Preferred Growing Temperatures
Watermelon plants are very sensitive to frosty conditions and cold temperatures, so it’s important to set plants out or plant your seeds once optimal outdoor conditions are reached. Otherwise, your plants can fail to thrive or seeds germinate.
Optimal temperatures for germination and planting are:
- The best temperatures for germination are between 70°F to 95°F (21.1°C to 35°C). Germination occurs in a couple of days, when seeds are planted in 95°F (35°C) and can take a week, when planted in 70°F (21.1°C).
- Watermelons thrive when planted and grown with temperatures ranging between 70°F and 85°F (21.1°C and 29.4°C), but still handle temperatures of 90°F (32.2°C).
How to Get a Head Start on Planting
Gardeners living in cooler regions where the growing season is shorter can still get a head start on warming the soil of the garden area where the watermelons will be growing and planting your seeds.
- In late winter or early spring, cover the garden area with black plastic, being sure to secure the ends in place. This not only organically kills any unwanted vegetation, but the black plastic helps the soil retain warmth.
- You can also mulch around the watermelon plants with black, plastic mulch, which helps retain heat in the soil.
- Placing fabric row covers over young plants also retains warmth in the soil. However, once the plants start blooming you have to remove the covers for proper pollination of the flowers. Keeping the row covers in place can impede pollination, which reduces the watermelon crop.
- Start seeds indoors in peat pots two to four weeks before the last frost in your area, and plant out in the garden two weeks after the last frost. Like all melons, watermelons have sensitive roots and you can plant the entire peat pot in the garden without disturbing the root system.
Expert Tip: If you live in an area with a long growing season, you can sow the watermelon seeds directly in the garden once preferred outdoor temperatures are reached. Plant the seeds ½ inch deep in the ground and the same depth in peat pots. Florida is the only state where watermelons are grown and harvested year-round.
Varieties of Watermelons
A determining factor of what variety of watermelon you should grow is how long your area experiences a season of consistently warm weather conditions. Watermelons are warm-season crops and true heat-lovers, not performing well under consistently cool temperatures.
However, even those living in the coolest areas of the country have selections that mature early and are more tolerant to cooler climates. When searching for appropriate varieties, check out the “days to harvest” listed on the seed packet and choose those with the shorted number of days for the melon to achieve ripeness.
Some good choices for short-season growers include:
- ‘Blacktail Mountain’ produces 6- to 12-pound, red-flesh fruit with dark green skin. More tolerant to cold and matures in around 70 days.
- ‘Snack Pack’ produces 3- to 4-pound fruits, with dark green skin and red flesh. Matures in around 75 days.
- ‘Sweet Dakota Rose’ an heirloom produces 10- to 20-pound, bright red-fleshed fruits. Good for shorter seasons as it matures in around 60 days.
- ‘Yellow Doll’ is a hybrid producing 3- to 7-pound, yellow-fleshed melons green striped skin. Semi-compact vines mature in 68 to 80 days.
- ‘Yellow Alice’ is a Korean hybrid producing small, round fruits with yellow-flesh. Matures in 55 to 60 days.
If your climate is a bit warmer, giving you alonger season of warm temperatures, there’s quite a variety of watermelons choices.
- ‘Solitaire’ is a seedless hybrid that stores well and produces red-fleshed, 4- to 6-pounds fruits, with dark green, striped skin. Matures in about 88 days.
- ‘Strawberry’ is a hybrid producing sprawling vines and 15- to 20-pound, strawberry red-fleshed fruit with dark green striped skin. Matures in 85 days and disease-resistant.
- ‘Compadre’ is a disease-resistant hybrid producing 20- to 25-pound, red-fleshed and oval fruits. Matures in 82 to 85 days.
- ‘Sunray’ is a hybrid seedless producing yellow-fleshed, 13-pound fruits with light green striped skin. Matures in around 85 days.
- ‘Lamar Premium’ is seedless, producing 10- to 13-pound, red-fleshed fruits with waxy, black-green skin with blackish stripes. Matures in 83 days.
Those experiencing a climate with months and months of consistently warm temperatures have the largest choices in watermelon varieties. They can grow those designed for a shorter season, and cultivars requiring almost four months of warm weather conditions.
- ‘Desert King’ produces yellow-fleshed, 20- to 30-pound fruits with light green skin. Matures in 85 to 100 days.
- ‘Orange Flesh Tendersweet’ produces orange-fleshed, 30- to 50-pound fruits with dark green skin with mottled stripes. Matures in 90 days.
- ‘Allsweet’ is disease-resistant, producing 20- to 30-pound, red-fleshed fruits with green-striped skin. Matures in 95 to 104 days.
- ‘Carolina Cross’ bears 200-pound, red-fleshed fruit with green-striped skin. Matures in around 100 days.
- ‘Bush Snakeskin’ produces shorter vines and 25- to 45-pound, red-fleshed fruits and is disease-resistant. Matures in 100 to 110 days.
Whenever the season is right for you to plant watermelons, make sure you meet their basic growing requirements. Grow in a site that receives full sun and in fertile soil that drains well. Follow the seed packet’s recommendation on proper spacing and water regularly, and before you know it, you’ll be harvesting your sweet crop of pure deliciousness.