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When to Plant Cucumber Seeds

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

Tomato and pepper seedlings in trays under an LED grow light

Cucumber 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 23cucumber

Average frost dates: last Apr 23, first Oct 22 (zone 6b).
Season
Spring seed starting schedule
CropSow outdoorsNotes
CucumberTenderApr 23Sow outdoors at last frost. Sprouts in 6 to 10 days, best at 60 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 cucumber seeds

Sow cucumber seed outdoors on your average last frost date, once the soil has warmed to 65 to 70°F. That is the timing in Colorado State University Extension's vegetable planting guide and Utah State University Extension's cucumber guide. Seed will not germinate below 50°F, and in warm soil it sprouts in 6 to 10 days. Oregon State University's germination table puts the best soil range at 60 to 95°F.

Cucumbers are a direct sown crop in these sources, so the planner above gives a Sow outdoors date rather than an indoor start. There is no benefit in sowing before the soil warms: cold, wet seed just sits.

Example dates by zone

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

ZoneLast frostSow outdoorsFirst fall frostDays left for the crop
5bMay 1May 1Oct 10162
7aApr 16Apr 16Oct 25192
9aMar 3Mar 3Nov 25267

Cucumbers need about 55 days from seeding to the first harvest by Colorado State's count, so even zone 4b, with a May 8 sowing and 146 days before the Oct 1 frost, has room for more than one planting. Your own ZIP code can differ from the zone median by a week or more; enter it in the planner for dates from the nearest weather station.

Should you start cucumbers indoors?

The crop records here give no indoor start, and the planner follows them. If you do want a head start, Clemson Extension's seed starting table allows only 3 to 5 weeks from sowing indoors to setting out for cucumber, much shorter than for tomatoes. Keep transplants small and set them out after the frost date, since vine crop roots do not like being disturbed.

Sowing and thinning

  • Depth: 1 inch, per Colorado State.
  • Seeds per hole: 4 to 6, then thin to the strongest plants.
  • Spacing after thinning: 12 to 18 inches in the row, or 9 to 12 inches along a trellis. The cucumber spacing calculator counts plants for your bed or row.

A second sowing

Virginia Cooperative Extension's planting table lists 2 to 3 spring plantings of cucumber. A later sowing replaces vines that slow down in midsummer; check that the days left in your zone still cover the 55 days to harvest. The succession planting planner lays out sowing dates across the season, and the seed starting calculator puts cucumbers on one calendar with the rest of your garden.