When to plant / Zucchini

When to plant zucchini

Plant zucchini from the last spring frost date to 1 week after it. Zucchini are a tender crop in Colorado State University Extension's planting guide, and that is the guide's rule for the class. Across the 39 U.S. cities on this site the window opens between Feb 9 (Sacramento, CA) and May 13 (Concord, NH), because each city's own NOAA last-frost date is different.

The planting rule for zucchini, in plain words

Colorado State's Vegetable Planting Guide sorts vegetables into four frost classes and gives each class one timing rule relative to the average last spring frost. Zucchini sit in the tender class, whose rule reads: From seed: around the date of the average last spring frost On this site that becomes 0 to 1 weeks from the station's 50% probability last 32°F date, the same arithmetic every city calendar uses.

Colorado State lists summer squash as seed or transplant with a 2–3 week transplant age and 50 typical days to harvest, which is why an indoor column appears below even though Minnesota, quoted next, prefers seed in the ground.

Zucchini is a summer squash. The University of Minnesota lists it that way (Summer squash (Cucurbita pepo), including zucchini, crookneck, straightneck, patty pan and other similar types.), so the class rule used here is Colorado State's summer squash row. Minnesota's own advice is blunter on soil than on frost: sow seeds after the last frost date, once soil temperatures are at least 70° F. and Direct seeding is preferred for starting squash. It also suggests a second sowing: seed only part of your squash garden at first, and then finish the planting three weeks later.

Soil temperature for zucchini

Minimum soil temperature for zucchini in the cited sources: 60°F at 2 inches (Colorado State: 60°F minimum germination for summer squash; Minnesota: at least 70°F at the two-inch depth). A frost date cannot see the soil, so take a morning reading before trusting the window; the soil temperature guide covers every crop.

Zucchini: planting dates for 39 U.S. cities

The rule above applied to each station's own NOAA normals, earliest first. City links open that station's full calendar.

Fall column: 50 days to harvest counted back from the first fall 32°F date (Purdue HO-66-W method, methodology).

3 frost-free stations are left out. Not in the table? The planner takes any pair of frost dates.

Three cities, one rule

• Sacramento, California — last spring frost Feb 9, so direct sow (or transplant) Feb 9 – Feb 16; start seeds indoors Jan 19 – Feb 2; second sowing Mar 2. 297 frost-free days in all.
• Kansas City, Missouri — last spring frost Apr 12, so direct sow (or transplant) Apr 12 – Apr 19; start seeds indoors Mar 22 – Apr 5; second sowing May 3. 194 frost-free days in all.
• Concord, New Hampshire — last spring frost May 13, so direct sow (or transplant) May 13 – May 20; start seeds indoors Apr 22 – May 6; second sowing Jun 3. 140 frost-free days in all.

Related planting dates

• When to plant cucumbers — from the last spring frost date to 1 week after it
• When to plant pumpkins — after the last spring frost, once the soil has warmed
• When to plant tomatoes — 2 to 4 weeks after the last spring frost
• All crops · calendars by city · cool-season vs warm-season crops

Sources for this page

Every date in the table is arithmetic on the station's NOAA normal and the offset stated by the source; the quoted sentences are the only figures on this page that are not computed. Normals are 30-year averages and describe the station, not your yard. Rules checked 2026-10-23; see the methodology page.