When to Plant Squash Seeds?

Squash requires a well-drained soil with good aeration. Select a site that provides full sun, and wait three years between planting squash and members of the Cucurbitaceae family in the same site, as all members of the family -- including cucumbers, watermelons, squash and pumpkins -- are susceptible to the same diseases. The University of Missouri Extension suggests rotating these crops with tomatoes, potatoes or peppers.

You may guess that summer squash is a warm season crop from its name, but winter squash are also tender plants. Summer squash may be planted in spring for summer harvest and in mid- to late summer for fall harvest. Winter squash may be planted either late in the spring or in the height of summer. Timing is important for winter squash if you hope to produce a particular fruit for a local fair or a holiday. For example, if you hope to have pumpkins ready near Halloween, the Clemson Cooperative Extension suggests planting most varieties by early July to ensure they ripen in time.

Avoid planting squash outdoors until all risk of frost has passed. While last frost dates offer you a general guideline for planting, conditions vary year to year and vary due to local features. For these reasons, the recommended method for determining when it is safe to plant squash involves measuring the soil temperature. Squash germinates best after the soil temperature is more than 60 degrees F at a depth of 4 inches over several days.

Outdoors, summer squash seeds should be set 1/2 inch deep. If you plant in rows, place the seeds 4 to 6 inches apart. If you plant in hills, place a ring of three or four seeds on the top of each hill. The hills should be 3 to 4 feet apart; leave 4 to 6 feet between the rows. Plant winter squash seeds 1 inch deep. If you start several seeds in a hill, thin winter squash to one plant per hill after the plants emerge. Use the same spacing for your hills and rows as with summer squash.

Save space by planting bush or short-vined varieties. These require hills spaced 2 to 3 feet apart and rows 3 to 5 feet apart. Large-vined squash require additional space, with hills 3 to 5 feet apart and rows 6 to 8 feet apart. Because the taproots of the plants are prone to damage during transplant, the University of Minnesota Extension recommends against starting plants indoors.

Start spring plantings of squash beneath black plastic mulch. The Clemson Cooperative Extension suggests growing fall plantings of squash on white polyethylene mulch. Create a hole in the mulch to plant each seed and to allow the plants an opening to emerge through the barrier. Mulch shades out most weeds, may help prevent some diseases and helps warm the soil if you plant early in the season.