Aah "summer time and the living is easy." It's time for swimming, picnics, and fresh food from the garden. Watermelon is the quintessential fruit of summer. It is as important to 4th of July celebrations as pumpkin pie is to Thanksgiving dinner.

We consider watermelon a fruit, but it is a vegetable. It is a cousin to cucumbers, pumpkins and squash. Although grown primarily for its fruit, all parts of the plant are edible. In fact, the first cookbook published in the United States in 1796 included a recipe for watermelon rind pickles.

Historians believe watermelons originated in the middle region of the Kalahari Desert in Africa. Since they are 92 percent water and easy to transport, watermelons soon became an important source of water for thirsty traders, who began to sell the seeds in cities along early Mediterranean trade routes. Hieroglyphics painted on ancient walls in Egypt indicate watermelons were probably first formally cultivated there some 5,000 years ago. The fruit was so prized it was placed in the tombs of royal Egyptians as food for the afterlife. The cultivation of watermelons continued to spread throughout Africa and, by the 1600's, made its way to England, Spain and China. Watermelons were brought to North America by European colonists and African slaves.

Today more than 100 varieties of watermelon are grown in 96 countries. The United States ranks fourth in worldwide watermelon production. China is currently the world's leading producer. Most watermelons have red flesh, but there are pink, orange, yellow and white fleshed varieties too. Some watermelons also have yellow rinds. The uniquely colored watermelons taste just like the traditional red fleshed ones, but they lend themselves to colorful and unusual serving presentations for this longtime favorite fruit.

Watermelons have been divided into four general categories: picnic, icebox, seedless and yellow flesh. Small, round watermelons are classified as icebox watermelons. This category represents watermelons ranging in size from five to fifteen pounds, which allows them to fit more easily into a refrigerator. The picnic category is for larger watermelons, those weighing from fifteen to fifty plus pounds. The picnics typically have an oblong shape. Starting in 1988, California growers began introducing seedless watermelon varieties. These watermelons do have fewer seeds, but they are not truly seedless. They have soft white seeds that are edible. Occasionally, a few hardened dark ones will be present too. A more recent trend is the personal or mini-watermelon, which weighs from one to seven pounds.

One of the most interesting heirloom watermelons is 'Moon and Stars', thought to have been introduced in 1926. It is a very unusual variety with a dark green rind that is speckled with pinhole to silver-dollar sized bright yellow spots, giving the impression of the night sky. The small specks resemble stars and the larger ones moons. The leaves of the vine are also speckled with yellow. 'Moon and Stars' is one of the sweetest tasting heirloom watermelons available.

The venerable watermelon has undergone more drastic changes than just its color and seed content. One of the strangest developments occurred in Japan when farmers there announced they had perfected a square watermelon by forcing their watermelons to grow in square, tempered glass cases. This surprising innovation was developed to help solve refrigerator space issues. The square melons are designed to easily fit in a refrigerator and can be conveniently stacked at the grocery. The only drawback is the cost, which was $82 when they premiered in 2001.

Producing a good watermelon is difficult in northern climates. The sweetest watermelons grow during long, hot summers, making them better crops for southern regions. Gardeners in northern areas should choose early harvest varieties and use transplants. Mulching with black plastic film helps promote early production by warming the soil. Floating row covers will moderate temperatures around young plants and provide some frost protection in unseasonably cold weather. Some early varieties (70 to 75 days to harvest) which the University of Illinois recommends are Golden Crown, Sugar Baby, Yellow Baby and Yellow Doll.

Proper watermelon harvesting is critical because they do not continue to ripen after they have been removed from the vine. When purchasing watermelons, look for ones that are very heavy and that have a hard rind. The rind color should be appropriate for the variety and have a waxy appearance. Thumping a watermelon is not a reliable method for testing for ripeness. Some watermelons do not produce a dull thud when ripe. Instead, the dull thud may signal an over ripe, mushy watermelon. The most important indicator of ripeness is the underside of the watermelon which sets on the ground. It should be yellow or cream colored. If it is white or pale green, the watermelon is not ready to harvest.

For trivia buffs, the world's largest watermelon to date weighed 268.8 pounds and was grown in 2005 by Lloyd Bright in Hope, Arkansas. And kids-or those young at heart-the world record for watermelon seed spitting is 68 feet, nine and 1/8 inches earned by Lee Wheells from Luling, Texas.

There's nothing like a cold slice of watermelon on a hot day. Mark Twain said, "When one has tasted watermelons, one knows what angels eat." Plus it is a dessert we can enjoy without guilt. It has no cholesterol, virtually no fat and is high in lycopene. Eat up!