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How to grow Thai basil indoors

How to grow Thai basil indoors

A cousin of the commonly grown sweet basil, Thai basil (Ocimum basilicum) is becoming a popular herb grown in home gardens as culinary tastes expand. Like so many other herbs it’s easy to grow inside as long as its primary sunlight and temperature requirements are met.

For optimum growth indoors, Thai basil plants need 6 to 8 hours of direct sun exposure and daytime temperatures between 72-85°F. Grow plants in clay or plastic containers, keeping well-draining growing media consistently moist.

Read on for step-by-step indoor growing instructions, uses, and a comparison of Thai basil to different basil types.

Thai basil in bloom
Thai basil in bloom

Supplies needed for growing indoors

With a few basic supplies, it’s easy to start growing Thai basil plants for your herb garden. Supplies are similar for growing most other herbs.

Containers

Choose from either clay (either glazed or unglazed) or plastic pots based upon your personal preference and decorating style. A 6-inch pot is sufficient for a single plant; 3 plants can be grown together in a 12-inch container. Regardless of the material the container is made from, make sure it has drainage holes.

Our favorite pot for growing herbs is the 8” Bloem planter; you can buy it at Amazon here.

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Growing Media

Commercial potting mixes and coconut coir both make an excellent substrate for growing plants. Both media are lightweight with excellent moisture retention. Fox Farm is one of our go-to potting soils; we find that it works especially great in container growing. You can purchase it here on Amazon.

To learn more about the best substrate for container-grown herbs, read our post on growing media.

Plants

Thai basil can be started from seeds purchased online or at your local garden center or propagated via plant cuttings.

Supplemental lighting

Plants need a high amount of sunlight when grown indoors for maximum growth and yield. Oftentimes indoor spaces cannot provide the full-sun conditions similar to growing outside; in this case, plants should be supplemented with light via grow lights.

If you’re looking for a good supplemental grow light, we recommend this one that you can find on Amazon.

Planting Instructions

The instructions for planting Thai basil vary slightly depending on the method and the desired result. As mentioned previously, full-sized plants can be grown via seed or stem cuttings.

Starting Thai basil from seeds:

  1. Fill container(s) with pre-moistened potting soil.
  2. Sprinkle a small number of Thai basil seeds across the top of the mix and cover lightly.
  3. Place container(s) in an area where the ambient temperature is at least 70°F to promote the seeds to germinate.
  4. Keep the soil moist but not saturated. Avoid using a water can until after the seeds sprout since it displaces the growing medium and seeds.
  5. Thin plants after the first set of true leaves emerge, and the basil seedlings reach a couple of inches tall. Keep the single, best-looking plant for a 6-inch container, the three best-looking seedlings for a 12-inch container.

Starting Thai basil from stem cuttings:

  1. Take a 4-inch stem cutting right below a node and remove all of the leaves from the bottom 2 inches of the stem.
  2. Place the cut end of the stem in a glass or jar of water, allowing it to grow until newly generated roots are a couple of inches long.
  3. Fill the container(s) with pre-moistened growing media of your choice, carefully planting the rooted cuttings.
Several large thai basil plants on farm

How to grow indoors

Native to the tropical regions of southeast Asia, Thai basil prefers full sun, warm conditions similar to the sweet basil commonly grown in gardens and kitchen windowsills.

Thai basil plants grow well outside when they can take advantage of the hot summertime temperatures and long days. Growth naturally declines as temperatures drop in the fall and day lengths start to shorten; in most zones, the growing season wraps up in the late fall, and growth halts entirely in the winter.

To grow Thai basil plants indoors, it’s essential to mimic the outdoor conditions of summertime. Provide plants with plenty of sunlight - supplementing with grow lights if necessary - and keep them in a warm location to encourage robust and healthy growth of plants and the best tasting foliage.

Light Requirements

Adequate sunlight is needed to drive photosynthesis – the process of converting carbon dioxide and water into sugar plants use for food.[1]

When growing Thai basil indoors, plants require a minimum of 6 hours of direct sunlight a day. Position plants in a south or west-facing window if possible.

South-facing windows provide the most sunlight exposure in homes, with light streaming through them all day. Windows facing westwardly receive a long period of direct sunlight but often miss the hottest, most intense part of the day, making them a great alternative.

If your home doesn’t have enough direct light from the sun for your basil plants, purchase a simple growing light to supplement natural sunlight.

Temperature Needs

Basil plants are very sensitive to cold temperatures. They thrive in conditions between 72-85°F. During winter months, keep them away from drafty windows or frequently opened doors that let in cold air. Even a short dip down to 50°F will impede growth for a length of time afterward.

Caring for your Thai basil plants

Thai basil plants are relatively low maintenance when grown indoors.

  • Water containers when the potting soil is dry to the touch. Thai basil is native to tropical regions but prefers a well-drained potting mix.
  • Avoid getting water on the foliage when watering the plants. Water the soil directly if possible.
  • Fertilize plants every 4-6 weeks using a water-soluble fertilizer at half strength.
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Harvesting

Thai basil plants respond well to frequent harvesting; regularly removing foliage from your plants will trigger new growth, encouraging full, bushy plants. Regular harvesting also makes it so there is no need to prune the plant.

  • Harvest mid-morning on a sunny day when essential oils are at their peak.
  • Using clean, sharp scissors or even your fingernails, snip or cut off stems right above the node where a pair of leaves originates.
  • Periodically pinch off branch tips to encourage your plant to grow outward instead of upward for a fuller shape.
  • If plants are overgrown, you can do a more severe harvest. Starting from the top of the plant, begin harvesting stems, taking the plant down to 6 inches tall. Never cut into the woody parts of the stem; the plant won’t resprout.
  • For the best flavor, harvest basil leaves before plants flower. If they do bloom, remove flowers and wait too harvest for a couple of days.

Storage Methods

After harvesting, you can opt to use your fresh Thai basil, or you can preserve it by drying it, freezing it, or preserving it in oil.

Drying

To dry it in a food dehydrator, place washed leaves on the food dehydrator trays in a single layer. Dry at the recommended temperature until the leaves are crispy.

To air dry, bind a clump of 6-inch long stems together to create a bunch. Punch some holes in a small paper bag and place the bunch inside the bag; the bag will catch any leaves that fall off. Hang the bag in a dimly lit or dark room where the temperature is warm and the humidity low.

To learn more about the different drying methods, check out our how to dry herbs guide.

Freezing

To freeze Thai basil, remove whole leaves from the stems, and blanch for two seconds, immediately placing leaves in an ice bath afterward. Dry thoroughly and store in an air-tight container or freezer bag, separating layers with wax paper.

Preserving

To preserve in oil, place blanched basil leaves in a blender or food processor, adding 1 to 2 cups of olive oil and a ½ teaspoon of kosher salt for each cup of basil. Pulse until blended. Then strain the mixture or leave it as it is for a more robust flavor. Use immediately, refrigerate in a glass container for up to a week, or freeze in ice cube trays.

Uses for Thai basil

Like other basil varieties, Thai basil is typically grown for culinary uses, but it also has medicinal properties. Its striking physical appearance—primarily its stunning purple flowers—also lends it to be a beautiful ornamental piece as a houseplant.

Culinary uses

Thai basil is used in cuisine originating from Thailand, Vietnam, Laos, and Cambodia. It is common in stir-fries and soups such as pho. Most recipes call for fresh Thai basil but dried or frozen can be substituted if necessary.

Medicinal uses

Leaves can be bruised and the aroma inhaled, or the bruised leaves can be rubbed across the forehead and beneath the eyes to promote relaxation.

Differences between Thai basil and other types

A member of the mint family, basil is available in over 40 different cultivars with varying characteristics. Some of the favorite varieties of basil grown are sweet basil, lemon basil, Genovese basil (a variety of sweet basil), holy basil, Thai basil, and opal basil.

Thai basil is known for its differing flavor, appearance, and ability to hold up better in culinary uses.

Thai basil has a more robust flavor profile and aroma than the more commonly grown, sweet basil. Its flavor is described to be anise or licorice-like and is spicier in nature. Sweet basil has larger, brighter green, shiny leaves – the hallmark of Italian cuisines and pestos.

Plants have small, narrow leaves, dark purple stems, and pink flowers. The leaves smell like anise; essential oils present in leaf tissues have the highest odor intensity of the basil types. [2] The most popular cultivars found in stores and markets have dark green leaves and white flowers; plants have a rich, spicy, pungent aroma.

It also holds up better under higher temperatures and prolonged cooking times than other types of basil, especially sweet basil.

FAQ

Is Thai basil the same as sweet basil?

No, Thai basil is not the same as sweet basil. It’s flavor is more robust and spicier, with an anise or licolice-like taste. The plants also has smaller, darker green leaves and purple flowers. Sweet basil has larger, bright green leaves and white flowers. Thai basil also holds up better when cooked compared to other basil varieties.

Can I use Thai basil instead of regular basil in recipes?

Technically, yes, you can use Thai basil in place of regular basil but it will change the flavor of the dish slightly. Thai basil has notes of licorice and is spicier overall than sweet basil. This difference in flavor is less noticeable in some dishes, but quite apparent when used in pesto.

How long does it take to grow Thai basil from seed?

When started from seed, it takes approximately 60 to 90 days for a Thai basil plant to get large enough to harvest. Plants will grow quicker in warmer temperatures and higher sun exposure, than those grown in cooler rooms with less available sunlight.

Woman reading The Enthusiast's Guide to Herbs on her iPad

The enthusiast's guide to herbs

We’re proud to present our new e-book, The Enthusiast’s Guide to Herbs! Learn everything you need to know about growing and caring for herbs indoors, including in-depth info cards for the 35 most commonly grown herbs.

Click the link below to find out more!

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  1. Xiao, Zhenlei, Gene E. Lester, Yaguang Luo, and Qin Wang. 2012. “Assessment of Vitamin and Carotenoid Concentrations of Emerging Food Products: Edible Microgreens.” Journal of Agricultural and Food Chemistry 60, no. 31: 7644–51. https://doi.org/10.1021/jf300459b. ↩︎

  2. “What Is Photosynthesis.” Smithsonian Science Education Center, March 27, 2018. Accessed October 20, 2021. https://ssec.si.edu/stemvisions-blog/what-photosynthesis. ↩︎

Amanda Shiffler
About the author

Amanda Shiffler

With an M.Sc. degree in agronomy and over a decade of experience gardening, Amanda combines her plant knowledge and knack for writing to share what she knows and loves.