No matter how you slice it, there is no summer without watermelon. Royal Sweet or Icebox, seeded or seedless, I’m not too finicky about watermelon. According to USDA estimates, each American consumes about 15 lbs. of watermelon a year. By late July I’m way ahead of that mark.
While the interest in personal watermelons is warming up, the demand for seedless watermelons is red hot. Although several years have passed since seedless watermelons were first developed in 1939 at Kyoto University, Japan, they comprise about 70 percent of the watermelons grown in South Carolina.
Just the other day while eating a seedless watermelon with my kids, I lamented about their absence of seeds. Besides missing their crunchiness, I couldn’t showcase my prowess as a long distance watermelon seed spitter.
My kids, on the other hand, wondered where the seeds of seedless watermelons came from. I told them that the parents are two seeded varieties. The male is a diploid variety, that is, a watermelon with the ordinary number of 22 chromosomes. The female parent, however, is a tetraploid variety: one that has been chemically treated to double the chromosome number to 44. (I believe it was at this point in my lecture when they tuned me out.) The resulting hybrid seed is a triploid with a chromosome number of 33. Although these triploid seeds will sprout, the resulting watermelon plant is sterile. The vine flowers and makes fruit, but the fruit are seedless.
Growing seedless watermelons is more challenging than raising ordinary watermelons. Seed of the latter will germinate at 75 degrees. Seedless watermelon seeds, by contrast, need at least 80 degrees and preferably 85 degrees to sprout. The thick seed coat sometimes sticks to the cotyledons on the emerged seedlings requiring them to be carefully removed by hand, although sowing the seed so that the pointed end is down reduces this seed coat-sticking problem. Seedless watermelon flowers must be pollinated to set fruit, but because the plants produce no pollen of their own, a seeded watermelon variety must be grown nearby. These seeded watermelons will set fruit of their own, but these are usually selected to have a different shape or rind color to make
it easy to distinguish the seeded and non-seeded fruits.
While many of you search for seedless watermelons–not me. I¹m look for Charleston Gray watermelons that are too big for the refrigerator, but small enough to lie on a bed of ice in my daughter’s red Radio Flyer wagon. I hope your summer is as sumptuous as mine.