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When to Start Seeds Indoors in Zone 6

Start indoor, transplant, direct sow and fall dates for every crop in zones 6a and 6b, with their frost dates.

Tomato and pepper seedlings in trays under an LED grow light

Zone 6 frost dates

Median last spring and first fall frost dates for zone 6
Half-zoneLast spring frostFirst fall frostFrost-free days
AverageSaferSafestAverageSaferSafest
6a (-10 to -5°F)Apr 29May 4May 14Oct 16Oct 10Oct 1170
6b (-5 to 0°F)Apr 23Apr 30May 9Oct 22Oct 16Oct 7181

Medians across the ZIP codes in each half-zone, NOAA 1991 to 2020 climate normals. Average: half of years get frost past the date. Safer: 3 years in 10 (the Almanac's date). Safest: 1 year in 10.

When to start seeds in zone 6a

Counted from the average last frost, Apr 29, and the average first frost, Oct 16.

Planting dates for zone 6a at average frost dates
CropStart indoorsTransplantSow outdoorsFall sowing
BasilMar 18 to Apr 1Apr 29Apr 29·
Beet··Apr 15 to Apr 29by Aug 21
BroccoliMar 18 to Apr 1Apr 8 to Apr 15Apr 8 to Apr 15·
Brussels Sprouts···Jun 19
CabbageFeb 18 to Mar 4Apr 8 to Apr 15Apr 8 to Apr 15·
Cantaloupe··May 6 to May 13·
Carrot··Apr 8 to Apr 15·
CauliflowerFeb 25 to Mar 11Apr 15 to Apr 22Apr 15 to Apr 22·
CilantroMar 18 to Apr 1Apr 29Apr 29·
Collard Greens···Jul 17
Cucumber··Apr 29·
Dill··Apr 15 to Apr 22·
EggplantMar 18 to Apr 1May 13··
Green Beans··Apr 22 to Apr 29·
KaleFeb 11 to Feb 25Mar 25 to Apr 1Mar 25 to Apr 1Jul 17
LeekFeb 4 to Feb 18···
LettuceMar 18 to Mar 25Apr 29Apr 8 to Apr 15·
MarigoldMar 18 to Apr 1Apr 29Apr 29·
OnionMar 4 to Mar 18Apr 1 to Apr 15··
ParsleyMar 18Apr 29Apr 29·
Peas··Apr 1 to Apr 15Aug 14 to Aug 21
PepperMar 4 to Mar 18May 13··
Potato··Apr 8 to Apr 15·
Pumpkin··May 13·
Radish··Apr 1 to Apr 15·
SpinachMar 18 to Mar 25Apr 29Apr 1 to Apr 8·
Squash··Apr 29·
Sunflower··Apr 29·
Sweet Corn··Apr 29·
Swiss ChardMar 18 to Mar 25Apr 29Apr 1 to Apr 8·
TomatoMar 4 to Mar 18May 13··
Watermelon··May 6 to May 13·
ZinniaApr 1Apr 29Apr 29·
Zucchini··Apr 29·

When to start seeds in zone 6b

Counted from the average last frost, Apr 23, and the average first frost, Oct 22.

Planting dates for zone 6b at average frost dates
CropStart indoorsTransplantSow outdoorsFall sowing
BasilMar 12 to Mar 26Apr 23Apr 23·
Beet··Apr 9 to Apr 23by Aug 27
BroccoliMar 12 to Mar 26Apr 2 to Apr 9Apr 2 to Apr 9·
Brussels Sprouts···Jun 25
CabbageFeb 12 to Feb 26Apr 2 to Apr 9Apr 2 to Apr 9·
Cantaloupe··Apr 30 to May 7·
Carrot··Apr 2 to Apr 9·
CauliflowerFeb 19 to Mar 5Apr 9 to Apr 16Apr 9 to Apr 16·
CilantroMar 12 to Mar 26Apr 23Apr 23·
Collard Greens···Jul 23
Cucumber··Apr 23·
Dill··Apr 9 to Apr 16·
EggplantMar 12 to Mar 26May 7··
Green Beans··Apr 16 to Apr 23·
KaleFeb 5 to Feb 19Mar 19 to Mar 26Mar 19 to Mar 26Jul 23
LeekJan 29 to Feb 12···
LettuceMar 12 to Mar 19Apr 23Apr 2 to Apr 9·
MarigoldMar 12 to Mar 26Apr 23Apr 23·
OnionFeb 26 to Mar 12Mar 26 to Apr 9··
ParsleyMar 12Apr 23Apr 23·
Peas··Mar 26 to Apr 9Aug 20 to Aug 27
PepperFeb 26 to Mar 12May 7··
Potato··Apr 2 to Apr 9·
Pumpkin··May 7·
Radish··Mar 26 to Apr 9·
SpinachMar 12 to Mar 19Apr 23Mar 26 to Apr 2·
Squash··Apr 23·
Sunflower··Apr 23·
Sweet Corn··Apr 23·
Swiss ChardMar 12 to Mar 19Apr 23Mar 26 to Apr 2·
TomatoFeb 26 to Mar 12May 7··
Watermelon··Apr 30 to May 7·
ZinniaMar 26Apr 23Apr 23·
Zucchini··Apr 23·

Your own schedule

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 29May 4May 14
First fall frostOct 16Oct 10Oct 1
Crops (8 selected)

Start your first seeds indoors

Mar 4onion, pepper, tomato

Average frost dates: last Apr 29, first Oct 16 (zone 6a).
Season
Spring seed starting schedule
CropStart indoorsHarden offTransplantSow outdoorsNotes
BasilVery tenderMar 18 to Apr 1Apr 8 to Apr 28Apr 29Apr 29Indoors 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.
BroccoliHardyMar 18 to Apr 1Apr 1 to Apr 7Apr 8 to Apr 15Apr 8 to Apr 15Indoors 4 to 6 wk before last frost. Transplant 2 to 3 wk before last frost. Sow outdoors 2 to 3 wk before last frost. Sprouts in 3 to 10 days, best at 80°F soil. Pot up at the first true leaves. The published dates leave little time indoors: sow at the early end.
CucumberTender···Apr 29Sow outdoors at last frost. Sprouts in 6 to 10 days, best at 60 to 95°F soil.
LettuceHardyMar 18 to Mar 25Apr 8 to Apr 28Apr 29Apr 8 to Apr 15Indoors 5 to 6 wk before last frost. Transplant at last frost. Sow outdoors 2 to 3 wk before last frost. Sprouts in 4 to 10 days, best at 40 to 80°F soil. Pot up at the first true leaves.
OnionHardyMar 4 to Mar 18Mar 18 to Mar 31Apr 1 to Apr 15·Indoors 6 to 8 wk before last frost. Transplant 2 to 4 wk before last frost. Sprouts in 7 to 12 days, best at 50 to 95°F soil. Pot up at the first true leaves.
PepperVery tenderMar 4 to Mar 18Apr 22 to May 12May 13·Indoors 6 to 8 wk before last frost. Transplant 2 wk after last frost. Sprouts in 10 to 20 days, best at 65 to 95°F soil. Pot up at the first true leaves.
SquashTender···Apr 29Sow outdoors at last frost. Sprouts in 3 to 12 days, best at 70 to 95°F soil.
TomatoVery tenderMar 4 to Mar 18Apr 22 to May 12May 13·Indoors 6 to 8 wk before last frost. Transplant 2 wk after last frost. Sprouts in 6 to 14 days, best at 60 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.

Zone 6 frost dates

Zone 6 is the biggest zone in the data: 4,574 ZIP codes in 6a and 4,570 in 6b, with winter lows of -10 to 0°F. The NOAA 1991 to 2020 medians are:

Last frost (average)SaferSafestFirst frost (average)Frost-free days
6aApr 29May 4May 14Oct 16170
6bApr 23Apr 30May 9Oct 22181

6b runs about 6 days ahead of 6a in spring and 6 days behind it in fall. Over a season that adds up to 11 more frost-free days.

Zone 6 seed starting calendar

Every start date is the last frost minus the crop's weeks indoors:

Start indoors = last frost date − weeks indoors

Month by month, at average dates:

  • Late January to February: leeks (10 to 12 weeks) from Jan 29 in 6b and Feb 4 in 6a, then kale and cabbage from early February.
  • Late February to mid-March: tomatoes, peppers and onions, all at 6 to 8 weeks. Sow them Feb 26 to Mar 12 in 6b and Mar 4 to Mar 18 in 6a.
  • Mid-March to early April: broccoli, lettuce and basil, at 4 to 6 weeks, starting Mar 12 in 6b and Mar 18 in 6a.
  • Late March to mid-April: onion transplants go out 2 to 4 weeks before the frost, and peas are sown outdoors (Mar 26 to Apr 9 in 6b, Apr 1 to Apr 15 in 6a).
  • Late April: cucumbers and squash are sown outdoors on the frost date itself: Apr 23 in 6b and Apr 29 in 6a.
  • May: tomatoes and peppers go out 2 weeks after the frost, on May 7 in 6b and May 13 in 6a. Start hardening them off 2 to 3 weeks before that, as Clemson Extension advises.

Choosing a frost date

A 6a gardener who plans with the safest date (May 14) transplants tomatoes on May 28, a full two weeks after the average plan. The season is long enough that nothing is lost but time. At the safest dates, peppers still have 126 days in 6a before the first frost, against the 70 to 85 they need. The calculator flags no crop in zone 6 as too slow at any risk level.

Local dates can still land well away from the median. Denver ZIP 80202 is in zone 6a, and its station at 5,228 ft has an average last frost of Apr 30, right on the 6a median. Other 6a ZIP codes can differ by more, and the seed starting calculator shows the station behind yours.

Fall sowing in zone 6

The first frost comes in mid to late October, which makes zone 6 good for a second, cool-season crop:

Crop6a6b
Brussels sproutsby Jun 19by Jun 25
Kale and collardsby Jul 17by Jul 23
Fall peasAug 14 to Aug 21Aug 20 to Aug 27
Last beet sowingAug 21Aug 27

Related calendars

See zone 5 and zone 7 if you sit near a boundary. Once you know what to grow, the plant spacing calculator tells you how many transplants to raise.