How to grow basil indoors (for year-round supply)

When you understand how to grow basil indoors you will never have to buy another basil plant again.

We grow basil year round and so can you. Regardless of your level of expertise – yes, even true beginners – can follow our guide to have fresh basil on tap year round.

This article will focus on caring for and growing basil plants indoors. We will go cover every step from the sprouting of first leaves to harvesting this wonderfully aromatic herb for use in salads, pesto. seafood dishes, pizza, vegetable soups and the list goes on.

Starting basil from seeds is the most common - and traditional method - to grow basil. But indoor basil can also be grown from cuttings and is - along side lettuce - the ideal choice if you are interested in learning about hydroponics. 

Growing basil plants indoors

Growing basil indoors is in many ways similar to growing basil outdoors. There are however two main differences.

On the plus side the growing season is year round as long as you can find a way to make up for the lack of direct sunlight during the darker times of the year.

Growing sweet or common or Genovese basil indoors
Growing common, sweet or Genovese basil indoors

But this longer growing season also means that you have to use a grow light to overcome the lack of natural sunlight for the darker periods of the year.

Basil wants a fertile soil that drains well. And always use a pot with drain holes made from a material that breathes like terra cotta.

Find detailed guides on how to grow basil and Thai basil in the article archives. You can alos use soil less potting soil mixes like coconut coir to start basil from seed.

Step 1: Waiting for basil seeds to germinate and sprout

Basil seeds are delicate and you should avoid top watering using a regular watering can. Instead, mist the pot using a spray bottle or bottom water your pots.

Covering the pots with clear plastic is an effective way to ensure moist soil.

When bottom watering, remove the pot when the dry soil has absorbed enough moisture indicated by a change to a darker soil colour. Next, let the pots drain any excess. It is key to keep the soil moist, but not wet.

Basil seeds germinate within a week or so and do not need any fertilizer to sprout.. 

Step 2: Even a sprouting basil plant needs light to thrive

When you see first leaves, remove cover and place pots in a spot with sufficient light.

Basil needs a minimum of 6 hours of natural sunlight to grow and thrive. And as soon as the seeds germinate and you see the formation of first leaves you need to get your lighting in order.

Opal basil grown under grow light indoors
Opal basil grown under grow light indoors

Growing basil indoors you have two choices:

  1. place the young seedlings in a south facing window with sufficient natural light
  2. use a grow light to give your basil pants enough light

We use grow lights during the darker periods of the year. Always check the level of heat generated by your grow light fixture before finalising the placement of the grow light.

But as a rule, placing grow lights closer to your plants will give more effect.

Needless to say a south facing window will only give sufficient light if you live in the northern hemisphere. Should you instead live in the southern hemisphere, place your pots in a north facing window.

Step 3: Transplanting basil seedlings to a larger pot

It is time to pot up or repot your basil seedlings when they have developed a minimum of two pairs of true leaves.

When possible, I do not prick out the seedlings but simply transplant the whole starter pot into a larger pot.

Basil plants do not like cold temperatures or windy conditions. Try keep the temperature in a range between 23-28 degrees Celsius (73-83 F) when growing basil indoors.

Opal and Thai basil seedling readu for transplant to bigger pots
Opal and Thai basil seedlings ready for bigger pots

Be mindful of windows with a draft during winter when growing basil indoors. In cold temperatures below 10 degrees Celsius (50 F) your basil plant will suffer and might even die.

Basil does not take well to dry soil why soil amendments that help maintain a constant level of moisture are helpful. Adding peat moss or vermiculite can help keep the soil moist.

Make sure that you provide sufficient light for your basil plants to grow strong and compact.

I like my basil plants to grow large and bushy. If needed I thin out weaker plants - and they do make for delicious eating.

Step 4: Harvesting basil plants is key

When you grow basil indoors you want compact and bushy plants. And here the key is to continuously harvest your plants.

Continuous harvesting helps stimulate new growth and also help the basil plants to grow bushy. Always use sharp and clean scissors and harvest outside-in when harvesting individual leaves.

Why not harvest branches and use the stem cuttings form to use for growing even more plants? Using stem cuttings is a fast and very effective method of growing basil indoors. 

Step 5: Basil plants and choice of fertilizer

Continuous harvesting will stimulate the basil plant to grow stronger. But your basil plants will need an infusion of energy to keep producing leaves for you to harvest.

I recommend adding nutrition in the form of an organic fertilizer starting after your first harvest. Basil responds well to liquid fertilizers.

As always, start with half the recommended dosage to one single plant and observe the effect to minimize the risk of shocking your basil plants. You can always add but it is complicated to balance overfertilized soil.

When you have found a balance that works for your plants your should add the same organic fertilizer every 4-6 weeks.

Step 6: Prune and care for your basil plants

Basil plants grow well and keep producing new heathy growth for you to harvest as long as you

  1. provide fertile soil that drains well
  2. ensure plants have sufficient light
  3. maintain moist – but not wet – soil
  4. prune and harvest your plants regularly

Basil needs to be pruned regularly to help the plant grow bushy and compact. After about 6 months of so, your basil plants may decide to flower, produce seeds and die off.

Prune or harvest mature leaves to let younger leaves grow and develop
Prune or harvest mature leaves to allow young leaves to develop

By pruning flower stalks and topping your plant you can successfully extend the lifespan of your plants for several weeks.

You will know when it is too late to save your plant as the stems grow woody and the basil leaves grow yellow.

Best basil varieties to grow

There are so many great basil varieties to chose from. It is actually quite difficult to crown the best variety to grow. But from all the varieties we have grown over the years, these 3 are my favourites

  1. Common, sweet or Genovese basil – large aromatic leaves, perfect for salads, sublime with tomatoes, ideal for pesto
  2. Thai basil – sturdy aniseed flavoured leaves, great in salads, stir-fry’s or cooked with chicken or tofu
  3. Opal basil – purple leaves, sweater taste, great for infusing vinegars and oils, favorite with pasta dishes

Summary: Growing basil indoors

Basil is probably the most popular aromatic herb grown by home gardeners. And it is easy to understand why. Basil is such a versatile herb. Take basil and add tomato slices, mozzarella cheese and sprinkle a good quality olive oil on top and you have a Michelin star quality dish..

And if you only take one thing from this article, please let it be that basil and indoor gardening in general requires more hours of light than you will get naturally.

If your basil leaves show signs of yellowing or lack of new growth you should look at the plants exposure to light.

3 ways to grow basil indoors
Thai basil plant grown indoors with large and vibrant basil leaves

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants, and garden vegetables. For the past two years, he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.