Seedless Watermelon Breeding

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If you were born before the 1990s, you remember a time before seedless watermelons. Today, the seedless watermelon is immensely popular. I think half the fun of eating watermelons is spitting out the seeds, but then I’m no lady. Regardless, the burning question is, “Where do seedless watermelons come from if they have no seeds?” And, of course, the related query: “How to grow seedless watermelons without seeds?”

Where do seedless watermelons come from?

First of all, seedless watermelons are not completely seedless. There are small, almost transparent seeds found in the melon; they are bland and edible. Occasionally, you will find a “true” seed in a seedless variety. Seedless varieties are hybrids and result from a fairly complex process.

Hybrids, if you remember, don’t reproduce from seed. You may end up with a plant mutt with a mix of traits. In the case of seedless watermelon, the seeds are effectively sterile. The best analogy is that of a mule. Mules are a cross between a horse and a donkey, but mules are sterile, so you can’t herd mules together to get more mules. This is exactly the case with seedless watermelons. You have to raise two mother plants to produce the hybrid.

All interesting info on seedless watermelons, but still doesn’t answer the question of how to grow seedless watermelons without seeds. So, let’s get to that.

Information about seedless watermelon

Seedless melons are referred to as triploid melons while watermelons with ordinary seeds are called diploid melons, which means that a typical watermelon has 22 chromosomes (diploid) while a seedless watermelon has 33 chromosomes (triploid).

To produce a seedless watermelon, a chemical process is used to double the number of chromosomes. Thus, 22 chromosomes are doubled to 44, called tetraploids. Then, pollen of a diploid is placed on the female flower of the plant with 44 chromosomes. The resulting seed has 33 chromosomes, a triploid or seedless watermelon. Seedless watermelon is sterile. The plant will bear fruit with translucent, non-viable seeds or “eggs”.

Seedless Watermelon Growing

Growing seedless watermelon is very similar to growing seeded varieties with a few differences.

First off, seedless watermelon seeds have much harder germination times than their counterparts. Direct sowing of seedless melons should occur when the soil is at a minimum of 70 degrees F. (21 C.). Ideally, seedless watermelon seeds should be planted in a greenhouse or similar with temperatures between 75-80 degrees F. (23-26 C.). Direct sowing in commercial enterprises is very difficult. Overseeding and then thinning out is an expensive fix, as seeds range from 20-30 cents per seed. This explains why seedless watermelon is more expensive than regular watermelons.

Secondly, a pollinator (a diploid) must be planted in the field with the seedless or triploid melons. One row of pollinators should be alternated for every two rows of the seedless variety. In commercial fields, between 66-75 percent of plants are triploids; the rest are pollinating (diploid) plants.

To grow your own seedless watermelons, start with purchased transplants or start the seeds in a warm environment (75-80 degrees F. or 23-26 degrees C.) in sterile soil mix. When the runners are 6-8 inches (15-20 cm) long, the plant can be moved to the garden if soil temperatures are at least 70 degrees F. or 21 degrees C. Remember, you must grow both seedless and seedless watermelons.

Dig holes in the ground for transplants. Place a seedless watermelon in the first row and transplant the seedless watermelons into the next two holes. Continue to stagger your plantings, with one variety sown every other seedless. Water the transplants and wait, about 85-100 days, for the fruit to ripen.

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