Sow squash seeds in the garden-or set out seedlings started indoors-only after the soil has warmed to at least 60F usually no sooner than 3 weeks after the last frost in spring. Start squashes indoors as early as 4 weeks before the last average frost date in spring. Sow seed indoors in biodegradable peat or paper pots that can be set directly in the garden so as not to disturb plant roots. Summer squashes grow best in air temperatures ranging from 60 to 75F; established fruit will ripen in temperatures as high as 100F but flowers will drop in high temperatures. Squashes are warm season crops and very sensitive to cold and frost. Summer squashes require 50 to 65 days to reach harvest. Planting and spacing. Sow squash seeds 2 to 3 inches deep. Sow squash in raised hills or inverted hills 4 to 5 seeds set 3 to 4 inches apart: thin to the two strongest seedlings. Space hills 6 to 8 feet apart. In rows plant 2 squash seed 10 inches apart in rows 3 to 5 feet apart; thin successful seedlings in rows to 3 feet apart. Thin seedlings by cutting off weak seedlings at soil level with scissors so as not to disturb fragile roots. Hills or mounds should be 6 to 12 inches tall and 20 inches across.