Growing Seedless Watermelons

By Charlie Nardozzi

Watermelons are one of the sweetest, juiciest, and most refreshing foods you can grow. They are the quintessential summer snack food. They're not only great tasting, they're good for you as well. Watermelons are loaded with vitamins A, B6, and C and new research has found that they also contain lycopene, a cancer-fighting compound.

While kids may love spitting watermelon seeds as they eat this delicious fruit, you can now find a number of seedless varieties to grow at home. Although they're a little more finicky to grow than seeded varieties, seedless watermelons are much easier to eat and to use in soups and fruit salads.

Seedless Watermelons

The obvious question is, "How do you get seed for seedless watermelons?" Seedless watermelons are actually genetically different from their seeded relatives, and are created through a combination of conventional hybrid breeding and the application of a plant hormone. The resulting seeds have 3 sets of chromosomes (known as triploid seeds). The seeds are sterile, meaning they will produce plants and fruits but the seeds within the fruits are not viable. The fruits tend to weigh 10 to 20 pounds, and the flesh comes in a range of colors from yellow to dark red.

Here are some of the best varieties to try.

'Sweet Slice' looks similar to the classic 'Crimson Sweet'. It has sweet, red flesh and a tough rind. 'Sweet Slice Plus' is a highly disease-resistant version of 'Sweet Slice'. 'Sunny' is a yellow-gold, sweet fleshed variety with a round, oval shape and tolerance to fusarium wilt. 'Orange Sunshine' has deep orange flesh with a tough, sunburn-resistant rind.

Planting and Growing Watermelons

Seedless watermelons require warm soil for germination. After all danger of frost has passed in your area and your soil temperatures are 70 degrees F at 4 inches deep, sow 3 to 4 seeds in hills spaced 3 to 5 feet apart. Thin to the two strongest seedlings.

In cool summer areas, consider starting seedlings indoors to transplant in the garden 2 weeks after your last frost date. Using 2-inch diameter pots, sow 2 seeds per pot and thin to the strongest seedling after germination. Transplant into the garden 3 to 4 weeks later, while they have no more than 3 true leaves per plant - otherwise they won't adjust well to transplanting and will be stressed and stunted.

Seedless watermelons require cross pollination by seeded varieties in order to produce fruit. Sow at least one seeded variety in the area to insure a crop.

Watermelon Care

Watermelon need a lot of water and nutrients. Before planting amend the soil with a 2- to 3-inch-thick layer of compost or composted manure. In cool summer areas, lay black or dark green plastic mulch on the planting beds 2 weeks before planting to heat up the soil. Sow seeds or set transplants at the proper spacing in holes poked through the plastic.

Since watermelons are 90 percent water, they need a constant supply of moisture. Consider running a soaker hose under the mulch to keep soil evenly moist. When watering by hand, apply enough water to soak into the soil to a depth of 6 inches. Keep the area around the plants free of weeds. Side dress the vines with 1/2 pound of a balanced fertilizer when they start to run, and again when the fruits set.

Squash vine borers and cucumber beetles are the primary insect pests of watermelons. (See the "Question of the Week" below for cucumber beetle control options.) Squash vine borers hatch into small larvae that tunnel into vines, eventually causing plants to wilt and die. Cover young plants with a floating row cover to prevent the adult fly from laying eggs. Remove the cover when watermelons begin to flower so they can be pollinated. Inject Bacillus thuringiensis (Bt) in the vines if borers are present or physically remove the larvae by slitting the stem with a sharp razor and picking out the borers. Cover the stem with soil afterwards to encourage the vine to grow new roots and regain its vitality.

To avoid diseases in your watermelon patch, choose resistant varieties, rotate crops, and clean up crop debris in the fall.

Harvesting Watermelons

Deciding when to harvest watermelons can be a challenge. Here are a few cues. When the "belly" (the side of the fruit laying on the ground) turns from white to a creamy yellow color and the overall color of the watermelon dulls, it's time to pick your melon.

Some gardeners can tell if a melon is ripe by thumping it with their thumb. Unripe melons make a "ringing" sound, while ripe ones make a more "muffled" sound.

Also, check the tendrils closest to the fruit. Tendrils are the curly-cues attached to the vines that wrap around nearby plants or other objects to support the vine. When the tendril closest to the fruit turns brown and dries up, the watermelon is ripe.

Don't be concerned if some of the fruits have a few seeds. This is normal, especially if the vines didn't receive enough water. Also, remember that your pollinator plant will produce seeded fruits, while the triploid varieties will be seedless.


Controlling Cucumber Beetles

Q. There are small, narrow beetles with black and yellow stripes chewing holes in my young cucumber plants. What can I do to protect the vines?

A. Cucumber beetles harm plants by feeding on the leaves and flowers, plus they can transmit diseases among melon and cucumber plants. Handpick them or try using row covers to keep them off the plants. If you pin the fabric tightly to the soil, that should also deter "crawling" insects, such as squash bugs. It's important to check under the cover frequently, though, for other pests. And be sure to remove the row covers when for pollination.You can also grow cucumber varieties, such as 'Diva', that don't require pollination to set fruit.

Another trick is to bury a bright yellow margarine tub in the garden with its lip even with the soil line. Coat the inside with a sticky substance, such as Tanglefoot. The cucumber beetles attracted to the color (which resembles cucumber and melon blossoms) and get caught in the tub. Also, try spraying with a neem-based repellent ("neem" is an extract of the neem tree seed) according to the label directions.

About Charlie Nardozzi
Thumb of 2020-06-04/Trish/0723fdCharlie Nardozzi is an award winning, nationally recognized garden writer, speaker, radio, and television personality. He has worked for more than 30 years bringing expert gardening information to home gardeners through radio, television, talks, tours, on-line, and the printed page. Charlie delights in making gardening information simple, easy, fun and accessible to everyone. He's the author of 6 books, has three radio shows in New England and a TV show. He leads Garden Tours around the world and consults with organizations and companies about gardening programs. See more about him at Gardening With Charlie.

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