When to Plant Basil: Soil Temperature, Frost Dates and Starting Seeds

Basil is the herb that most often goes in too early. A sunny week in spring tempts gardeners to plant, then a cold night damages the leaves or stalls the plants for weeks. Waiting for warm soil and warm nights usually gives you bigger plants sooner. This guide covers timing; for companions and care, see what to plant with basil.

Dates by last frost

The table counts from your average last spring frost. The indoor column is Clemson's 4 to 6 weeks before planting out; the outdoor column follows our planting calendar, which puts basil out from the frost date to about two weeks after it. Treat the outdoor dates as the earliest, and check the soil and the night forecast first.

Regional examples: Utah State says basil transplants usually go out in mid to late May in Utah. University of Minnesota Extension says to direct sow after all danger of frost has passed.

Wait for warm soil and warm nights

Extension sources set the bar a little differently, but they agree basil wants real warmth:

• Soil: at least 60°F at planting (Penn State, Illinois). Utah State says seeds germinate best in soil of 75 to 85°F.
• Nights: Clemson says not to transplant until days are consistently in the 70s and nights are above 50°F; UF/IFAS says Florida gardeners should wait until nights are above 55°F.
• Cold damage: Illinois says cold can damage or blacken the leaves at 50°F, and Penn State and UF say temperatures below 40°F discolor or blacken them.

If a cold night arrives after planting, Clemson suggests covering the plants.

Starting basil from seed

Sow again in summer

One spring planting can last all summer if you keep pinching off the flowers, but a second sowing in early summer gives you fresh, leafy plants for late summer and fall. Illinois suggests indoor windowsill sowings every two weeks for a steady supply. Utah State notes that heat and water stress push basil to flower, so a well-watered, mulched bed stays productive longer.

Downy mildew is another reason to sow again. Maryland Extension says that if the disease kills plants early in the season, you can sow fresh seed, and it lists downy mildew-resistant varieties such as 'Obsession', 'Devotion', 'Prospera' and 'Amazel'. Because Maryland says leaves are ready about six weeks after planting, sow any late batch at least six weeks before your first fall frost.

The end of the season

Basil won't survive frost. Penn State advises harvesting all of it before the cold arrives, and Illinois notes that leaves can be damaged at 50°F, so watch the forecast in early fall and pick heavily when nights start dropping into the 40s. Our what to plant in fall guide covers what can follow it in the bed.

Texas, Florida and hot-summer areas

In Florida, UF/IFAS says basil can be planted in early spring or in fall, waiting in spring until nights are above 55°F. In hot-summer areas generally, spring and early fall plantings tend to be the most productive, because heat and water stress push the plants to flower (USU). For the crops basil grows alongside, see when to plant tomatoes and when to plant peppers.

Frequently asked questions

When should I plant basil outside?

After your last frost, once the soil has warmed to at least 60°F (Penn State, Illinois). Clemson says to wait until days are consistently in the 70s and nights are above 50°F.

When should I start basil seeds indoors?

About 4 to 6 weeks before you plan to plant out (Clemson). Penn State says about 6 weeks before the last frost, and UMN 6 to 8 weeks.

What temperature is too cold for basil?

Illinois says cold can damage or blacken the leaves at 50°F, and Penn State and UF say temperatures below 40°F discolor them. Basil won't survive frost.

Can I plant basil in May?

Often, yes. Utah State says transplants usually go out in mid to late May in Utah. Anywhere, check that your last frost has passed and the soil is at least 60°F.

Can I plant basil seeds directly in the garden?

Yes. UMN says to direct sow after all danger of frost has passed; seeds sprout in about 5 to 14 days depending on soil warmth (UMN, USU).

How long does basil take to grow?

Maryland Extension says leaves are ready to harvest about six weeks after planting. Illinois says transplants take three to four weeks to start producing.