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Winter Squash Seed Starting Tips

Squash winter butternut green 1

Winter squash are tender, warm-weather crops very similar to summer squashes. But, winter squashes—unlike summer squashes—must fully mature on the vine before harvest.

Summer squashes can be picked and eaten immature; they have a succulent texture. Winter squashes are drier and more fibrous than summer squashes.

Winter squashes include acorn, banana, buttercup, butternut, cushaw delicious, Hubbard, marrow, and pumpkin.

Sow winter squash indoor 4 to 3 weeks before the last expected frost in spring. Sow winter 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 mature 60 to 100 frost-free days after sowing.

Winter squash plants seed start
Squash plants early in the growing season

Winter Squash Sowing and Planting Tips

  • Grow winter squash from seeds or seedlings.
  • Squash seeds are viable for 6 years.
  • Direct sow winter 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.
  • Winter squash seeds will not germinate at a soil temperature below 66°F (18°C).
  • To start plants indoors, sow seed in peat pots 4 to 3 weeks before the last frost in spring. The indoor temperature should be 66°F to 85°F (18-29°C) until germination.
  • Sow seed ½ to 1 inch (1.3-2.5 cm) deep.
  • Seeds germinate in 4 to 10 days at 85°F (29°C) or warmer.
  • Transplant winter 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.
  • Winter squash will benefit from the warm soil created by planting on hills or mounds; raise the soil 12 inches (30 cm) tall and 20 inches (50 cm) wide and grow individual plants on hills. Space hills 4 to 5 feet (1.2-1.5 m) 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.
  • Winter squash prefers a soil pH range of 5.5 to 6.8.
  • Grow winter squash in full sun for best yield.
  • Avoid planting winter squash where cucumbers or melons have grown recently.
  • Common 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, and cucumber mosaic.

More tips at How to Grow Winter Squash.

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

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

Winter Squash Planting Calendar

  • 4-3 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 65°
Squash on mound seed starting
Winter squash will benefit from the warm soil created by planting on hills or mounds;

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

  • Acorn: acorn-shaped, dark green fruit to 2 pounds.
  • Banana: smooth gray-green skin, light orange flesh to 18 inches long.
  • Butternut: tan-yellow skin, orange fleshy pulp; elongated pear-shape with a bulbous compartment of seeds at the blossom end
  • Buttercup: squat acorn shape; blackish-green rind with yellow-orange flesh.
  • Cushaw: green-striped gourd to 15 inches long.
  • Hubbard: bluish, gray, orange, or dark green, smooth and warty skin.
  • Pumpkins are winter squashes.
  • Turban: bright-colored, turban-shaped shells 6 to 7 inches in diameter.

Botanical Names: Cucurbita maxima, Cucurbita moschata, Cucurbita pepo.

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

More tips at Squash and Pumpkin Growing Tips.

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. Harvesttotable.com has more than 10 million visitors each year.

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  1. When germinating indoors, is “legginess” something you need to worry about with squash? Mine look a little long, but I’m hoping that it may not matter given squash generally grow along the ground, or climb… they’re not self-supported. Thanks.

    • All young seedlings can grow leggy, including squash. Legginess is caused by the plant stretching for as much sunlight as possible. If your seedlings are growing in a window, be sure to turn them daily–this reduce legginess. If you are growing your seedlings under a grow light, keep the light just a few inches above the seedlings. Gently brush the seedlings each day with the back of your hand or place a fan nearby to give them a gentle breeze; this will help the stems grow strong and stout.

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