How to grow watermelons in northern climates

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watermelon

Watermelon is one of our favorite summer treats; however, my daughter and I have never had much success growing it here in Ohio. But this year is going to be different. We’ve done our homework.

Although watermelons can be grown in all parts of the United States, they seem to prefer the longer growing season and warmer temperatures in the South. To successfully grow watermelons in northern climates, you need to choose the right variety and optimize growing conditions. Use the following tips to get started on your own patch of watermelons.

Choosing a variety

Gardeners in northern areas should choose earlier varieties and use transplants to compensate for a shorter growing season.

Seedless vs traditional. Seedless varieties afford some advantages to traditional varieties of watermelon. For one, they don’t have seeds, which is obviously beneficial because you don’t have to waste time picking them out. Secondly, they are generally sweeter than traditional varieties because they don’t put energy into seed production.

From a consumer standpoint, seedless varieties clearly have advantages. However, from a gardener’s perspective, they are more expensive and difficult to produce. Because seed production is so labor intensive for seedless varieties, their seeds are expensive. Because germination of these seeds is less vigorous than traditional varieties, they have to be started in transplant containers and germination conditions have to be closely controlled. Then, once they are planted outside they need to be complemented with some traditional varieties to ensure pollination occurs.

It’s really up to the individual whether or not the benefits warrant the additional work.

Recommended varieties

Penn State Extension and University of Illinois Extension recommend the following varieties:

Early varieties (70-75 days)

  • Golden Crown
  • Lantha
  • Sugar Baby
  • Yellow Baby
  • Yellow Doll

Main season varieties (80 to 85 days)

  • Carson
  • Charleston Gray
  • Crimson Sweet
  • Madera
  • Parker
  • Royal Sweet
  • Sangria
  • Sunny’s Pride
  • Sweet Favorite

Seedless varieties (80 to 85 days)

  • Cotton Candy
  • Crimson Trio
  • Crisp ’NSweet
  • Gypsy
  • Honey Heart
  • Jack of Hearts
  • Millennium
  • Millionaire
  • Nova
  • Queen of Hearts
  • Revolution
  • Super Crisp
  • Tiffany
  • Tri-X 313

Personal size (80 to 85 days)

  • Leopard
  • Vanessa

Starting seedlings

In northern climates, it’s best to start watermelons indoors to jump-start the growing season. Ideally, you want to start your seedlings three weeks before you’ll be ready to transplant them outside.

The key to success for sprouting watermelons is warm soil with limited watering.

  1. Water the planting media thoroughly the day before planting.
  2. Make sure the soil temperature in the transplant containers is between 75-90 F. This temperature should be maintained from seeding through early seedling growth.
  3. Plant your seeds about 1 inch deep.
  4. Do not water until plants emerge.
  5. Do not transplant until soil temperature reaches 60 F at least 3 inches below the surface of the soil.

When to plant watermelons

As mentioned above the soil should be at least 60 F, but it needs to be consistent. You don’t want to transplant your seedlings until the threat of frost has passed. Late May is usually ideal for transplanting watermelons.

Planting watermelons

Optimal growing conditions. Watermelons prefer to be grown in a sandy loam soil; however, not all parts of the country have ideal soil conditions. In Ohio, a lot of areas are clay heavy. This is why raised beds or raised planting rows are frequently used for growing watermelons. Penn State Extension recommends, raises beds covered with black, green, IRT (infrared-transmitting), or silver plastic mulch, with drip tape buried 2-3 inches below the soil surface. The plastic mulch helps keep soil temperatures high, while drip irrigation ensures optimum plant growth and yields and allows growers to apply fertilizer during the growing season.

Spacing and depth. Watermelon vines require a lot of space to spread out. The University of Illinois Extension recommends leaving 7-10 feet between rows and at least 2-3 feet between transplants within rows.

Care. Regular weeding will be required, but watering is rarely necessary unless the weather is dry for a prolonged period.

Harvesting

Use these indicators to determine when your watermelon is ready:

  1. Light green, curly tendrils on the stem near the point of attachment of the melon usually turn brown and dry.
  2. The surface color of the fruit turns dull.
  3. The skin becomes resistant to penetration by the thumbnail and is rough to the touch.
  4. The bottom of the melon (where it lies on the soil) turns from light green to a yellowish color.

Storage

Once watermelons have been harvested, cooling them to 45-50 F will remove field heat and improve shelf life and taste. Watermelons will retain good quality for approximately 21-28 days if stored at 85-90 percent humidity and 47-55 F.

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Sara is Farm and Dairy’s online content producer. Raised in Portage County, she earned a magazine journalism degree from Kent State University. She enjoys spending time with her daughter, traveling, writing, reading and outdoor recreation.

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