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When to Start Marigold Seeds

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

Tomato and pepper seedlings in trays under an LED grow light

Marigold 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 12marigold

Average frost dates: last Apr 23, first Oct 22 (zone 6b).
Season
Spring seed starting schedule
CropStart indoorsHarden offTransplantSow outdoorsNotes
MarigoldTenderMar 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 7 days, best at 70 to 75°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 marigold seeds

Clemson's Home and Garden Information Center starts marigold seeds indoors 4 to 6 weeks before planting time and sets the plants out after the last spring frost. You can also sow directly in the garden on the same date, once the soil has warmed and the danger of frost has passed.

ZoneAverage last frostStart indoors (French)Harden offTransplant or sow outdoors
5bMay 1Mar 20 to Apr 3Apr 10 to Apr 30May 1
7aApr 16Mar 5 to Mar 19Mar 26 to Apr 15Apr 16
9aMar 3Jan 20 to Feb 3Feb 10 to Mar 2Mar 3

Frost dates are the median across each half-zone's ZIP codes from NOAA's 1991 to 2020 normals, so a frost still comes later in half of years. The harden off window is the two to three weeks Clemson recommends for moving seedlings outdoors gradually.

African marigolds need a longer start

The table and the planner use the 4 to 6 weeks that fit French marigolds. Clemson starts African marigolds, which grow up to 36 inches tall, 8 weeks before planting out. At the average last frost that means sowing around:

  • Mar 6 in zone 5b
  • Feb 19 in zone 7a
  • Jan 6 in zone 9a

If you grow both, sow the African marigolds first and the French ones two to four weeks later, and harden them off together.

Germination

Clemson sows seed about 1/4 inch deep and keeps it at 70 to 75 °F; at that temperature seedlings appear in 5 to 7 days. That is ordinary room warmth, so no heat mat is needed. Outdoors, sow at the same depth; Clemson gives the same 5 to 7 days for direct-sown seed.

Planting out

Set French marigolds 8 to 10 inches apart and African marigolds 12 to 16 inches, in full sun with at least 6 hours a day and well-drained soil. The marigold spacing calculator shows how many fit your bed or edging row, and so how many seeds to start.

Once they bloom, Clemson advises removing the old flowers as they fade to keep new ones coming.

Using the planner

Enter your ZIP code above to replace the zone averages with your own frost dates. Choose the Safer or Safest frost risk to push the transplant date later if frosts often come late where you live. Add vegetables and other flowers to see one combined sowing calendar, or use the seed starting calculator for the whole garden.