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How seedless watermelons are created

May 7, 2026

I recently learned about a watermelon the size of an egg that was hybridized in North Carolina. The hybridizer is Delaney Raptis, a teenager who created this botanical oddity in her suburban backyard. Although the procedure she used is proprietary, the experience of other watermelon hybridizers provides insight into the process typically involved in creating watermelon varieties — from seedless to egg-shaped — that would never have been thought possible at one time.

This story begins 3,500 years ago in ancient Egypt, where an extract from the corms and seeds of the Mediterranean or autumn crocus (Colchicum autumnale) was used for treating rheumatism and swollen joints. This medicinal compound was eventually named colchicine since it grew in abundance in a region of the Greek Empire near the Black Sea known as Colchis. Colchicine was commonly used in Europe for centuries, and in the 18th century was brought from that continent to America by Benjamin Franklin, a notorious sufferer from gout. Gout is an extremely painful inflammatory form of arthritis that causes uric acid crystals to form around joints. Franklin even penned a humorous essay on the subject titled “Franklin and the Gout.”

Colchicine is a highly toxic substance, and treatment with it was curtailed for many years due to its hazardous potential. However, it was later refined and proven to remedy gout by reducing white blood cell division and proliferation that brings on this condition. It was known, however, that substances and processes that arrest cell division in animals lead to a doubling of chromosome number in plants. Moreover, this chromosome doubling in the plant world may occur naturally, with the most famous example being the seedless banana. Seedless bananas sprang up in the wild thousands of years ago when their chromosome number doubled. In any event, colchicine has been utilized in creating bigger petunias, lilies, marigolds, larger and more vigorous strawberries and blueberries, and spearmint and chamomile with a higher than usual concentration of essential oils.

The idea of creating a seedless watermelon came from Japanese scientists who, in the late 1930’s, applied colchicine to young seedlings at their shoot apex when the first true seedling leaves began to form. These seedlings grew into plants with fruit whose seeds contained double the usual number of chromosomes. The normal number of chromosomes in animals and plants is diploid, meaning that they appear in sets of two. However, doubling under the influence of colchicine leads to four sets or a tetraploid number of chromosomes. Here, the phenomenon of a mule was an instructive guide in predicting what would happen when a watermelon with tetraploid chromosomes was crossed with an ordinary diploid variety. A horse has 64 chromosomes, and a donkey has 62. When these animals mate, a mule results. A mule has 63 chromosomes and is sterile, keeping in mind that a mule is born when a male donkey mates with a female horse. (When a female donkey mates with a male horse, the offspring is a hinny, also sterile but much weaker than a mule.)

According to this logic, a tetraploid crossed with a diploid watermelon would yield a triploid plant that would be sterile, and this is how seedless watermelons came to be. An ordinary diploid watermelon has 22 chromosomes, a tetraploid has 44 chromosomes, and combining them results in a sterile tripled variety with 33 chromosomes. When tetraploid and diploid plants are crossed, pollen from the diploids is brushed onto the stigmas of the tetraploids. The resulting plants produce fruit whose triploid seeds are then planted to yield seedless watermelons. Triploid watermelon seeds are available through Internet vendors, but they are expensive and require special treatment for successful germination. It’s useful to be reminded that all melons, in the manner of other cucurbits, namely squash, pumpkins, and cucumbers, are monoecious, meaning they have separate male and female flowers on the same plant, which makes accessing their pollen easier than in the case of the vast majority of flowers that are hermaphroditic.

Incidentally, a seedless watermelon has a longer shelf life than a watermelon with seeds, the former lasting for up to a month following harvest. There are several reasons for this. Seeds produce ethylene that hastens maturation and deterioration of the surrounding tissue. The depressions in watermelon around seeds are also more liable to decay than the solid flesh of seedless types. Finally, seedless types are bred specifically for flesh firmness. In closing, it should be mentioned that just as colchicine treatment results in seedless watermelons, mini-melons may also be a consequence of applying colchicine to watermelon seedlings, followed by a breeding process similar to that described above.

We live in an area of the U.S. that would appear to be more favorable for growing melons than any other. Melons are native to regions of Asia and Africa with a long, hot, and dry growing season similar to Southern California’s. Some melon varieties can even be dry farmed, meaning that their water needs are satisfied by winter rain alone. That is, given our average winter rainfall of 14 inches, if you were to plant seeds of most muskmelon and watermelon varieties in properly prepared and mulched soil in late winter or early spring, you could harvest a crop in the summer without having had to water your plants even once. The difference between dry-farmed and irrigated melons, or any fruit for that matter, is that dry-farmed crops are sweeter, although their yield will be less than irrigated ones. Dry farming of many crops, including melons, was commonplace in Southern California during the early decades of the last century.

You can plant melons any time from now until the end of June. The longer you wait to plant, the faster they will grow since warm soil is much to their liking. For a Halloween pumpkin, however, plant pumpkin seeds from now until the end of June.

Do you have a melon story to tell? If so, send it along via joshua@perfectplants.com. Your questions, comments, and horticultural insights, as well as gardening conundrums and successes, are always welcome in my inbox.

California native of the week: If you’re thinking of planting a slope, a collection of buckwheats is worth serious consideration since there are so many types and, between the various species, you have flowers to look at — in white, pink, red, and yellow — throughout the year. Santa Cruz Island buckwheat (Eriogonum arborescens) has white flowers that turn pink and then burnt orange as they age. Saffron buckwheat (Eriogonum crocatum) has yellow flowers and silver-gray foliage, red buckwheat (Eriogonum grande var. rubescens) has red flowers, and coast buckwheat (Eriogonum latifolium) has pink flowers. Buckwheats are famous for attracting butterflies of every description, and their flowers are wonderful candidates for everlasting arrangements. They are evergreen and will self-sow when soil conditions are favorable.

Orange County Register

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How seedless watermelons are created

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