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Summer Squash and Zucchini Seed Starting Tips

Seedling Zucchini
Zucchini seedling
Zucchini seedling

Summer squashes are tender, warm-weather crops. Summer squashes include crookneck, pattypan, straightneck, scallop, vegetable marrow, and zucchini.

Sow summer squash indoors 4 to 3 weeks before the last expected frost in spring. Sow summer squash outdoors when the soil temperature has warmed to 70°F (21°C). Protect squash in the garden from cool temperatures with row covers.

Summer squash matures 50 to 60 frost-free days after sowing and will bear fruit for weeks as long as the weather remains warm.

Sowing and Planting Tips:

  • Grow summer squash from seeds or seedlings.
  • Seed is viable for 6 years.
  • Direct sow summer squash in the garden in spring after all danger of frost has passed and the soil has warmed to 70°F (21°C). In warm-winter regions, sow squash in midwinter for harvest in early summer.
  • Summer squash seeds will not germinate at a soil temperature below 60°F (15°C).
  • To get an early start, sow seed indoors 4 to 3 weeks before planting out. The indoor temperature should be 80 to 90°F (27-32°C) until germination. Grow seedlings at 75°F (24°C).
  • Start seed indoors in peat pots filled with seed starting mix.
  • Sow seed ½ to 1 inch (13mm-2.5 cm) deep.
  • Seeds germinate in 7 to 10 days at 85°F (29°C) or warmer.
  • Transplant summer squash into the garden after the soil has warmed to at least 70°F (21°C).
  • Space plants in the garden 12 to 18 inches (30-45 cm) apart in all directions.
  • Thin successful plants to 36 inches (90 cm) apart.
  • Water to keep the soil from drying.
  • Fertilize with fish emulsion or a soluble complete fertilizer at half strength.
  • Add aged compost to planting beds in advance of transplanting.
  • Summer squash prefers a soil pH of 5.5 to 6.8.
  • Grow summer squash in full sun for best yield.
  • Avoid planting summer squash where cucumbers or melons have grown recently.
  • Common summer squash pest enemies include aphids, cucumber beetles, flea beetles, squash bugs, squash vine borers, slugs, and snails.
  • Common diseases include bacterial wilt, fusarium wilt, downy mildew, powdery mildew, cucumber mosaic.

Interplanting: Plant summer squash with bush beans, corn, dill, eggplant, lettuce, cucumbers, squash, and tomatoes.

Container Growing: Squashes are not a good choice for container growing. They require significant room to spread and grow.

Summer Squashes Planting Calendar

  • 4-2 weeks before the last frost in spring: start seed indoors for transplanting into the garden later.
  • 2-3 weeks after the last frost in spring: transplant seedlings to the garden.
  • 3 weeks after the last frost in spring: direct sow seed in the garden; minimum soil temperature is 65°F; protect with row covers if nights or days are cool.
Summer squash plants
Summer squash matures 50 to 60 frost-free days after sowing and will bear fruit for weeks as long as the weather remains warm.

Summer Squash Recommended Varieties

There many types and varieties of summer squash; here are a few:

  • Zucchini: glossy, dark green or yellow cylindrical fruits; ‘Gold Rush’, ‘Spacemaster’; ‘Eightball’ is round.
  • Scallop or pattypan: ‘Sunburst’, ‘Starship’, ‘Golden Scallopini Bush’.
  • Round or globe: ‘Eight Ball’.
  • Crookneck and Straightneck

Botanical Name: Cucurbita pepo

Summer squash are a member of the Cucurbitaceae family; other members cucumbers, melons, watermelon, and pumpkins.

More tips: How to Grow Summer Squash.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.


Comments are closed.
  1. I live Alaska where it’s the coldest in the winter and warmest in the summer. I have tried growing zuchini and tomatoes with no success. How can I be successful? Thank you for any ideas.e

    • Plant and grow tomatoes and zucchini in the warmest time of the year. If the soil is not well-drained plant in raised beds. If the nights are cool–less than 60F–protect plants by covering them with row covers or plant in a plastic tunnel. Warm nights are essential for fruiting vegetables to succeed. Feed plants with a dilute solution of fish emulsion every 10 days.

  2. It says not to plant where cucumbers were previously planted then says
    Interplanting: Plant summer squash with bush beans, corn, dill, eggplant, lettuce, cucumbers, squash, and tomatoes.

    Kind of confusing!

    • It is best to not plant squash where cucumbers previously grew; the two use draw the same soil nutrients and are susceptible to the same diseases. Interplanting is not successive planting–or planting in the same location–inter-planted crops will be neighbors at the same time in the garden.

  3. Dear Mr. Albert: I am wondering as a general rule what is the shelf life of vegetable seeds? I have eggplant, pepper, tomato, beet and carrot seeds which I purchased in 2014 – 2017. I used some of them and the remaining seeds are stored in shoe boxes in their little paper envelops. I am debating whether to buy new seeds labeled as ‘packed for 2018’ or will I be able to use the old seeds and still get good germination rate with these old seeds. Any input from you will be greatly appreciated. Thank you

    • Eggplant seeds are viable for about 4 years, peppers 2 years, tomatoes years, beets 4 years, and carrots 3 years when stored in a cool dry place. Most seed growers will label the year of the seed they sell; so check the packet for either the sale year or expiration year. If you want to test the viability of the seed you have place 10 seeds from each variety on a wet paper towel; place the paper towel in a plastic baggie; set the baggie in a warm place and wait for germination; could the seed that germinate and you will know the germination rate.

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