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When to Start Basil Seeds

Dates to start basil indoors, harden off and plant out for your ZIP code or zone.

Tomato and pepper seedlings in trays under an LED grow light

Basil planting dates by zone

At the average last frost date for each USDA half-zone (the median across its ZIP codes, NOAA 1991 to 2020 normals). Enter your ZIP code below for your own dates.

ZoneLast frostStart indoorsTransplantSow outdoors
3aMay 28Apr 16 to Apr 30May 28May 28
3bMay 17Apr 5 to Apr 19May 17May 17
4aMay 13Apr 1 to Apr 15May 13May 13
4bMay 8Mar 27 to Apr 10May 8May 8
5aMay 4Mar 23 to Apr 6May 4May 4
5bMay 1Mar 20 to Apr 3May 1May 1
6aApr 29Mar 18 to Apr 1Apr 29Apr 29
6bApr 23Mar 12 to Mar 26Apr 23Apr 23
7aApr 16Mar 5 to Mar 19Apr 16Apr 16
7bApr 6Feb 23 to Mar 9Apr 6Apr 6
8aMar 29Feb 15 to Mar 1Mar 29Mar 29
8bMar 18Feb 4 to Feb 18Mar 18Mar 18
9aMar 3Jan 20 to Feb 3Mar 3Mar 3
9bFeb 2Dec 22 to Jan 5Feb 2Feb 2
10aJan 16Dec 5 to Dec 19Jan 16Jan 16
10brareby seasonby seasonby season
Your location

Zone medians. Your ZIP code gives the dates of your nearest weather station.

Frost risk

Half of years still get a frost after the spring date, and half get the first fall frost before the fall date.

Frost dates at three risk levels
AverageSaferSafest
Last spring frostApr 23Apr 30May 9
First fall frostOct 22Oct 16Oct 7
Crops (1 selected)

Start your first seeds indoors

Mar 12basil

Average frost dates: last Apr 23, first Oct 22 (zone 6b).
Season
Spring seed starting schedule
CropStart indoorsHarden offTransplantSow outdoorsNotes
BasilVery tenderMar 12 to Mar 26Apr 2 to Apr 22Apr 23Apr 23Indoors 4 to 6 wk before last frost. Transplant at last frost. Sow outdoors at last frost. Sprouts in 5 to 14 days, best at 75 to 85°F soil. Pot up at the first true leaves.

How to start seeds indoors

Light
Give seedlings 14 to 18 hours of light a day on a timer, with fluorescent or LED fixtures 2 to 6 in above the leaves. Raise the lights as the plants grow.
Clemson HGIC: 16 to 18 hours, tubes 2 to 4 in above. UMD Extension: 14 to 16 hours, 2 to 6 in.
Seed starting mix
Use a sterile, soilless mix, never garden soil. To mix your own, combine equal parts by volume of fine pine bark, sphagnum peat moss and perlite.
NC State Extension Gardener Handbook; Clemson HGIC.
Sowing and warmth
Sow two or three seeds per cell and keep the strongest seedling. A mix temperature of 65 to 75°F germinates most vegetables; after they sprout, 55 to 60°F nights and 65 to 70°F days keep them stocky.
UMD Extension.
Potting up
Move seedlings into larger pots shortly after the first true leaves appear, while they are small and recover quickly.
UMD Extension; Clemson HGIC (one or two sets of true leaves).
Hardening off
Start two to three weeks before transplanting, once plants are about 3 in tall: set them outdoors by day, bring them in before sundown, and give them more direct sun each day. Skip days below 45°F or with strong wind.
Clemson HGIC: 2 to 3 weeks. NC State: at least 2 weeks, not below 45°F.

When to start basil seeds

Start basil seeds indoors 4 to 6 weeks before your last spring frost, and set the plants out, or sow seed outdoors, on or after the last frost date. Clemson Extension sows basil indoors four to six weeks ahead of the outdoor planting time, and Utah State University Extension plants seeds or transplants only after the last frost. The table above applies that rule to every USDA zone's average last frost, from NOAA's 1991 to 2020 normals.

Basil dates in three zones

Zone (average last frost)Start indoorsHarden offTransplant or sow outside
5b (May 1)Mar 20 to Apr 3Apr 10 to Apr 30May 1
7a (Apr 16)Mar 5 to Mar 19Mar 26 to Apr 15Apr 16
9a (Mar 3)Jan 20 to Feb 3Feb 10 to Mar 2Mar 3

Hardening off takes the two to three weeks before transplanting, as Clemson's seed starting guide recommends. Enter your ZIP code in the planner above for your own frost date instead of the zone average.

Wait for warm nights, not just the frost date

The last frost date is the earliest basil can go out, not always the best day. Clemson holds basil back until nights stay above 50 °F and daytime temperatures are consistently in the 70s, and Maryland Extension notes basil does not tolerate chilly weather. If your seedlings are ready and the nights are still cold, keep them in their pots a little longer.

The planner's Safer or Safest frost setting moves the dates later, a cautious choice for a crop this sensitive to cold.

Germination

Basil seed is small. Clemson plants it 1/4 inch deep, and Utah State sows 1/8 inch deep and covers it lightly. Germination depends on warmth: Clemson expects seedlings in 5 to 10 days at 70 °F, and Utah State gives about 10 to 14 days with soil at 75 to 85 °F. Once seedlings are up, Utah State thins them to 3 to 4 inches apart, then keeps thinning until plants stand 12 inches apart in the garden.

Sow again for a steady supply

Utah State notes that planting basil every other week helps prevent early flowering. After the first indoor batch goes out at the last frost, direct sow a short row every two weeks. For the number of sowings that fit your season, use the succession planting planner.

How many to start

Utah State plans 5 to 10 plants per person for fresh use and another 5 to 10 per person to dry or freeze. Space the plants out with the basil spacing calculator. For the rest of your seedlings, the seed starting calculator builds a full indoor schedule.