Start indoors or direct sow?

Direct sow summer squash because its roots resent disturbance and seedlings grow quickly outside. You may start it indoors briefly in biodegradable pots if your season is short or you want an earlier planting.

When to start Summer Squash seeds

Direct sow 1 to 2 weeks after the average last spring frost, once soil has reached at least about 65°F. For indoor starts, sow 3 to 4 weeks before transplanting after all frost risk has passed.

How to sow the seeds

Sow seeds 1 inch deep in loose, fertile, well-drained garden soil for direct sowing. Indoors, use one seed per 3 to 4 inch biodegradable pot filled with seed-starting mix and do not overgrow the seedlings.

Germination

Summer squash seeds commonly emerge in 4 to 10 days. Keep soil evenly moist and warm, ideally around 70 to 95°F.

Seedling care

Give indoor starts bright light and water at the soil level whenever the mix is beginning to dry. Thin direct-sown seedlings to the final spacing, and prevent damping off indoors with good airflow, clean pots, and moderate moisture.

Transplanting & hardening off

Direct-sown summer squash does not require transplanting. Harden indoor plants off for about a week and transplant them gently at their original soil depth while young.

Tips

Sow extra seeds, then keep the strongest seedlings after emergence. Avoid planting into cold, wet soil because seeds may rot before they sprout.

General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.