Growing Thai Basil Indoors: Propagation and Plant Care!

Are you planning on growing Thai basil indoors? Then don’t think twice; this herb can easily grow inside, just like its mother – the common basil.

Thai basil is a very resilient and easy-going variety of basil. In fact, many gardeners consider growing Thai basil to be much simpler than growing other varieties of the herb.

Nevertheless, every single plant requires care and attention, and our Thai basil is no exception. Proper plant maintenance for Thai basil includes watering, feeding, and pruning.

We’re going to help you discover how to do all of that and more. This article has been written to help guide you through the different steps of propagating and taking care of Thai basil indoors.

By the time you’ve finished reading, you will feel confident enough and fully ready to grow your own Thai basil indoors.

Propagating Thai Basil

You can propagate Thai basil either from seeds or from cuttings, and we are going to show you both ways here.

If you are planning on buying a fully established plant, or if you have already got your Thai basil somehow, then you can skip this first step.

Growing Thai Basil from Seeds

Propagating Thai basil in this way is both easy and inexpensive. Seeds are usually very cheap and can be easily acquired.

That being said, this isn’t necessarily the most effective method of growing this herb.

Usually, Thai basil seeds have a relatively low germination rate. However, that doesn’t mean that you can’t succeed in growing Thai basil from seeds (or else we wouldn’t have mentioned that here!).

All that means is you may need to do a little bit more work, and add some further resources to increase the likelihood of your success.

growing thai basil indoors
  • Obtaining the Seeds

The success of this operation will depend largely on how good your seeds are. This is why we always advise people to go for higher quality brands of seeds.

Factors such as cultivation, storage, and the age of your seeds will determine their germination rate later on.

For example, if the seeds were stored in an imbalanced environment for a long period of time, then they will have zero chance of germinating.

To avoid such problems, you should inspect the quality of the seeds before purchasing them. The best, and most simple, way to do this is by picking the brand of seeds that has the most positive reviews online.

  • Obtaining the Medium

Using just any type of soil to propagate your Thai basil is a very risky thing to do.

While growing your seeds in garden soil is entirely wrong, using potting soil isn’t the best thing to do either.

When propagating Thai basil, the main concern here is to avoid putting your seeds at risk of contracting a disease.

Some soils are brimming with harmful pests and pathogens that can prevent seeds from germinating or producing healthy seedlings.

To combat this, experts recommend using a seed-starting mix, which is a well-drained and sterile soilless mix.

Seed-starting mixes are composed of different materials that can drain water efficiently, and thus prevent seeds from rotting.

From experience, we can tell you that Black Gold Seedling Mix is one of the best blends you can use for Thai basil seeds. You can find it here on Amazon:

Black Gold Seedling Mix

  • Sowing the Seeds

Prepare the seed-starting mix by moistening it with warm water. Be careful as to how much water you put in because the mix shouldn’t become too soggy.

Next comes your containers. You can either buy some seed-starting trays, or you can reuse everyday things that you may already have at home, such as milk or juice cartons.

Any shallow containers can work but be sure to create sufficient drainage holes in them. 

Fill your containers to the rim with the moistened mix, and sow your seeds on top of each of them. Use four to five seeds for each 1.5 x 1.5-inch container.

growing thai basil

Once you’re done, cover your seeds with a quarter-inch of soil, spray them with water, then place a plastic wrap over the containers.

  • Caring for the Seeds

Keep your seeds in a warm place, away from the reach of intense and direct sunlight.

Let the seeds breathe by uncovering the plastic wrap for a few hours each day. Meanwhile, spray the mix with water in order to keep the humidity levels around your seeds as high as possible.

After a week or two, your seeds will germinate, and then the seedlings will be ready to move to different pots.

Growing Thai Basil from Cuttings

Growing Thai basil from cuttings is a much more effective way than growing it from seeds, and in our opinion, it’s easier too.

The only drawback here is that you will need to have a fully established Thai basil plant from which to obtain your cuttings.

If you’re lucky enough to have a friend or relative who grows Thai basil, you may be able to ask them to bless you with some cuttings for you to grow.

If not, then no problem. You can buy a Thai basil plant from a nursery and wait until it grows old enough to produce some cuttings.

  • When and How to Take Thai Basil Cuttings

Knowing when to take your Thai basil cuttings is a fairly simple decision. Wait until the plant has grown at least four inches tall or has developed no less than four sets of leaves on most of its branches.

In this condition, the cuttings you take will be strong enough to initiate rooting and become independent plants.

Pick any stem you wish, but make sure it’s healthy and strong. Count three or four sets of leaves – starting from the top – then produce a cut just below the last one.

Note: Avoid waiting until the plant has developed flowering buds to take your cuttings.

  • Propagating the Cutting

Remove all the leaves at the bottom of the cutting and keep two sets of leaves growing at the top.

Afterward, you should immerse the cutting in a glass of water. Keep it away from direct sunlight and be sure to change the water every other day.

After two to three weeks, the cutting will grow a well-developed root system. At this point, it will be ready to be moved to a pot so that it can grow as a plant.

Note: Once you have moved the cutting to its own pot, you must make sure that you keep it away from light for 48 hours so as not to stunt its growth.

Caring for Thai Basil Indoors

When it comes to success in growing Thai basil indoors, it all depends on how well you look after the plant.

In this section, I’ll discuss all the factors that play an important role in the survival and development of Thai basil inside, so that you will be fully prepared to care for the plant.

Soil and Nutrition

The medium your Thai basil grows in is one of the most important factors in its development, especially if it is contained in a pot.

Here, choosing the ideal soil for your Thai basil improves the plant’s survival chances, growth rate, flavor, immunity to disease, and much more.

Practices have shown that Thai basil grows best in moderately well-drained and rich soil.

We recommend the popular Foxfarm Ocean Forest® Potting Soil as it has those exact properties and is very suitable for your plant.

Foxfarm Potting Soil

  • soil

Nevertheless, in a few cases, the plant may not grow so well in its potting soil.

If this is the case for you, adjust the drainage of the soil by adding either water-trapping material such as vermiculite, or water-draining material such as perlite.

At the same time, you can’t leave your Thai basil without feeding it on a regular basis.

You need to fertilize and amend the soil (after you change it) every two to three months.

You can use vermicompost, Alfalfa meal, kelp, or any other natural fertilizer of your choice.

Light

Light is probably the most controversial and complicated issue when it comes to growing herbs indoors.

What makes this even more challenging is that mature Thai basil requires long periods of exposure to direct sunlight in order to flourish.

Thai basil

If you can’t find a sunny location indoors that provides at least six hours of direct sunlight, don’t give up on growing Thai basil too quickly, as luckily we live in the age of technology and innovative solutions!

Grow lamps have been invented and optimized solely for the purpose of helping you grow your favorite plants and herbs inside your home.

Full-spectrum LEDs or fluorescent lamps, for example, are all highly suitable for your Thai basil.

That being said, whilst you can grow your Thai basil completely under grow lamps, it’s better to make the most out of the sunlight that is entering through your windows.

In other words, try to aim for a combination of sunlight and artificial light to satisfy your Thai basil needs.

Remember that six hours of sunlight is equivalent to 12-14 hours of artificial light.

So, if your basil plant is getting four hours of light from the sun, you should then aid it with an additional four to eight hours of light from your grow lamp.

Temperature and Humidity

Because you’re growing your Thai basil indoors, you will need to be extra careful about the levels of temperature and humidity that are fluctuating around your plant.

A temperature of around 75°F (24°C) during the day is optimal for Thai basil. That temperature should then drop at night to somewhere around 68°F (20°C).

In any case, it’s better to avoid growing Thai basil at a temperature below 68°F (20°C) during the day, and 64.5°F (18°C) during the night.

When it comes to humidity, it’s much more preferable to keep the levels of moisture in the atmosphere at around 40-50%.

You can easily measure the humidity levels in your home by using a hygrometer.

To adjust the temperature and humidity, you can use an air conditioner, radiator, humidifier, or dehumidifier.

Watering

Watering Thai basil in pots is very different from watering it in the garden, and here is where all the mistakes can happen.

Overwatering and underwatering are two very common issues when it comes to growing this herb.

One of the biggest problems here is that people stick to a watering schedule that is usually not suitable for the growth of Thai basil.

For example, if the temperature isn’t really high, you can’t water this herb daily, whereas, in hot weather, you might need to water Thai basil twice a day.

The best way to know when to water your Thai basil is by simply monitoring the soil on a daily basis. Just use your finger to feel the soil in the container each day.

Water your Thai basil the day the soil becomes dry. This way you can ensure that you’re giving your plant the optimal amount of water. 

Pruning

Pruning is one of the most important activities in herb gardening, and your Thai basil’s productivity depends hugely on pruning.

The good news here is that this plant is pruned just the same as common basil.

If you don’t know how to cut back basil, you can learn about it in this article we wrote on pruning basil!

Transplanting

Thai basil’s roots grow almost at the same rate as its leaves and stems do. So, if the pot isn’t big enough, at some point your plant’s roots will bump into the wall of the container.

If your Thai basil gets rootbound for a long period of time, it might eventually die. In this instance, transplanting your plant to a wider pot is crucial.

And that’s it! Enjoy cultivating your Thai basil, and don’t forget to share your thoughts and experiences in the comments below!

Additional resources: How to Grow Basil Indoors Year Round! (TheGreenPinky.com)

Blogger, Gardener | + posts

I'm Jad, a biologist, blogger, and experienced indoor gardener. I am knowledgeable in plant biology, particularly in plant cultivation and propagation. I founded HerbsWithin.com in 2019 to share my knowledge in indoor gardening with passionate home growers.

2 thoughts on “Growing Thai Basil Indoors: Propagation and Plant Care!”

  1. My Thai Basil plants their stems are all turning black! What’s the reason? I had to bring them inside because of the cold weather & I do not water them as much as I did when they were outside! Please help?

    Reply
    • I believe this is a case of root or stem rot that is most likely caused by a fungal disease due to lack of proper drainage and/or ventilation. It might be already too late to save the plant but try to remove the affected stems as soon as possible.
      Good luck!

      Reply

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