When to Plant Summer Squash and Zucchini in South Carolina: Spring and Fall Dates, Coastal and Piedmont

One South Carolina calendar, one crop: summer squash, with the source’s dates left as printed and NOAA frost dates for Charleston International Airport, Columbia Owens Downtown Airport, and Greenville Downtown Airport.

By Paul Gunder · How we check our sources

Updated November 11, 2026

Figures checked against their sources on November 11, 2026; next check May 8, 2027.

For summer squash, Clemson Cooperative Extension prints 2 regions under the heading “Squash, Summer”; the table below copies each entry as printed. How far apart are the rows? 31 days, from March 15 in Coastal to April 15 in Piedmont. The row carries no seed or transplant marking, so the packet or plant tag settles which one the dates fit.

Summer Squash and Zucchini: the South Carolina table

In Clemson’s spacing table the same crop is listed at 50-60 days to harvest, 36 x 15 inches between rows and plants.

Summer squash planting dates in South Carolina, as printed by Clemson Cooperative Extension (one row per region, none averaged)
Region	Spring planting	Fall planting
Coastal	Mar 15 to Jul 31	Aug 1 to Aug 31
Piedmont	Apr 15 to Jul 31	Jul 15 to Aug 15

Reading the Clemson Cooperative Extension table

The factsheet lists the counties of each gardening region: Greenville, Anderson and York are Piedmont counties, while Charleston, Florence and Richland are Coastal Plain counties. The chart’s own heading says Coastal while the county list says Coastal Plain, and this page uses the chart’s wording in its tables.

Starting summer squash indoors

Indoor sowing is the one part of the job no state table above settles. The University of New Hampshire gives 3 to 4 weeks between sowing and transplanting.

Of the saved sources, one gives weeks for summer squash (UNH) and one gives a handling tip (Minnesota).

In the garden itself, UNH sows summer squash once the soil reaches 70 °F, which a soil thermometer answers better than any calendar.

Indoor start for summer squash: what each saved source says (one row per source, none averaged)
Source	What it says
University of New Hampshire	3 to 4 weeks from seed to transplant; 2 weeks after the last frost is safe to set out
University of Minnesota	Cucumbers and squash transplant poorly, so raise them in fiber or paper pots that break down in the soil

Typical frost dates at South Carolina stations

A 50% frost date is a coin flip, not a promise. In half of the years the last spring freeze comes later than the date shown, and in half of them the first fall freeze comes earlier.

The last column maps a station to a region only where Clemson Cooperative Extension or its county list settles it.

NOAA 1991-2020 normals for South Carolina stations: 50% last spring and first fall 32°F dates
Station	Last spring 32°F	First fall 32°F	Region in South Carolina’s calendar
Charleston International Airport, South Carolina	March 7	November 27	Coastal
Columbia Owens Downtown Airport, South Carolina	March 13	November 19	Coastal
Greenville Downtown Airport, South Carolina	March 16	November 20	Piedmont
Florence Regional Airport, South Carolina	March 19	November 13	Coastal
Rock Hill York County Airport, South Carolina	March 31	November 4	Piedmont

Worked example

For a gardener near Florence Regional Airport, NOAA’s even-odds frost dates are March 19 in spring and November 13 in fall.

Coastal’s window for summer squash runs from March 15 to July 31. The opening falls 4 days before the median last freeze, and the close 134 days after it.

On the fall side, Coastal’s last planting date of August 31 leaves 74 days before the November 13 median first freeze.

Treat the result as a way to see how far the printed dates sit from a real frost record. Your yard may run weeks off the station, so repeat the sum with the station closest to you.

Before you rely on these dates

The factsheet was last revised in February 2021.

Treat the table as a starting range and look at the ten-day forecast before setting out anything tender.

Sources (4)