Gardeners selecting and planting warm-season crops may include hills of watermelon and muskmelon along with rows of produce. Iowa State University Extension and Outreach horticulture specialists offer planting tips and describe muskmelon and watermelon variety choices for Iowa. Home gardeners with additional questions can contact the experts by calling or emailing the ISU Extension and Outreach horticulture hotline at 515-294-3108 or firstname.lastname@example.org.
Melons are relatively easy to grow. Their basic requirements are full sun and a fertile, well-drained soil. The planting site should receive at least six hours of direct sun each day. Heavy, poorly drained soils can often be improved by incorporating organic matter, such as compost or well-rotted manure, into the soil.
Muskmelon and watermelon are warm-season crops. Plant melons after the danger of frost is past and soil temperatures have warmed to 60 to 70 degrees Fahrenheit. Melons can be planted in mid-May in central Iowa. Gardeners in southern Iowa can plant about one week earlier. Plant one week later in northern areas of the state. The last practical date to sow early maturing muskmelon and watermelon varieties is June 20.
Suggested muskmelon varieties for Iowa include ‘Earlisweet’ (early maturing, 2 to 3 lb. fruit), ‘Eclipse’ (round 6 to 8 lb. fruit), ‘Athena’ (oval 4 to 6 lb. fruit), ‘Aphrodite’ (oval 6 to 9 lb. fruit), ‘Superstar’ (oval 6 to 8 lb. fruit ), ‘Ambrosia’ (round 4 to 5 lb. fruit), ‘Hale’s Best’ (oval 4 to 5 lb. fruit, heirloom), ‘Earlidew’ (honeydew type, pale green flesh) and ‘Passport’ (hybrid melon, green flesh).
Excellent watermelon varieties include ‘Crimson Sweet’ (red-fleshed, seeded, blocky round fruit, 20 to 30 lb.), ‘Royal Sweet’ (red-fleshed, seeded, blocky oval fruit, 20 to 25 lb.), ‘Sangria’ (red-fleshed, seeded, blocky oval fruit, 20 to 26 lb.), ‘Crunchy Red’ (red-fleshed, seedless, round to oval fruit, 15 to 18 lb.), ‘Gypsy’ (red-fleshed, seedless, round fruit, 13 to 17 lb.), ‘Millionaire’ (red-fleshed, seedless, oblong fruit, 13 to 20 lb.), ‘Sweet Beauty’ (red-fleshed, seeded, oblong icebox-size fruit, 5 to 7 lb.), ‘Yellow Baby’ (yellow-fleshed, seeded, round fruit, 9 to 12 lb.), and ‘Amarillo’ (yellow-fleshed, seedless, round fruit, 12 to 14 lb.).
A seeded variety (pollenizer) must be planted with seedless watermelon varieties for proper pollination. Pollinator seeds are often included in seedless watermelon seed packets.
Muskmelon and watermelon are usually planted in hills. Plant four or five seeds per hill at a depth of 1 inch. Later, remove all but two or three healthy, well-spaced plants per hill when seedlings have one or two true leaves.
Hills of muskmelon should be spaced 3 to 5 feet apart with 5 to 7 feet between rows. Watermelon hills and rows should be spaced 6 to 8 feet apart. If garden space is limited, bush-type varieties of muskmelon and watermelon are available.
To obtain an earlier crop, start melon transplants indoors. Sow seeds indoors three to four weeks before the anticipated outdoor planting date. Plantable containers, such as peat pots, work best as both plant and container are transplanted directly into the garden, resulting in little damage to the transplant’s root system. Sow three or four seeds per container, later remove all but two seedlings. Transplant outdoors when plants have one or two true leaves. Harden the plants outdoors for a few days prior to planting to lessen transplant stress. Initially place the transplants in a shady, protected location and then gradually expose the plants to longer periods of direct sun.
Black plastic mulch can also be used to obtain an earlier melon crop. Black plastic promotes spring growth by warming the soil. The plastic mulch also helps to conserve soil moisture and control weeds. Lay the black plastic over moist soil on a calm day. Anchor the edges of the plastic mulch by making furrows 2 or 3 inches deep, placing the edges in the furrows, then covering with soil. To plant, cut holes in the plastic with a sharp knife or bulb planter. The holes should be in the center of the plastic film and just large enough to plant the seeds or transplants.