Basil is a must-have herb if you love pesto and caprese salad, but basil plants aren’t as cold-hardy as other culinary herbs, such as oregano and sage. In most areas, basil grows as an annual, and the plants die at the first sign of frost. However, with a bit of know-how and a few gardening tricks, you can grow fresh basil all year round and have fresh herbs on hand for your favorite basil recipes.
Is Basil a Perennial?
Most types of culinary basil are native to warm regions of Asia and Africa. They grow as perennial plants in USDA Zones 10–11. In cooler climates where frost occurs, culinary basils are grown as annual plants and don’t survive the winter. However, basil self-seeds if you allow the plants to flower.
Wild basil (Clinopodium vulgare) is a cold-tolerant plant that can survive in climates as chilly as Zone 4. It's used like culinary basil in recipes, although it has a milder flavor with hints of cilantro. Wild basil is only distantly related to culinary basil plants (Ocimum spp.), but if you want to overwinter basil outdoors in a cool area, try experimenting with this basil substitute.
How to Extend Your Basil Harvest
Because culinary basil doesn’t tolerate frost, these edible plants usually die back in early to midfall, as soon as temperatures begin to drop. However, you can shield your basil crop from the cold and extend the harvest by a few extra weeks:
- Plant nursery starts or start basil seeds indoors. Pre-started basil plants may be more expensive than basil seeds, but they allow you to harvest basil leaves earlier in the season. If you’re struggling to grow a large basil harvest before autumn frost arrives, start your herb garden off in spring with larger plants.
- Harvest often. Picking basil leaves throughout the growing season encourages the plants to branch out and sprout more leaves. Beyond that, pinching back basil regularly also keeps the plants from flowering, which causes basil plants to produce fewer leaves.
- Use season extension products. While basil doesn’t handle frost well, if the forecast is for a light frost, you may be able to protect your basil plants with season extenders and prolong the harvest by a few more days or weeks. Floating row covers, cloches, or overturned milk jugs shield plants from mild frost and keep them growing strong.
How to Grow Basil Year-Round
Most gardeners plant basil in spring and harvest the crop throughout the summer. However, if you want to extend the harvesting window and grow basil all year round, grow basil indoors and harvest fresh leaves from the plants throughout the winter months. When properly maintained, basil plants usually last about a year indoors, but they can sometimes live up to four years.
Indoor basil plants can be started from seed, stem cuttings, or nursery starts. Basil plants purchased at the grocery store usually won’t last long indoors as these plants are often root-bound and overcrowded. However, you can take cuttings from grocery store herbs and propagate them into new plants for your indoor herb gardens.
One of the great things about basil is that it thrives in pots, and you can keep a pot or two of basil on your windowsill or in a sunny corner of your kitchen and harvest leaves just as you need them for recipes. Basil plants grow best in pots that are at least 8 to 10 inches wide. Also, ensure that any container you grow basil in has plenty of drainage holes at the bottom to prevent soggy soil.
When you’re ready to plant indoor basil, choose a nutrient-rich potting mix and position started plants in the mix to the same depth they were growing in their nursery pots. If placing more than one plant in a container, space them at least 8 inches apart for a fuller look or 12 or more inches apart to allow better air circulation.
If starting plants from seed, sow the basil seeds 1/8 inch deep and thin them to 3 to 4 inches apart after they germinate.
Indoor basil needs plenty of bright light and regular watering to grow properly. If you have a sunny windowsill that receives at least 6 to 8 hours of bright light daily, that’s a great place to locate basil. Alternatively, you can pick up a grow light to ensure your herb receives the light it needs.
How to Preserve Fresh Basil
While basil is a relatively easy herb to grow indoors, if you don’t want to maintain an indoor herb garden throughout the year, harvest your entire basil crop in late summer to early fall and preserve the leaves for future cooking. Basil leaves can be frozen whole, or you can chop them and freeze them in ice cube trays. Basil also dries beautifully, and you can keep the dried leaves in your spice cabinet.
Before freezing basil, blanch the fresh leaves for 30 seconds to preserve the leaves’ texture and color. Then, pat the leaves dry and flash-freeze them before storing them in airtight packaging in your freezer.
When drying basil, it’s best to dry leaves quickly with a dehydrator, microwave, or oven on the lowest setting. Hang-drying basil is not recommended, as fresh basil can discolor when it dries slowly.
Replanting Basil in Spring
Outdoor annual basil plants often self-sow if you don’t pinch back their flowers, so you may find that new basil plants sprout on their own in your garden every spring. However, basil seeds don’t always germinate, which is why many gardeners take matters into their own hands and plant basil annually.
Basil seeds can be started indoors or outdoors in spring, or you can plant new nursery-started basil plants outdoors after the danger of frost has passed. Planting a new crop of basil every year is the best way to ensure you always have fresh basil on hand, no matter the season.
Repotting Basil
Repotting will give your basil plant room to grow out its roots and absorb nutrients. Around midsummer, you can divide the plant into smaller sections and place them into multiple containers if necessary. However, try to maintain the same soil around the roots when transplanting and backfill around the rootball with fresh potting mix. Water it to settle the plant into its new home. When the plant is established, prune it to stimulate new growth.
