This winter has been so long, the other day I overheard two snowmen saying even they were looking forward to the spring thaw. Spring gardening will be exhilarating this year.
Many of us who enjoy gardening have special flowers, fruits or vegetables that intrigue us. Since I was a boy, growing watermelons and muskmelons has fascinated me. Part of the thrill is the sweet, flavorful, vine-ripened melons, but my motivation is also to prove that our Upper Midwest gardening region isn’t the last outpost on the way to the Arctic. We can grow melons whose taste is unbeatable.
I first learned the secrets of successfully growing melons in the 1970s from research being done at North Dakota State University in which the Horticulture Department was developing methods tailored to our growing region. Their method has worked successfully in our garden ever since, yielding high-quality watermelons and muskmelons.
Two key ingredients for raising melons are heat and well-adapted varieties. Although our growing season’s temperatures can vary year to year, there are things we can do to increase heat, which when coupled with plenty of sunshine results in large, sweet melons. Besides warm air temperatures, warm soil is essential, as melon roots won’t grow in cool soil below 65 degrees.
Winter’s deeply frozen soil causes it to remain cool into early summer, as the ground thaws and soil warms slowly. A major part of NDSU’s melon research involved coaxing soil to warm more rapidly, giving melons an earlier start and longer growing season.
A reliable way to warm the soil, the research found, is by using clear plastic film laid over the soil early in the season to create a greenhouse effect as warm sunlight is captured below the clear plastic. The plastic prevents heat loss to cool winds and diminishes nighttime heat loss, allowing soil warmth to build. Black plastic, although its surface is warmed by sunlight, doesn’t transmit the warmth to the soil below as effectively as clear plastic.
Successful growing method
- Till garden soil as soon as it’s workable in spring.
- Cut clear plastic, preferably 3 or 4 mils thick, into sections 4 feet wide and as long as the rows you intend to plant with melons. If not planting in rows, use squares of plastic 4 feet by 4 feet for individual plants.
- About May 1, lay the clear plastic directly on tilled garden soil, covering the edges with soil to weight against wind whipping. As sunlight enters the plastic, it will trap heat in the soil for two to three weeks, warming it in advance of planting.
- On May 1, start seeds of watermelon and muskmelon indoors in 4-inch diameter peat pots filled with seeding mix. Plant three seeds per pot, 1 inch deep, and water well. Bottom heat is essential, such as provided by a propagation heat mat. Lack of heat delays germination. Provide high light immediately in an all-day sunny window or under lights.
- Peat pots allow pot and all to be planted outdoors, with little root disturbance. Melon transplants are slow to recover if roots are damaged, which delays crop growth.
- Although melons can be direct seeded outdoors into the garden, using transplants speeds the crop by two to three weeks. Direct seeded melons often ripen too late.
- Accustom melon plants to outdoor conditions by moving the transplants outdoors on sunny, warm days in early May. The ideal melon transplants are about 20 days old.
- Transplant melons into the garden about May 25. After cutting "X"-shaped slots in the plastic, spacing plants 2 to 4 feet apart, install transplants so the rim of the peat pot is below soil surface. Secure the opening in the plastic with handfuls of soil around each plant. When finished, the plant’s leaves extend above the plastic, with the plastic covering its rootzone. Water well, and add a starter fertilizer for faster plant takeoff.
- Rain and irrigation enter the plastic through each planting hole, and from the sides.
- For extra early protection and warmth, clear jugs, containers, or row covers can be added over plants.
The muskmelon cultivar recommended in NDSU’s 1970s research was Gold Star, available from Harris Seeds. To this day, Gold Star continues to be the most successful, large, sweet muskmelon I’ve ever grown. Another favorite is Dakota Sisters from Prairie Road Organic Seeds, Fullerton, N.D. Other melons on NDSU’s 2019 list of recommended varieties include Aphrodite, Athena, Goddess, Solstice and Superstar.
The watermelon that is my hands-down favorite is Sweet Dakota Rose from Prairie Road Organic Seeds, a truly mouthwatering, sugary-sweet delight of excellent size. I also like Sweet Favorite, and NDSU additionally recommends Early Moonbeam and Sangria.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at firstname.lastname@example.org.