Learning about crops - Watermelons

I've grown watermelons for two years now.  In the first year (2011), we did the old tried and true method of letting the runners splay out wherever they please.  This past year, however, we trellised the watermelons.  I built an angled trellis out of 2x4's, 2x3's, conduit, and wire fence material.  Watermelon starters were planted at the base of the trellis with the vines trained upward.  I deliberately chose a smaller variety of watermelon that wouldn't put as much strain on the tendrils from the weight of fruit.  Once the fruit became sizable, I made a melon sling out of women's panty hose to help support the weight until it was time to pick.

Companion Plants
Companion plants for watermelons are the marigold (deters beetles), nasturtium (deters bugs and beetles), and oregano (general pest protection).

Growing Watermelons
Melons like nutrient-rich soil with a pH between 6.0 and 6.5.  General fertilizers work just fine.  They like an air temperature at least 65 degrees, warmer is preferable.  As you'd imagine by the plant name, they need a lot of water.  The plants double in size in the month of July. 

Insect Pests
Cucumber beetles typically prefer cucumbers and muskmelons, but they will occasionally feast on watermelons, too. Insecticidal soap is a safe, effective treatment for most cucumber beetle infestations. If you've endured major cucumber beetle attacks in the past, keep them from getting to your vines with row covers—just be sure to remove the covers when the vines begin to flower so that bees can pollinate them, which is necessary for the plant to set fruit. Spraying young plants with kaolin clay may deter beetles from feeding.

Squash vine borer larvae tunnel into watermelon vines, chewing inner tissue near the base and filling the stem with moist, slimy castings. The attacked vines wilt suddenly and girdled vines rot and die.

From organicgardening.com

Squash vine borers, which are most damaging to winter squash, look like 1-inch-long white caterpillars. They tunnel into stems and can go undetected until a vine wilts. Keep a constant lookout for entry holes at the base of the plants, surrounded by yellow, sawdustlike droppings. Cut a slit along afflicted stems and remove and destroy the larvae inside, or inject the stems with Btk (Bacillus thuringiensis var. kurstaki). Hill up soil over the stem wounds to encourage the plant to sprout new roots there.

To prevent borer damage, keep an eye out for the adult borer, a wasplike orange-and-black moth; it lays eggs at the base of the stem in late June or early July in the North, or in April to early summer in the South. During these times, check the base of the stems and just below the surface of the soil regularly for very tiny red-and-orange eggs. Rub the eggs with your finger to destroy them.

How to Tell When a Watermelon is Ripe
Here are a few ways to tell when a watermelon is ripe.

• The little tendril at the point of attachment turns brown and dries up. In some melon types, the tendril dries up a week before the melon is actually ripe.
• Rinds of unripe watermelons have a shiny gloss.  Ripe melons don't have the shine so the rinds have a dull appearance.
• The fruit produces a dull, muffled "thud" sound when thumped, rather than a sharp or metallic one.

Nutritional Information on Watermelons

Watermelons are a "good source" (10-19% of RDA) of Vitamin A.  There are also notable quantities of Lysine, Threonine, Tryptophan, Magnesium, Potassium, Copper, Manganese, Vitamin B6, Thiamin, Pantothenic Acid.