Watermelon (Citrullus lanatus) is a large vine vegetable grown throughout the United States. Indeed, the vegetable constitutes an important cash crop in a number of states. In 2000, watermelon production impacted the Texas economy to the tune of $160 million. Watermelon can be grown in all parts of the United States, though the vines prefer warm climates. The answer to the question "Is the watermelon perennial?" is simple: No. An examination of its growth traits reveals the true nature of the vegetable.
Growth habit describes the manner in which a plant grows. Watermelon expresses true annual growth. True annuals comprise a group of plants that experience their entire life cycle in the course of a single growing season. Perennials, on the other hand, persist throughout multiple growth seasons while continuing to fruit and flower. Although numerous varieties of watermelon exist, from cold-hardy early fruiting cultivars to seedless, late-blooming hybrids, all express the same growth habit.
Watermelon vines are hermaphroditic. Male blooms appear first in spring or summer, before the fruit. Female blooms follow, with fruit. Regular watermelons, non-hybrid or cultivar varieties, produce fertile seeds through which they self-propagate. Established watermelon patches may persist for many generations and a number of years through self-propagation, or natural reproduction; they reoccur year after year, though each year's growth constitutes a new generation of plants, making them annuals.
Gardeners propagate watermelon through seed or transplanting. Watermelon grows well from seed in warm regions with average spring and summer temperatures between 70 and 85 degrees. In cool regions, transplanting early-fruiting varieties produces an ideal crop. Early-fruiting varieties produce fruit earlier in the year than do standard watermelons and are suited for growth in cold regions because their fruit reaches maturity before the risk of frost arrives. Plant seeds 7 to 10 feet from one another.
Proper watermelon conditions, or growth, are required to ensure that the plant produces a new generation of growth with each passing year. Watermelon flourishes in warm soil with a pH range of 6.0 to 6.8. Though the plants tolerate various soil types, they prefer sandy loam. Seeds can experience difficulty germinating in soil cooler than 60 degrees Fahrenheit and should only be planted after the last frost of the early spring. Mixing black plastic mulch with the planting soil increases the soil's warmth for the benefit of the plants while decreasing the likelihood of competitive weeds arising around the watermelon. Ohio State University horticulturalist Ted W. Gastier recommends adding 1 pound of nitrogen, 2 pounds of phosphorus (P2O5), and 3 pounds of potash (K2O) per 1,000 square feet as fertilizer. Watermelon roots grow deeply and plants only require watering during periods of drought.
Watermelon Pests and Diseases
According to "The Encyclopedia of Fruit & Nuts," watermelon suffers a number of fruit, leaf and root pests and diseases that inhibit species propagation and productivity. Common watermelon pests and diseases include root knot nematodes, cucumber beetles, flea beetles, grasshoppers, melon aphids, spidermites, maggots, watermelon mosaic virus, tobacco ringspot virus, southern blight and bacterial fruit blotch. Careful attention, proper maintenance and regular soil testing help prevent such problems.
If watermelon crops fall victim to disease or pests, plants decline in health and die quickly; a crop may not last one full year. To ensure optimal fruit production during annual growth and persistent generations of plants, keep the specimens free of pest and disease.