When to Plant Zucchini and Summer Squash: Soil Temperature and Dates by Frost

Zucchini grows so fast that there is no prize for planting it early. A seed sown into warm soil a week late usually catches up with, and passes, one that sat in cold ground. What matters more is planting into warm soil, giving the plants room, and planning a second sowing before the first plants tire out.

Step 1: wait for warm soil

University of Minnesota Extension says to plant squash seeds after the danger of frost has passed and the soil is at least 70°F at a 2-inch depth, which is late May in most of Minnesota and early June farther north. Texas A&M AgriLife Extension puts it simply: squash does not grow well in cool weather, so plant in spring after all danger of frost has passed. Texas A&M also notes that warm-season crops grow poorly or not at all when the soil is below 65°F. A soil thermometer pushed in at seed depth in mid-morning tells you more than the calendar does.

Step 2: dates by last frost

Our planting calendar gives zucchini and summer squash a direct-sow window from your average last frost to about a week after. The second-sowing column follows UMN's suggestion to plant part of your seed first and the rest about 3 weeks later.

Regional examples from extension sources: in central Maryland (last frost around April 15), UMD lists summer squash from May to mid-June. University of Florida IFAS lists squash seeds for March to April (and August to September) in North Florida, January to April (and August to September) in Central Florida, and September through March in South Florida.

Step 3: seeds, not transplants

UMN says direct seeding is the preferred way to grow summer squash, and that transplants often fail or are set back when their roots are disturbed. If you do start seeds indoors to beat a short season, sow only a few weeks ahead in pots that can go into the ground whole, and plant them out before they outgrow the pot.

Step 4: plant a second round

Squash plants produce heavily for a few weeks and then slow down, and pests and diseases tend to build up as the season goes on. UMD notes that bush beans, cucumbers and squash slow down after 3 to 4 weeks of harvest. A second sowing about 3 weeks after the first (UMN) gives you fresh, vigorous plants just as the first ones fade. Our succession planting guide has intervals for other crops.

Step 5: fall squash in hot-summer areas

Where summers are long, a late-summer planting gives a fall harvest, and Texas A&M says to plant early enough for the squash to mature before the first killing frost. Average fall planting dates for summer squash by Texas gardening region:

Elsewhere, count back from your first fall frost using the days to maturity on your seed packet and add a couple of weeks, since growth slows as days shorten.

Harvest timing

Texas A&M says to harvest summer squash while the fruit and seeds are small, and to keep picking so the plants keep producing. Check plants every day or two once they start; zucchini can go from just right to oversized very quickly. Texas A&M notes summer squash keeps in the refrigerator for about a week.

Where squash goes in the garden

Squash is a cucurbit, like cucumbers, melons and pumpkins, and shares their pests. See what to plant with zucchini for listed companions and layouts, the Three Sisters garden for growing squash with corn and beans, and when to plant cucumbers for a crop on the same warm-soil schedule.

Frequently asked questions

When should I plant zucchini outside?

After your last spring frost, once the soil is about 70°F (UMN measures at 2 inches deep). That is usually from the frost date to about a week after.

Can I plant zucchini before the last frost?

Not unprotected. Squash is killed by frost and grows poorly in cold soil. Black plastic mulch and row covers can let you plant a little earlier.

Should I start zucchini seeds indoors?

Usually not. UMN says direct seeding is preferred and transplants often fail or are set back. If you start indoors, sow only a few weeks ahead in pots that go into the ground whole.

How often should I plant zucchini?

UMN suggests planting part of your seed first and the rest about 3 weeks later, so new plants are producing when the first ones slow down.

Is it too late to plant zucchini in July?

Often not, if you have enough days before your first fall frost. In Texas, A&M lists fall summer-squash planting dates from August 1 in the coldest region to October 10 in the warmest.

Does this apply to yellow squash too?

Yes. Yellow crookneck, straightneck, pattypan and zucchini are all summer squash and are planted the same way.