By George Boyhan
University of Georgia

Watermelons are still a summer favorite, and Georgia is still one
of the nation’s top producers. With summer right around the
corner, look for some new watermelons on the market. They’ll cost
more. But they’ll be worth it.

Melons come in many shapes and sizes, and seed companies keep
coming up with new varieties.

One way seed companies have spurred new demand is by developing
seedless varieties. Seedless watermelons aren’t really seedless.
But the seeds don’t develop completely. They remain soft and
edible.

More recently, larger seedless melons in the elongated 20- to
25-pound class have been released. These long melons will often
have a dark rind with a narrow, light green or yellow stripe.
Often called an Allsweet type, these larger seedless melons
should quickly become a favorite with shoppers.

Smaller, too

Small watermelons (less than 10 pounds) have been around for many
years, too. They’ve often been sold in roadside and local
markets. They come with names like Sugar Baby, Minilee and
Mickilee.

These small melons were called icebox types because they could
fit in a refrigerator. Recently, seed companies have been
offering something called personal melons. These new small melons
have the added benefit of being seedless.

The personal melons don’t generally produce as well as larger
melons, so farmers are reluctant to grow them. After all, they’re
paid by weight.

The seed companies have overcome this, though, by contracting
with farmers to grow them. They’re handling marketing and sales
directly as well.

To know how seedless watermelons are grown, you need to
understand basic genetics.

Chromosomes

All higher organisms start out with two complementary pairs of
chromosomes. During reproduction, the number is halved to one, so
it can mate with a complementary chromosome. This is called
sexual reproduction. It’s essentially the same in all higher
organisms.

In watermelons, it’s possible to double the number of chromosomes
from one pair to two pairs, or four chromosomes. During
reproduction, halving the chromosomes leaves two instead of one.
When this is mated with a normal watermelon, the resulting seeds
have three sets of chromosomes.

Growers plant these seeds, and when the plants are pollenized,
the reproductive cells have one and a half chromosomes, which
aren’t capable of mating properly with the one chromosome from
the normal pollen. So the seeds then never develop.

Triploids

These seedless varieties are properly called triploids. Triploid
watermelons have been around for years, usually as small, round
melons in the 10- to 20-pound range.

A watermelon innovation that won’t affect shoppers directly is
how triploids are grown. Triploid melons don’t produce viable
pollen, so up to one-third of a field has to be planted with
normal watermelons to have pollen available for the triploids to
grow.

Seed companies are working on pollenizer plants that are small
enough to be interplanted in a field. This means a grower can
have an entire field planted to triploids and get dramatically
more of these popular melons.

One-third of Georgia farmers’ vegetable acreage is used to grow
watermelons. There are still plenty of the traditional, seeded
melons. But if the new seedless types appeal to you, look for
them as summer arrives.

(George Boyhan is an Extension Service horticulturist with the
University of Georgia College of Agricultural and Environmental
Sciences.)