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When to Plant Zucchini Seeds

The dates to sow zucchini outdoors for your ZIP code or zone, from NOAA frost dates.

Tomato and pepper seedlings in trays under an LED grow light

Zucchini 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 frostSow outdoors
3aMay 28May 28
3bMay 17May 17
4aMay 13May 13
4bMay 8May 8
5aMay 4May 4
5bMay 1May 1
6aApr 29Apr 29
6bApr 23Apr 23
7aApr 16Apr 16
7bApr 6Apr 6
8aMar 29Mar 29
8bMar 18Mar 18
9aMar 3Mar 3
9bFeb 2Feb 2
10aJan 16Jan 16
10brareby 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)

First job: sow seeds outdoors

Apr 23zucchini

Average frost dates: last Apr 23, first Oct 22 (zone 6b).
Season
Spring seed starting schedule
CropSow outdoorsNotes
ZucchiniTenderApr 23Sow outdoors at last frost. Sprouts in 3 to 12 days, best at 70 to 95°F soil.

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 plant zucchini seeds

Sow zucchini outdoors on your average last frost date, once the soil is at least 65°F. Colorado State University Extension and Utah State University Extension both time it with the frost date, and the seed goes in 1 to 1 1/2 inches deep. Oregon State University's germination table gives 70 to 95°F as the best soil range; there the seed comes up in 3 to 12 days.

Zucchini is a direct sown crop in these sources, so the planner above gives a Sow outdoors date for your ZIP code rather than an indoor start.

Example dates by zone

At the average (50%) frost dates for each half-zone, from NOAA's 1991 to 2020 normals:

ZoneSow outdoorsFirst fall frostDays until that frost
4bMay 8Oct 1146
5bMay 1Oct 10162
7aApr 16Oct 25192
9aMar 3Nov 25267

The sowing date is the last frost date itself. Colorado State counts about 50 days from seeding to the first zucchini, so even the 146 days of zone 4b leave room for two or three sowings.

Sow again for a steady harvest

Johnny's Selected Seeds suggests a new sowing every 2 to 3 weeks. Virginia Cooperative Extension's planting table counts 3 spring plantings of summer squash, and the zucchini per person page uses that count. In zone 5b that means sowing May 1, again May 15 to May 22, and a third time May 29 to Jun 12; each sowing still has more than 50 days before the Oct 10 frost. The succession planting planner builds those dates for you.

Seeds per mound

Sow 4 to 6 seeds per mound, then thin to two plants once they are up. If you would rather set out transplants, the crop record spaces them 2 feet apart.

Too early does not help

Zucchini is frost tender, and Oregon State's table gives 60°F as the lowest soil temperature for germination. Sowing before the frost date gains little: the seed waits for warm soil, and seedlings that do come up are exposed to a late frost.

Check how many plants fit your bed with the zucchini spacing calculator, and put zucchini on one calendar with the rest of your garden in the seed starting calculator.