If you want an abundant crop of orange pumpkins for use at Halloween or for making pies for Thanksgiving, Ohioans must prepare a garden plot and plant after danger of frost passes in spring. Depending on pumpkin cultivar, a warm growing period of 100 to 120 days allows the pumpkin vine to flower and develop harvestable fruits. If possible, time the spring planting so that the pumpkins ripen on the vine in early October.
Pumpkins do not tolerate frost. Across the vast majority of Ohio, the last frost in spring occurs anytime from April 21 to May 10, depending on latitude and elevation. Contact your local cooperative extension office to learn of the last spring frost date in your county, or speak to staff at your local garden center. Wait an additional two to four weeks after your area's last frost date to allow the garden soil to sufficiently warm to at least 65 degrees Fahrenheit. An appropriate pumpkin planting time frame is from mid-May to early June in most parts of Ohio.
Because pumpkins take 100 to 120 days from germination to harvest, you don't want to plant pumpkin seeds or transplants too early in spring. Although you must avoid frost, cool soil temperatures inhibit growth and may lead to root rot. Pumpkins tend to soften and rot on the vine if they ripen too early, such as in late August or September. Aim for pumpkins to pick around October 1. Look at the pumpkin seed packet for the "days to harvest" data. Count backward that number of days from the target October harvest date. This provides you the ideal sowing date in your Ohio locale.
Planting Pumpkin Seeds
Sow pumpkin seeds in hills. A hill is a shallow planting basin about 1 inch deep and 6 to 10 inches wide. Place four or five pumpkin seeds in the hill and cover with 1 inch of soil. Additional hills need to be spaced 6 to 10 feet apart. Hills oriented in long rows need about 15 feet between rows. This allows room for the sprawling vines to grow and still receive ample sunlight.
Growing Giant Pumpkins
Everyone admires a gigantic pumpkin to use as a jack-o' lantern around Halloween. The pumpkin varieties that produce the largest fruits need at least 120 days to germinate, grow and produce ripe pumpkins. According to David A. Mangione of the Ohio State University Extension, it's behooving to start seeds of these long-maturation pumpkins indoors about two weeks before planting them outdoors. He suggests sowing seeds indoors in late April and transplanted them outdoors in May or June when soil is warm and frosts no longer occur.