How to grow basil indoors and keep it bushy

What you need to grow basil indoors

Basil needs 4 things indoors: strong light, warmth, a pot that drains, and steady water. This guide is for sweet basil, the kind used for pesto. Thai basil grows the same way and handles heat better.

Need	What to do
Light	6 to 8 hours of direct sun, or a grow light for 14 hours a day
Warmth	70°F or more by day, never below 50°F
Pot	6 inches wide or more, with drainage holes
Soil	Bagged potting mix, not garden soil
Water	When the top inch is dry, in the morning
Food	Weak liquid plant food every 2 weeks
Harvest	Cut above a leaf pair, never more than a third of the plant

Our basil plant profile sums it up on one page. The same basics work for most kitchen herbs, as our guide to growing herbs indoors shows.

How much sun does basil need indoors?

Basil needs 6 to 8 hours of direct sun a day. A south-facing window is best, and a west-facing one is next best. East and north windows do not give enough light on their own.

In winter, even a south window falls short, so add a grow light.

Set a grow light on a timer for 14 to 16 hours a day. Hang it 6 to 12 inches above the top of the plant.^[1] If you are not sure, start with 14 hours. LED lights vary, so check the maker’s guide for how high to hang yours. Our guide to choosing a grow light compares the main types.

Too little light makes basil tall and floppy, with big gaps between the leaf pairs. Turn the pot every few days so it does not lean toward the glass.

Keep basil warm (below 50°F it gets damaged)

Keep basil at 70°F or warmer, and never let it drop below 50°F. Basil is a tropical plant, and cold hurts it fast.^[1]

Cold damage shows up as black, soft patches on the leaves a day or two after a cold night.

The trap is the window. A room can feel warm while the glass is cold. On winter nights, the air by the glass can drop below 50°F. So pull the pot back from the window at night, or move it to a table. Keep the leaves off the glass.

Keep it away from drafty doors and AC vents, too, and from hot, dry heater vents.

Leaves with cold damage will not recover. Pinch them off, and new growth will take their place.

The best pot and soil for basil

Use a pot at least 6 inches across, with drainage holes, for 1 plant. A 12-inch pot holds 3 plants. A bigger pot grows a bigger plant, and it dries out more slowly.

Plastic and glazed pots hold water longer. Clay dries out fast, so check it more often in summer. If you like clay, these 6-inch clay pots come with mesh pads that keep soil in. Our guide on how to pick a pot for herbs compares the options.

Fill the pot with bagged potting mix, never garden soil. Garden soil packs down hard in a pot and drains badly. Fox Farm potting soil is a good bagged mix. For extra drainage, mix 2 parts potting mix with 1 part perlite. Perlite is the light white grit that keeps soil loose. For more choices, see the best potting mixes for herbs.

How often to water basil indoors

Water basil when the top inch of soil feels dry. Push a finger in to check. In a sunny summer window, check every day or two. Check less often in winter.

Water until it runs out of the bottom, then empty the saucer. Watering from below works too. Just do not leave the pot standing in water all the time.

Water in the morning, and aim at the soil, not the leaves. Basil hates wet roots overnight.

Do not let the mix dry out all the way, either. Drooping leaves are the first sign that it is too dry.

Feeding

Feed basil every 2 weeks with a liquid plant food mixed at half strength. Feeding more often than that hurts the smell and taste of the leaves.^[1]

Pale, yellow-green leaves on a plant that is not too wet usually mean it is hungry. Skip tomato food and “bloom” feeds. They are high in potassium, which pushes basil to flower.

Seeds, cuttings, or a supermarket pot

A supermarket pot is the fastest start, seed is the cheapest, and cuttings are free.

How to split a supermarket basil pot

A supermarket pot holds lots of thin seedlings packed close. Left like that, they fight for space, then rot or flower early. They can survive if you split them up and repot them soon.^[2]

1. Water the pot an hour before.
2. Slide the whole root ball out of the pot.
3. Gently pull it apart into 3 or 4 clumps. The roots can take some tearing.
4. Plant each clump in its own 6-inch pot of fresh potting mix, at the same depth as before.
5. Water well. Keep the pots out of hot midday sun for the first few days.

How to grow basil from seed

Sow the seeds ¼ inch deep in damp potting mix. At 70°F, they sprout in 5 to 10 days.

Keep the mix damp. Once they sprout, move them under a light or to your sunniest window so they do not stretch.

The first 2 leaves are round seed leaves. Wait until 2 pairs of real basil leaves grow above them. Then keep the strongest seedling in a 6-inch pot, or 3 in a 12-inch pot. Snip the rest off at the soil.

How to grow basil from cuttings

Basil roots easily in a glass of water.

1. Cut a 4-inch tip from a stem with no flower buds.
2. Strip the leaves off the bottom 2 inches.
3. Stand it in a glass of water. Change the water every few days.
4. Roots form in about 2 weeks. Pot it up when they are 1 or 2 inches long.

This works with a bunch of cut basil from the store, too. It is also how you replace an old plant that has turned woody.

How to harvest basil so it keeps growing

Cut whole stem tips just above a pair of leaves. Do not pull single leaves off the bottom of the stem.

Start when the plant has 6 to 8 leaves. Leave at least 2 to 4 leaves on each stem you cut.

Where each leaf pair meets the stem, you will see 2 tiny shoots. Cut just above them, and both grow into new stems. That is what makes basil bushy.

Never take more than a third of the plant at once. Cut from the top down, and leave the big bottom leaves. Harvest about once a week, since the more you pick, the more you get. Our herb pruning guide shows the same cut on other herbs.

Keep cut stems in a glass of water on the counter, not in the fridge. Cold turns basil leaves black. To keep basil for months, freeze it after a 15-second dip in boiling water. Drying loses much of the flavor. If you do dry basil, dry it fast so it does not mold. Our guide on how to dry herbs covers each method.

Why is my basil flowering?

Flowering is basil’s natural last stage. Heat, long days, and a crowded pot bring it on sooner. Early flowering like this is called bolting.

Once the flowers open, the leaves turn bitter.^[3]

Watch the stem tips for a small cone of tight buds. As soon as you see one, cut that stem back to the leaf pair below the buds. Do not just pinch off the bud, or the plant pushes out more flowers from the leaf joints.

You cannot stop it forever. When the plant turns woody and keeps flowering, root a few cuttings and start fresh. Our guide to why herbs bolt explains what sets it off.

Why is my basil dying? Symptoms and fixes

Most indoor basil dies from cold, too little light, or too much water.

Symptom	Likely cause	Fix
Yellow lower leaves, wet soil	Too much water	Let the top inch dry. Empty the saucer.
Pale yellow-green all over, soil fine	Hungry	Feed weak plant food every 2 weeks
Yellow leaves, gray-purple fuzz underneath	Downy mildew, a leaf disease[4]	Throw it out. Next time, grow ‘Prospera’, ‘Amazel’, or ‘Devotion’.
Black, soft patches after a cold night	Cold damage	Move it off the glass. Pinch off bad leaves.
Brown, crisp leaf edges	Dry soil, or leaves on hot glass	Water more steadily. Move it back a few inches.
Tall and floppy, big gaps between leaves	Too little light	Add light. Cut back to the lowest good leaf pair.
Wilting, dry soil	Thirsty	Water well. It should perk up in a few hours.
Wilting, wet soil	Rotting roots	Check for brown, mushy roots. See root rot.
Tiny bugs, sticky leaves, or fine webs	Aphids, whiteflies, or spider mites	Rinse in the sink. Spray insecticidal soap or neem oil.
Tiny flies around the soil	Fungus gnats	Let the soil dry more. Use yellow sticky traps.

Downy mildew looks like hunger at first. Turn a leaf over, and you will see the gray-purple fuzz.

For bugs, our guide to getting rid of indoor plant pests has more steps.

Questions & answers

Can you grow basil indoors year round?

Yes. Give it a sunny window in summer and a grow light for 14 hours a day in winter. Keep it above 50°F at all times, and root cuttings to replace old plants.

Is basil a perennial?

No. Sweet basil is a tender annual, which means it lives for 1 season. It flowers, turns woody, and fades. You can keep your basil going by rooting cuttings from the old plant.

How long will basil live indoors?

Several months, if you keep harvesting the tips and cutting off flower buds. Once it turns woody and keeps flowering, start a fresh pot from cuttings.

When should I start basil seeds indoors?

Any time, if the plant will stay indoors under a light. To move it outside later, sow 4 to 6 weeks before nights stay above 50°F.

Why does my basil taste bitter?

It has most likely started to flower. Cut the flowering stems back to the leaf pair below the buds. The new leaves that grow in will taste right again.

References

1. Penn State Extension, Growing Herbs Indoors. https://extension.psu.edu/growing-herbs-indoors ↩︎ ↩︎ ↩︎

2. Royal Horticultural Society, How to grow basil. https://www.rhs.org.uk/herbs/basil/grow-your-own ↩︎

3. NC State Extension, Basil and pesto. https://brunswick.ces.ncsu.edu/news/basil-and-pesto ↩︎

4. Cornell Vegetables, Basil downy mildew. https://www.vegetables.cornell.edu/pest-management/disease-factsheets/basil-downy-mildew/ ↩︎