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Summer Squash and Zucchini Seed Starting Tips

Zucchini seedling
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.

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9 Comments

  1. 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.

  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. 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.

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