How to Grow Basil
This article is part of our “How to Grow Herbs” series. If you would like to learn more about how to work with this plant after you harvest it, please refer to our Herbal Aromatherapy Certification Program™ here.
Ah, basil. I love this herb so much. As I am sitting down to publish this article, we (my husband, Jon, and I) are just preparing to harvest the last of the basil for the season before our nighttime temperatures dip below the plants’ comfort level. We will dry the leaves so we can use them in cooking throughout the wintertime and I will be eagerly looking forward to planting more in spring. I love having access to fresh basil, both for cooking and teas, as well as for distillation. Fresh basil hydrosol is such a treat!
There are many species of basil – some people believe as many as 150, not counting cultivars! Most of the basils we are familiar with as garden basils are cultivars from the species Ocimum basilicum. They are members of the Lamiaceae (mint) family.
Growth Habit
The common garden basil that we see most often grows to about 2-3 feet tall and has shiny, thin leaves with lightly toothed edges. If you brush up against the plant in the garden or rub one of its leaves between your fingers, it readily releases its spicy, fresh aroma. The flowers are arranged in whorls at the tops of the stems above the leaves and can be either white or shades of pink, depending on the variety. My purple basil varieties have pink flowers while the green varieties usually have white flowers.
Growth Requirements
In most areas, basil grows as an annual (it must be replanted every year) and appreciates well-draining, nutrient-rich soil. Soggy soil can cause fungal issues and kill the plant and soil that is too dry will lead to wilting; consistent watering paired with good drainage is best. I like to plant new seedlings with a bit of compost and BioTone (a microrrhizal fertilizer offered by a company called Espoma), which seems to help them establish healthy roots and really take off quickly.
Basil plants can grow quite large if they are happy where you have planted them. Because of this, I like to give them at least 18” spacing, but you could even go to 24”+ spacing if it grows especially well in your area.
Basil does well in full sun, but if you have very hot summers, it might do better with plenty of morning sun and a bit of partial shade in the afternoon to shelter it from sunburn. Planting between the tomatoes seems to offer some protection as the tomatoes grow taller.
Basil can also be grown in containers. They need plenty of space for root development and access to nutrients or the plant will stunt, so larger pots and good soil are best. You will likely need to feed the plant more often if you are growing it in a container. Potted basil can be brought indoors for the winter and kept in a sunny window.
Outdoors, basil grows wonderfully alongside tomatoes and it has long been thought that growing the two near each other improves the flavor of both. I like to plant basil between some of my tomato plants for this purpose.
Pruning / Pinching
Once your basil reaches 6 inches (about 15cm) in height, you can begin to regularly pinch (remove) the centers of its newly growing tips to encourage the plant to branch out and grow full. Because basil is a member of the mint family, pinching the centers of its growing tips will result in two main stems growing in the place of the single stem you pinched. Over time, pinching makes the plant grow large and bushy, which gives you more basil to harvest. It really makes for much more vigorous plants. You want to continually pinch your basil this way throughout the season to keep it from flowering. Once a basil plant starts to flower, the texture and flavor changes and the plant stops producing more leaves as it switches its focus to producing seed. Continue pinching the plant until the fall season to keep a continual supply of leaves ready for harvesting.
In the heat of the summer, the plant will try to produce flowers continuously, so any time you see those flowers starting to appear, remove them as soon as possible. Pollinators do love basil flowers, so if you can, allow one or two plants to flower and harvest from the rest. The plants that flower will produce seeds that you can collect or allow to self-sow for the next year.
Basil is very sensitive to frost and loves warm weather, so continue to harvest your plants until the frost kills them, then cut them back to the ground and compost anything that cannot be used. I like to keep an eye on the weather forecast and harvest the last of the foliage before the nighttime temperatures dip into the 30s (below 4°C). The roots will break down in the soil over time if you leave them in the ground and feed the earthworms, which will convert them into castings that nourish your soil. If you are growing basil in a container, the pot can be brought indoors and placed under a strong light source or in a sunny window for the winter and you can continue to harvest from it throughout the cooler months. It will not likely put on much new growth over the winter and you will likely need to supplement its light. Gradually acclimate the plant to the outdoors again when the frosty season has passed.
If you are lucky enough to live in a more southern region (zone 10+), your basil will likely perennialize and continue to grow indefinitely.
Growing from Seed
Basil grows very well from seed and can be direct-sown or sown into larger seed-starting pots and transplanted when it is at least 6” tall. Younger seedlings don’t much like to be transplanted. Because basil is a frost-sensitive plant, it is a good idea to start the seeds under protection around the time when you start your tomato seeds and up to about 2 weeks before your last frost date. Plant both basil and tomatoes out into the garden after your last frost date for best results.
Basil can also be propagated through cuttings. As it produces suckers throughout the season, you can cut them off and root them in water or soil to create clone plants.
Some of my favorite garden varieties of basil include:
Common garden basil / sweet basil / Genovese basil
Lettuce leaf basil (this variety produces larger leaves) / Italian large-leaf basil
Lime basil
Purple opal basil / Genovese Red Freddy basil
Thai basil
Greek basil
Learning More
If you would like to learn more about how to work with aromatic plants, I hope you will join me in our Herbal Aromatherapy Certification Program™ here at Floranella! In it, I teach students how to safely and effectively work with over 100 different herbs as well as their applicable essential oils and hydrosols from the garden to the still to the apothecary. I hope to see you in class one day!
About the Author
Hi there, I’m Erin! I am the main instructor here at Floranella. I am a clinical herbalist, aromatherapist, artisan distiller and organic gardener based in the Pacific Northwest. Here at Floranella, I teach people how to work with plants safely and effectively from the garden to the apothecary. Thanks for being here! I’m glad you stopped by.
