Summer Squash and Zucchini Seed Starting Tips

Zucchini seedling

Summer squash 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 prefer 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: Squash are not a good choice for container growing. They require significant room to spread and grow.

Recommended Planting Calendar:

  • 4 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.

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.