How to grow basil indoors
If you are new to indoor gardening or looking to add fresh flavor to your recipes year-round growing herbs indoors in containers is a great project to tackle. Given the right conditions – lots of sunshine, good growing substrate, and adequate moisture – herbs grow well indoors, providing a bounty of harvestable foliage.
Basil is a great herb to start with. It is the most frequently grown herb because of its easy growing nature and abundant culinary uses.
Basil plays a key role in Italian cooking. It is paired frequently with tomatoes – think Caprese salad, bruschetta, or marinara – and used in many pasta dishes. Growing your own provides a fresh supply in your kitchen regardless of the season; any extra preserves exceptionally well in oil or by freezing.
The following information will help you get started on growing basil indoors!
Best growing conditions for basil
Native to the tropical regions of India, basil prefers sunny, warm conditions. Providing the right amount of sunlight and the correct ambient temperature encourages strong, healthy growth of plants and the best tasting foliage.
Basic plants naturally grow well outside when planted in the late spring, to thrive during the hot summertime conditions. As temperatures drop in the fall and day lengths start to shorten, grow decreases and will halt come winter. To grow plants indoors it’s important to mimic the conditions of summertime. Provide plants with plenty of sunlight - supplementing with grow lights if necessary - and keep them in a warm location.
Outside, basil plants love full-sun locations; when growing indoors they prefer 6 hours of sunlight a day, at the minimum. When choosing a home for you basil plants stick to the south or west-facing windows inside your house for the best sun exposure.
South facing windows provide the most sunlight 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. Adequate sunlight is needed to drive photosynthesis – the process of converting carbon dioxide and water into sugar plants use for food..
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.
Research demonstrates a 106% increase in fresh weight and a marked increase in the flavor of basil plants grown at 28°C compared to those grown at 18°C.
Supplies for growing basil indoors
With a few basic supplies, it’s easy to start growing basil plants. Supplies are similar for growing full-sized plants or microgreens with a couple of exceptions.
Choose from either clay (either glazed or unglazed) or plastic pots based upon your personal preference and style for growing full-sized basil plants. If growing a single plant an 8-inch pot is sufficient; 3 plants can be grown together in a 12-inch container. Choose shallow, wide containers for growing microgreens.
For more on choosing the right pot check out our complete pot selection guide.
Commercial potting mixes and coconut coir both make excellent substrates for growing either plants or microgreens. Contrary to their name, potting soils contain no soil but are a mix of peat moss or coconut coir, pine bark, perlite, and vermiculite.
Coconut coir is a renewable material made from the brown and white fibers found between the shell and the outer coating of a coconut seed. Both media are lightweight with excellent moisture retention.
To learn more about the best types of soil and growing media read our post on growing media.
Plants and seeds
Basil can be started from seeds for either end use or propagated through plant cuttings if you are growing full plants.
Plants need a high amount of sunlight when grown indoors, to see maximum growth and yield. Often times indoor spaces cannot provide the full-sun conditions similar to growing outside; in this case, plants should be supplemented with light via grow lights.
Basil responds well to either fluorescent or high-intensity discharge (HID) growing lights. Simple setups can be purchased online or a local gardening center.
The instructions for planting basil varies slightly depending on the method and the desired end result. As mentioned previously full-sized plants can be grown via seed or stem cuttings; microgreens require planting seeds.
Starting full-sized plants
Growing basil from either seeds or stem cuttings are both simple methods with the big difference being in cost: seeds have to be purchased, while stem cuttings are free if you have access to healthy plants.
Starting basil from seeds follows basic planting methods:
- Fill the container(s) with the pre-moistened growing media of your choice.
- Sprinkle a small number of seeds across the top of the substrate. There is no need to cover them, the light helps germination.
- Place container(s) in an area where the ambient temperature is at least 70℉.
- Keep the soil moist but not saturated. Too much water pushed air out of the growing media in the root zone, causing oxygen deficiencies.
- Thin plants when they reach a couple of inches tall. Keep the single, best-looking plant for an 8-inch container. Keep the three best-looking seedlings for a 12-inch container spacing them as far apart as possible. Fresh market basil was shown to have the highest yields when plants are spaced 20 cm (~8 inches) apart.
To start basil plants from stem cuttings follow these directions:
- Take a 4-inch stem cutting right below a node and remove all of the leaves from the bottom 2 inches of the stem.
- 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.
- Fill the container(s) with pre-moistened growing media of your choice.
- Carefully plant newly rooted cuttings in the substrate, 1 cutting per 8-inch pot and 3 per 12-inch container.
Starting basil as a microgreen:
- Fill your shallow container(s) with the pre-moistened growing media of your choice.
- Sprinkle basil seeds liberally on top of the substrate, there is no need to cover them.
- Place the container where the growing media can stay moist and warm.
- Harvest when first true leaves open and plants are 1-2 inches tall. This occurs in approximately 2 to 3 weeks.
Basil microgreens require very little care other than planting seeds and keeping the growing media moist until the sprouts are harvestable. Full-sized plants are also low maintenance but their longer life span require more care using the following tips.
- Water containers when the soil is dry to the touch. Basil is native to tropical regions but cannot sit in saturated growing media.
- 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 – there is no need to fertilize microgreens. Container-grown plants utilize all of the nutrients in the growing media quickly, especially quickly growing herbs so it’s necessary to replenish the nutrients needed for growth.
Harvesting and preserving basil
Basil plants respond well to frequent harvesting; regularly removing foliage from your plants will trigger new growth, encouraging full, bushy plants.
Harvesting basil is straight-forward as with many other indoor grown herbs.
- Harvest in the morning if possible.
- Using clean, sharp scissors or even your fingernails, snip or cut off stems right above the node where a pair of leaves originates. Do not leave a stub of the stem on the plant.
- 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, making sure to remove no more than ⅔ of the plant at any given time.
- For the best flavor, harvest basil leaves before plants flower. If they do flower, remove flowers and wait to harvest for a couple of days.
After harvesting you can opt to use your fresh basil, or you can preserve it by drying it, freezing it, or preserving it in oil.
Drying basil can either be done in a food dehydrator, or by air-drying. Once dried, crush the leaves and store in an air-tight container for use.
- To dry it in a food dehydrator, place washed leaves in a single layer on the food dehydrator trays. Dry at the recommended temperature until 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 light or dark room where the temperature is warm and the humidity low.
Check out our full guide on how to dry herbs.
Frozen basil is used in recipes the same way as fresh, although freezing it causes it to shrink slightly so a smaller amount should be added to a recipe.
- Remove whole leaves from the stems, and blanch for two seconds, immediately placing leaves in an ice bath afterward. Dry completely and store in an airtight container or freezer bag, separating layers with wax paper.
Preserving in oil
Preserving in oil is a great option for adding a small touch of basil flavor to dishes without overpowering other flavors.
- 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 stronger flavor.
Use immediately, refrigerate in a glass container for up to a week, or freeze in ice cube trays.
One of the most commonly grown herbs, basil is known for its role in tomato-based recipes and pasta dishes. As a native plant to tropical regions of India, basil’s low tolerance to cold temperatures and easy growing nature makes it a great plant to grow indoors providing the ambient conditions are warm and sunny. Depending on your needs basil can be grown as full-sized plants or microgreens.
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Smithsonian Science Education Center STEMvisions Blog. (2017, April 12). Retrieved January 7, 2019, from ssec.si.edu ↩︎
Mortensen, L. M. (2014). The Effect of Air Temperature on Growth of Eight Herb Species. American Journal of Plant Sciences, 5, 1542-1546. doi: ajps.2014.511168 ↩︎
Davis, J. M. (1993). In-Row Plant Spacing and Yields of Fresh-Market Basil. Journal of Herbs, Spices & Medicinal Plants, 2(1), 35-43. doi: 10.1300/J044v02n01_05 ↩︎