With care, watermelons will thrive in desert

KINGMAN - Can you actually let summer go by without at least one watermelon?

Watermelon is the No. 1-selling melon in the U.S. It's no wonder; this sweet, juicy, red melon is not only tasty but loaded with nutrition. It is high in Vitamin C and Vitamin A, also contains potassium, protein and dietary fiber. Watermelon is also high in lycopene, second only to tomatoes. Recent research suggests that lycopene, a powerful antioxidant, is effective in preventing some forms of cancer and cardiovascular disease.

According to research conducted at University of North Carolina at Chapel Hill, men who consumed a lycopene-rich diet were half as likely to suffer heart attack as those who had little or no lycopene in their diets.

A long history

Watermelons are believed to have originated in South Africa. It is not known when they were first cultivated, but there is evidence of them being grown in the Nile Valley as early as the second millennium B.C. Numerous seeds were found in Pharaoh Tutankhamun's tomb.

By the 10th century, it was being cultivated in China, the world's largest producer today. French explorers found the Native Americans growing watermelons in the Mississippi valley, other records show them being grown in Florida in 1664, the Midwest in 1673, in Connecticut in 1747, and in the Colorado River area in 1799. Some historians believe they were introduced to the U.S. by the African slaves.

Watermelons prefer well-drained, sandy loam soils which are slightly acidic, and a pH in the 6.0 to 7.0 range. Watermelons will also do well in other types of soil as long as adequate water and good drainage is available. However, fruit size and quality may be adversely affected in heavy clay soils. Good drainage is essential in any soil to prevent root rot.

Planting choices

They should be planted when the soil is warm and after any danger of frost has passed. They can be direct-seeded or started in trays and transplanted. When they are direct-seeded, it is recommended to over-seed and pinch out the weak seedlings.

Commercial growers have taken to transplants, mostly due to the increasing cost of seeds. In particular, the seedless varieties are primarily transplanted because of the high seed costs and because they tend to be harder to establish than the seeded varieties when direct-seeded.

Seedless watermelons are self-sterile hybrids that develop a normal-looking fruit with no fully developed seeds. The seeds for growing them are produced by crossing a normal diploid (a cell or organism with two sets of chromosomes) watermelon with one that has been genetically altered to the tetraploid (a cell having four times the number of chromosomes) state. The seeds from this cross produce plants, when pollinated by normal plants, that produce seedless melons. For pollination necessary to set fruit, normal seed types must be inter-planted with seedless melons.

The pollinator should be distinct from the seedless cultivar in color, shape or type so that the seedless and seeded melons in the patch can be separated at harvest. Flowers develop on watermelons at the ratio of about seven to 10 male flowers to one female. Because insects, usually bees, are the pollinators, without them you will have poor, if any, fruit. A single watermelon plant seldom produces more than one or two marketable melons.

Watermelon vines require considerable space and moderate amounts of nitrogen, phosphorus and potassium. Since they are a long season crop, many nutrients can be leached from the soil, especially sandy soils, so it is recommended a second application of fertilizer is added during the growing season.

Beware of stress

Irrigation is generally necessary for consistently high yields and quality because of the plant's limited root depth and because of the lack of water-holding capacity in sandy soils. Water deficits during establishment reduces plant vigor and may delay maturity. Water stress in the early vegetative stage may reduce leaf area and decrease yield. The most serious result from water stress is during flowering and fruit development.

There are approximately 100 varieties of watermelons commercially produced in the United States. You have your choice of red, yellow, orange or bright canary, your choice of size from 3 to 45 pounds, and your choice of shape.

When is it ripe?

The hardest part is knowing how to select a ripe watermelon or knowing when it is ready to be picked. Try using a combination of the following indicators: (1) light green, curly tendrils on the stem near the point of attachment of the melon usually turn brown and dry; (2) the surface color of the fruit turns dull; (3) the skin becomes resistant to penetration by the thumbnail and is rough to the touch; and (4) the bottom of the melon (where it lies on the soil) turns light green to a yellowish color. If it is white or pale green, the melon is not ready.

These indicators for choosing a ripe watermelon are much more reliable than "thumping" the melon with a knuckle. Many watermelons do not emit the proverbial "dull thud" when ripe. For these, the dull thud may indicate an over-ripe, mushy melon.

Once picked, uncut watermelon can be stored about two weeks if the room temperature is about 45 to 50 degrees. Uncut watermelons have a shorter refrigerator life, so store at room temperature until ready to chill and eat. Tightly cover cut pieces and store in the refrigerator for two to three days.