When Should You Plant Basil This Season?

Basil is native to Asia and can be found growing wild in tropical and subtropical regions, but due to its extensive variety of uses, it is now cultivated by growers all over the globe. Because of its heat-loving nature, basil is very sensitive to cold temperatures. 

If you’ve decided to add basil to your garden this season, you may be wondering when the best time is to start planting. This will depend on various factors, including your hardiness zone, local microclimate, and whether you decide to start seeding indoors or direct sowing outdoors in your garden.

Regardless of the planting method, extreme care must be taken when starting seeds indoors and transplanting plants outdoors. Keep reading to discover when you can safely plant basil in your region this season!

The Long Answer

Basil is a favorite among gardeners worldwide for culinary use in dishes such as pizza, pasta, and pesto. It has also become a popular ingredient in mocktails, fruit salads and has been adorning the tops of desserts for years.

However, in order to grow this aromatic herb seasonally and successfully, you should know when best to plant it, both indoors and outdoors.

Sowing by USDA Hardiness Zone

*When direct sowing outdoors, your soil should be well-drained, fertile, and at least 60°. If you live in a cool region, you can cover the seeds with row cover during germination to add an extra layer of warmth. 

If you do not know your zone, refer to the USDA Hardiness Zone Map and plan your garden accordingly. The Farmers’ Almanac also has a convenient frost calculator based on your zip code! 

Cold Climates (Zones 3a – 6b)

Start seeds inside a greenhouse or use a heat mat and a sunny windowsill in your home. Let them grow for about six weeks until well-established. Do not plant them outdoors until the risk of frost has passed (around mid-May) and the soil has warmed to at least 50°. 

Pro Tip: Plant them alongside tomatoes for added protection from wind and additional heat. Use row cover or frost blankets during cooler nights as needed.

Mild Climates (Zones 7a – 9b)

Starting in March, you can start basil indoors if you grow in zones 7a – 9b. Seeds will germinate best at warmer temperatures, so although you can directly sow them in the ground, you risk spotty germination or failure to thrive if you get a sudden burst of cold weather.

Your best bet is to start them indoors in a sunny window, on a heat mat, or in a greenhouse. In zones 9a and 9b, your growing season will cover most, but not quite all of the year!

Warm Climates (Zones 10a – 11b)

With no fear of frost, you can sow basil in both spring and fall for a continuous supply of basil. However, caution should be taken during the year’s hottest months as basil can also be very sensitive to extreme sun exposure and extended dry periods. 

Basil is considered an annual, even when grown in warm climates, so it’s best to sow seeds in late fall – early spring to start fresh with new plants each season.

Colder Climates 

Basil is a heat-loving crop and does best outdoors when temperatures are 50° – 80°. Below 45-50° will certainly not kill basil, but it is not ideal for a long period of time.

Plants will not survive a frost and will start to show damage from low temperatures through black spots on the leaves, making them unmarketable and not ideal for culinary uses. The leaves may also begin to wilt or curl. It will likely not bounce back after this point, so take good care of them early and late in the season.  

Frost Protection

Here are a few things you can do when nighttime lows are still chilly that will help keep them warm and cozy:

• Place your plants near other established plants that are giving off heat.
• Use a frost blanket or row cover secured tightly so the wind does not come through.
• Mulch your plants to help keep the soil warm.
• Bring your plants inside if using a pot or grow bag.
• Be sure your soil is well-drained and there is no standing water.
• Excessive moisture will lower the soil temperature and could ultimately allow the roots to rot.

Mild Climates

You’ll have to be a bit more cautious in late spring planting basil outside. In many mild climates across mid-America, while daytime temperatures can increase to almost summerlike weather, nighttime lows usually remain in the 30s and can be somewhat unpredictable.

Most often, across the Northeast and throughout the Midwest, the chance of frost will run through mid-late May, so be certain you are in the clear before planting your vulnerable basil plants outdoors. 

Grow bags and pots are a great option for “hardening off” your basil plants during these unpredictable months. “Hardening off” is a term used that means getting them used to direct sunlight, even some rain and wind, with the ability to bring them back indoors at night until you can safely plant them out.

This decreases the risk of transplant shock when they are eventually planted out into the ground. During times of uncertainty,  you can follow some of the tips above for growing in a cold climate to protect your basil from the cold. 

Warm Climates

Even though basil loves heat, it can be known to struggle a bit when it receives too much sun and heat with prolonged drought conditions. To combat this, plant it out in an area where your basil receives some late afternoon shade.

If you don’t have an area that receives shade, you can use shade cloth, create shade with row cover, plant inside a tunnel or greenhouse or move your grow bag or pot to a different spot in your garden (if not planted in the ground, that is). 

Another important thing to note is that basil prefers to be watered regularly, and it’s best if it is deep root watered, meaning by soaker hoses or drip lines versus overhead sprinklers. 

Pro Tip: Basil grows exceptionally well alongside tomatoes which are typically watered every 1-3 days and also prefer to be watered at the root level so planting them together just makes sense!

Basil should receive at least 1 inch of rain per week, so if there is no rain in the forecast and it’s a particularly sunny week, be sure you water your plants so they continue growing and producing. 

Growing Basil in Containers

If you are starting out as a backyard grower or do not have a ton of space, basil is the perfect crop to plant in grow bags or pots.

You can grow herbs, including basil, in grow bags in any climate, but they are especially handy if you live in a colder climate. It performs well, and the bags make it easier to transport in and out of a protected space when the risk of frost arises. 

Keep a close eye on the soil moisture when growing in pots or grow bags. Plants do not have the ability to reach deeper into the soil for moisture like they would when planted in the ground, so it’s up to you to keep them from drying out. 

Pro Tip: There are compact versions of some varieties that make container growing even easier!