustrations hoping to make the point clear.
Can dogs eat basil? Basil is not known to cause any health problems to dogs. However, a small dog eating for any reason a large amount of basil (many cups) can result in kidney issues.
How long basil lasts? Basil is an annual herb that lasts 10-11 months with proper pruning. Less, if not pruned
Can basil be transplanted? It is recommended to transplant the basil only once (from its seedling tray to its final planter). This to reduce transplant stress and other issues.
Can basil and mint be planted together? Despite being possible it is not recommended as basil and mint have different water needs and lifespan.
I hope you learned the basics to take care of basil! For some cool advanced tricks check the article below
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