History and varieties
Watermelon (Citrullus lanatus) is probably the best known melon in the world. It is a member of the Cucurbitaceae family, which also includes cucumbers, summer squash, and other melons such as cantaloupe and honeydew. Like other melons, watermelon is native to central Africa. It was first cultivated by the Ancient Egyptians and quickly spread throughout Africa and to warmer regions in Asia Minor, the Middle East, and even as far north as Russia. During this early period watermelons were used mainly as a source of water rather than a source of food. The Moors helped spread the melon to Western Europe when they invaded Spain in 700 AD. From there, early settlers brought the melon to Massachusetts in America in the early 1600s. The fruit was popular with both settlers and Native Americans and crops quickly spread down the Atlantic coast all the way to Florida. Today, watermelon is mainly grown in the United States in Texas, California, Georgia, and Florida.
Watermelon is the number one melon grown and consumed in the world, followed by cantaloupe and honeydew. The average American consumer eats about 13 pounds of watermelon annually. Besides consuming the flesh, watermelon rinds are often pickled (see Watermelon Pickles for a recipe) and the watermelon juice can be fermented to make an alcoholic drink (see Making alcohol from a watermelon for do it yourself instructions!) In regions of Russia the juice is also boiled down to make a syrup like molasses used for sweetening.
There are hundreds of varieties of watermelon currently grown around the world, but only about fifty or so are available on the market. All these varieties have a similar sweet flavor but they differ greatly in size, the color of the flesh, and whether they are seeded or seedless. The average size of a large watermelon, often called a “picnic melon”, is about forty pounds, but new varieties such as “icebox melons” can weigh as little as five. The color of the flesh is normally pink, but can also be yellow or white. Seedless varieties tend to be more expensive than seeded, but make preparation and eating much more enjoyable. The newest, oddest variety of melon was created in Japan. These melons are square instead of round so they can fit better in small refrigerators (read more about this variety here.)
Watermelon plants and growing watermelons
Watermelon plants are long vines with large green leaves that grow on the ground. These plants prefer hot and humid environments. Each plant produces both male and female flowers that are pale green-yellow. Male flowers outnumber female flowers by as much as ten to one. The female flowers can be identified by a slight bulge at their base. The flowers only open for one day and must be pollinated by honeybees. After pollination the fruit fully develops over the course of about four months. Watermelons can weigh from five to fifty pounds depending on the variety and each vine typically produces two to three melons each. The melons have a thick outer rind that is green with white or yellow streaks. Inside the rind is a sweet and extremely juicy flesh spotted with hundreds of black or white seeds (except for the seedless varieties). The flesh is made up of about 90% water, which means that a forty pound melon contains about 4 gallons of water. Once ripe, the fruit is generally picked by hand to prevent cracking or bruising the rind.
Watermelons and other melons are a fine addition to any summer garden. However, this fruit is more suited to larger gardens because of its long vines. Watermelon plants really need two things to grow well. First, they need to be warm, so make sure you are in a climate with summer temperatures around 70 ° F. Also, plant the seeds well after the danger of frost. Second, since the fruit is made up of mostly water the plants need plenty of water, either by irrigation or lots of rain. One suggestion is to thoroughly water the plants just until they start to grow melons and then cut back the amount of water. This is thought to keep the fruit from being water-logged and less sweet. Plant watermelon seeds in loose, sandy foam soil to a depth of one inch. Most gardeners tend to overplant initially and then thin the plants as they grow. If you don’t want to start with seeds, watermelon transplants can also be purchased. Once the vines reach a certain size they often require pruning and turning to promote growth. When the melons are ready to be picked (check below to determine when they are ripe), use a knife to cut them off the vine instead of simply pulling the fruit, which can damage the plant.
Buying watermelons
It can be rather difficult to determine if the whole watermelon in the supermarket is ripe, but there are some tips to help choose a good one. First, make sure the melon is not damaged by checking the rind for bruises or cuts. Second, check the “ground spot” of the fruit. This is the area where the melon rested on the ground. Ripe melons have a yellow spot while unripe ones have a white one. Ripe melons also may have a rough rind or may have small ribbed indentations on the skin. Some say that ripe melons should produce a soft hollow sound when struck with the fingers instead of a harder, metallic one.
Purchasing cut watermelon is slightly easier. Just look for firm, brightly colored flesh. Generally the more color the flesh has the sweeter the fruit will be.
Once at home, store cut watermelon in the fridge for only a couple of days before eating. Whole watermelon can be stored in a cool place for up to two weeks.
http://www.uga.edu/vegetable/watermelon.html
http://www.museums.org.za/bio/plants/cucurbitaceae/citrullus_lanatus.htm
http://aggie-horticulture.tamu.edu/PLANTanswers/publications/vegetabletravelers/watermelon.html