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Historical frost averages plus extension guidance, not a forecast. Check the forecast and soil temperature before planting.
Start basil seeds indoors 4–6 weeks before your last spring frost, then plant out 1–3 weeks after that date. You can also sow basil straight into the garden 1–3 weeks after the last frost. Basil is very sensitive to cold, so wait until nights stay above about 50°F.
- Frost tolerance
- Very tender: no frost
- Soil temperature
- Warm soil, about 70°F, for quick sprouting
- Days to harvest
- Leaves in 3–4 weeks from transplant
The rule we use
- Start seeds indoors: 4–6 weeks before the last spring frost
- Plant out: 1–3 weeks after the last spring frost
- Sow outdoors: 1–3 weeks after the last spring frost
Starting basil
Basil seed sprouts quickly in warm conditions, often in 5–10 days. Sow it shallowly, about ⅛–¼ inch deep, and keep the tray warm. Seedlings need bright light; on a dim windowsill they flop over. Basil grows fast, so 4–6 weeks indoors is plenty.
In warm areas, direct sowing works well once the soil has warmed. Sow a few seeds every few weeks through early summer for a steady supply of young plants.
Cold is basil's biggest enemy
Basil is one of the most cold-sensitive plants in the garden. Frost kills it outright, and nights below about 50°F can blacken the leaves and stop growth for weeks. Don't rush it outside; a plant set out in warm weather quickly overtakes one planted early.
In fall, basil is usually the first thing to die. Harvest heavily when nights start dropping into the 40s, or cover the plants.
Pinch for bushy plants
When a plant has 3–4 pairs of leaves, pinch out the top just above a pair of leaves. Two new shoots grow from that point, and the plant gets bushier. Keep picking from the tips through summer, and pinch off flower spikes as they appear: once basil flowers, leaf production slows and the flavor changes.
Basil also grows well in pots and indoor gardens, which lets you keep a supply going after frost.
Seeds and supplies for basil
- Basil seeds at True Leaf Market
- Park Seed for seeds and young plants.
- Click & Grow indoor gardens grow herbs and greens on a counter all year.
- LED grow lights stop seedlings stretching toward a window.
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Questions about planting basil
When can I put basil outside?
Once nights stay above about 50°F, which is usually 1–3 weeks after your last spring frost. Enter your ZIP above for dates.
Can basil survive a frost?
No. Even a light frost kills basil, and cold nights above freezing can damage the leaves. Cover or harvest it before a cold night.
Should I start basil indoors or sow it outside?
Either works. Starting indoors gives you an earlier harvest. Direct sowing is simple once the soil is warm, especially in the South.
Why are my basil leaves turning black?
Usually cold. Nights in the 40s or a cold wind can blacken leaves. It can also be a disease called downy mildew, which causes yellowing with gray fuzz under the leaves.
Sources
- Central North Carolina Planting Calendar for Annual Vegetables, Fruits, and Herbs, NC State Extension
- Extension Gardener Handbook, Ch. 16: Vegetable Gardening, NC State Extension
- Frost dates: NOAA NCEI U.S. Climate Normals 1991–2020 (doi:10.25921/4ek7-fk11)