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When to Start Seeds Indoors in Zone 5

Start indoor, transplant, direct sow and fall dates for every crop in zones 5a and 5b, with their frost dates.

Tomato and pepper seedlings in trays under an LED grow light

Zone 5 frost dates

Median last spring and first fall frost dates for zone 5
Half-zoneLast spring frostFirst fall frostFrost-free days
AverageSaferSafestAverageSaferSafest
5a (-20 to -15°F)May 4May 9May 17Oct 4Sep 30Sep 22153
5b (-15 to -10°F)May 1May 7May 16Oct 10Oct 4Sep 27161

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 5a

Counted from the average last frost, May 4, and the average first frost, Oct 4.

Planting dates for zone 5a at average frost dates
CropStart indoorsTransplantSow outdoorsFall sowing
BasilMar 23 to Apr 6May 4May 4·
Beet··Apr 20 to May 4by Aug 9
BroccoliMar 23 to Apr 6Apr 13 to Apr 20Apr 13 to Apr 20·
Brussels Sprouts···Jun 7
CabbageFeb 23 to Mar 9Apr 13 to Apr 20Apr 13 to Apr 20·
Cantaloupe··May 11 to May 18·
Carrot··Apr 13 to Apr 20·
CauliflowerMar 2 to Mar 16Apr 20 to Apr 27Apr 20 to Apr 27·
CilantroMar 23 to Apr 6May 4May 4·
Collard Greens···Jul 5
Cucumber··May 4·
Dill··Apr 20 to Apr 27·
EggplantMar 23 to Apr 6May 18··
Green Beans··Apr 27 to May 4·
KaleFeb 16 to Mar 2Mar 30 to Apr 6Mar 30 to Apr 6Jul 5
LeekFeb 9 to Feb 23···
LettuceMar 23 to Mar 30May 4Apr 13 to Apr 20·
MarigoldMar 23 to Apr 6May 4May 4·
OnionMar 9 to Mar 23Apr 6 to Apr 20··
ParsleyMar 23May 4May 4·
Peas··Apr 6 to Apr 20Aug 2 to Aug 9
PepperMar 9 to Mar 23May 18··
Potato··Apr 13 to Apr 20·
Pumpkin··May 18·
Radish··Apr 6 to Apr 20·
SpinachMar 23 to Mar 30May 4Apr 6 to Apr 13·
Squash··May 4·
Sunflower··May 4·
Sweet Corn··May 4·
Swiss ChardMar 23 to Mar 30May 4Apr 6 to Apr 13·
TomatoMar 9 to Mar 23May 18··
Watermelon··May 11 to May 18·
ZinniaApr 6May 4May 4·
Zucchini··May 4·

When to start seeds in zone 5b

Counted from the average last frost, May 1, and the average first frost, Oct 10.

Planting dates for zone 5b at average frost dates
CropStart indoorsTransplantSow outdoorsFall sowing
BasilMar 20 to Apr 3May 1May 1·
Beet··Apr 17 to May 1by Aug 15
BroccoliMar 20 to Apr 3Apr 10 to Apr 17Apr 10 to Apr 17·
Brussels Sprouts···Jun 13
CabbageFeb 20 to Mar 6Apr 10 to Apr 17Apr 10 to Apr 17·
Cantaloupe··May 8 to May 15·
Carrot··Apr 10 to Apr 17·
CauliflowerFeb 27 to Mar 13Apr 17 to Apr 24Apr 17 to Apr 24·
CilantroMar 20 to Apr 3May 1May 1·
Collard Greens···Jul 11
Cucumber··May 1·
Dill··Apr 17 to Apr 24·
EggplantMar 20 to Apr 3May 15··
Green Beans··Apr 24 to May 1·
KaleFeb 13 to Feb 27Mar 27 to Apr 3Mar 27 to Apr 3Jul 11
LeekFeb 6 to Feb 20···
LettuceMar 20 to Mar 27May 1Apr 10 to Apr 17·
MarigoldMar 20 to Apr 3May 1May 1·
OnionMar 6 to Mar 20Apr 3 to Apr 17··
ParsleyMar 20May 1May 1·
Peas··Apr 3 to Apr 17Aug 8 to Aug 15
PepperMar 6 to Mar 20May 15··
Potato··Apr 10 to Apr 17·
Pumpkin··May 15·
Radish··Apr 3 to Apr 17·
SpinachMar 20 to Mar 27May 1Apr 3 to Apr 10·
Squash··May 1·
Sunflower··May 1·
Sweet Corn··May 1·
Swiss ChardMar 20 to Mar 27May 1Apr 3 to Apr 10·
TomatoMar 6 to Mar 20May 15··
Watermelon··May 8 to May 15·
ZinniaApr 3May 1May 1·
Zucchini··May 1·

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 frostMay 4May 9May 17
First fall frostOct 4Sep 30Sep 22
Crops (8 selected)

Start your first seeds indoors

Mar 9onion, pepper, tomato

Average frost dates: last May 4, first Oct 4 (zone 5a).
Season
Spring seed starting schedule
CropStart indoorsHarden offTransplantSow outdoorsNotes
BasilVery tenderMar 23 to Apr 6Apr 13 to May 3May 4May 4Indoors 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 23 to Apr 6Apr 6 to Apr 12Apr 13 to Apr 20Apr 13 to Apr 20Indoors 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···May 4Sow outdoors at last frost. Sprouts in 6 to 10 days, best at 60 to 95°F soil.
LettuceHardyMar 23 to Mar 30Apr 13 to May 3May 4Apr 13 to Apr 20Indoors 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 9 to Mar 23Mar 23 to Apr 5Apr 6 to Apr 20·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 9 to Mar 23Apr 27 to May 17May 18·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···May 4Sow outdoors at last frost. Sprouts in 3 to 12 days, best at 70 to 95°F soil.
TomatoVery tenderMar 9 to Mar 23Apr 27 to May 17May 18·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 5 frost dates

Zone 5 winters reach -20 to -10°F. It is one of the most gardened zones, with 2,280 ZIP codes in 5a and 2,592 in 5b in the data. The NOAA 1991 to 2020 medians are:

  • Zone 5a: average last spring frost May 4, first fall frost Oct 4, and 153 frost-free days.
  • Zone 5b: average last spring frost May 1, first fall frost Oct 10, and 161 frost-free days.

5b gains most of its extra week in fall: its first frost comes 6 days later, while its last frost is only 3 days earlier. For seed starting, which counts from the spring date, the two halves are almost the same calendar.

Start dates for zone 5

Start indoors = last frost date − weeks indoors

  • Tomatoes and peppers (6 to 8 weeks) are sown Mar 9 to Mar 23 in 5a and Mar 6 to Mar 20 in 5b. They are transplanted 2 weeks after the frost, on May 18 in 5a and May 15 in 5b.
  • Leeks (10 to 12 weeks) start Feb 9 to Feb 23 in 5a.
  • Kale (9 to 11 weeks) starts Feb 16 to Mar 2.
  • Peas are sown straight into the bed from Apr 6 to Apr 20.

A city can beat its zone by a week or more

The zone median is a middle value across thousands of ZIP codes, and one ZIP can land well away from it. Minneapolis ZIP 55401 is in zone 5a, but its station, Lower St Anthony Falls, has an average last frost of Apr 23. That is 11 days before the 5a median of May 4, and it puts tomato sowing at Feb 26 to Mar 12 instead of Mar 9 to Mar 23. Hardiness zones measure the coldest winter night, not the date of the last spring frost, so a warm city center and a cold hollow can share a zone and still differ by weeks. If you know your ZIP code, use it in the seed starting calculator.

Which risk level to plan with

In 5a:

  • The safer last frost is May 9 and the safest is May 17.
  • For tomatoes, that moves transplanting to May 23 at the safer setting and May 31 at the safest.

The season is long enough either way. At the safest dates, peppers set out on May 31 still have 114 days before the Sep 22 first frost, well above the 70 to 85 they need. So the cost of playing safe is only a later first harvest. A middle course is to start seeds from the average date and hold transplants back to the safer date. The seedlings then spend about a week longer in their pots.

Fall crops in zone 5

Counting back from the average first frost:

Crop5a5b
Brussels sproutsby Jun 7by Jun 13
Kale and collardsby Jul 5by Jul 11
Fall peasAug 2 to Aug 9Aug 8 to Aug 15
Last beet sowingAug 9Aug 15

Nearby zones

Compare zone 4 and zone 6, or switch the planner below between 5a and 5b.