Slicing into a “seedless” watermelon can reveal small, white, or occasionally black structures resembling seeds. This often causes confusion, as the name implies their absence. Understanding why these structures appear clarifies the science behind these popular fruits. Seedless watermelons are not entirely devoid of potential seed development.
How Seedless Watermelons Are Grown
Seedless watermelons result from plant breeding, which manipulates the number of chromosomes within the plant. Most watermelons are diploid, meaning their cells contain two sets of chromosomes. These diploid plants produce viable seeds when pollinated.
To create a seedless variety, breeders first produce a tetraploid watermelon, with four sets of chromosomes, by treating a diploid plant with a chemical like colchicine.
The next step involves crossing a tetraploid female plant with a diploid male plant. This results in a triploid plant, which possesses three sets of chromosomes. This uneven number of chromosome sets makes triploid watermelons sterile, unable to produce mature, viable seeds.
Triploid plants cannot produce viable seeds but still require pollination to develop fruit. Growers plant diploid varieties in the same fields to provide the necessary pollen. Bees transfer pollen from these pollinator plants to the triploid flowers, stimulating fruit formation. This process ensures the fruit develops without maturing hard, fertile seeds.
The Types of Seeds You Might Find
The “seeds” commonly found in seedless watermelons are small, white, and soft. These are not fully developed seeds but immature seed coats or ovules that did not mature due to the watermelon’s triploid nature. They are soft and often unnoticed or easily consumed.
Occasionally, a seedless watermelon might contain a few larger, harder black seeds. These are rare and can occur if the triploid plant is accidentally pollinated by a standard diploid watermelon plant, or infrequently, due to a genetic anomaly. Even when these black seeds appear, they are non-viable, meaning they cannot sprout. Their presence does not indicate a defect, but a slight deviation from the intended seedless outcome.
Eating the Seeds
The small, white structures in seedless watermelons are harmless. These soft structures are safe and edible, often consumed without a second thought. They are not hard or bitter and pose no health risks.
If you find one of the rare, larger black seeds, eating them is also harmless. While harder and less pleasant to chew, they are not toxic. The tale of a watermelon growing in your stomach from swallowed seeds is a myth; human digestive systems are too acidic for any seed to germinate.