Anna Sara Hill, Horticulture Extension Agent
Have you ever contemplated how that juicy watermelon on your table was grown; or have you wondered how the grower knows when it is the right time to pick it? Keep reading to learn the answers to these questions and more.
Traditionally, seeds were sewn directly into the field. Nowadays, most watermelon seeds are planted in greenhouses, and plants are transplanted into fields. Watermelons are grown in raised beds covered with black plastic. The plastic keeps the soil warm early in the season, allowing the plants to establish more quickly. After the vines grow out, the large leaves cover the plastic and provide enough shade to protect the fruit set and prevent the dark plastic from baking the roots during the hottest part of the growing season.
Watermelon plants require large quantities of water and fertilizer. Drip tape is run down the side of the bed underneath the plastic. Drip irrigation puts the water directly in the root zone, where the roots can readily utilize it. Other benefits of drip irrigation are the reduction of evaporation and the reduction of the spread of foliar diseases. Growers can also fertigate through the drip system and apply some pesticides.
Seedless watermelons are sterile. A Female flower only produces watermelon if it is pollinated by a male flower from a seeded watermelon. Therefore, both types must be planted in a field. Generally, the pollenizers are planted every 3rd row or every 3rd plant to ensure good cross-pollination. The blooms are dependent on bees and other pollinators to spread the pollen. Another complication is that the blooms open at sunrise and close at sunset, leaving a short time frame for the bees to do their work. Female flowers require between 500 and 1,000 grains of pollen for proper pollination, which requires multiple visits by the bees.
Diseases are the main problems that affect SC watermelons. Many diseases are weather-dependent, and disease pressure is variable between years. Insect pests can also create problems during the growing season. Some species cause direct damage by feeding on vines and fruit, and others cause indirect damage by transmitting viruses.
Growers must stay vigilant and scout for disease and insect issues throughout the growing season. Issues need to be treated early before they become widespread problems. As soon as vines grow off the plastic, growers should begin spraying to protect them from disease and insects. Rotating different chemistries and modes of action and applying recommended rates reduces the development of pesticide resistance. These treatments, called cover sprays, must continue through the end of harvest.
Telltale signs that fruit is ready for harvest is that the vine closest to the watermelon turns brown or starts to crack. The curly tendril connecting the melon to the vine will also turn brown and wither. Unlike other fruits that can be picked slightly unripe and then left to ripen on the counter, watermelons immediately stop ripening as soon as they are separated from the vine. This means it is important to ensure the melon is at the correct stage or ripeness before picking it. As the watermelon ripens. the field spot (which is the spot where the melon rested on the ground) should turn from a white or cream color to dark yellow. A perfectly ripe watermelon will turn from a shiny green into a dull green. When watermelons appear close to ripeness, the grower will test the percent brix with a refractometer. The brix is a measurement that correlates with how sweet a watermelon is. As the watermelon ripens, it gets sweeter, so the brix can be a good indicator of the level of ripeness.
Finally, the watermelons are ripe and ready to pick. The vines are turned for harvest, exposing the watermelons to crews that go through a field by hand to pick the ripest melons. Truckloads of melons are taken directly to fresh markets or a packing shed. At the packing shed. The watermelons are graded and packed for shipment to grocery stores, where consumers purchase them and take them home to prepare for their table.
Next time you cut up a watermelon and set it on your table, take a minute to reflect on how that watermelon grew and the effort, time, and care the grower put into growing the perfect watermelon. I think you will agree that what seems simple at the outset is a complex journey from seed to the table.
If you are interested in the history of watermelons, read “The Journey of a Watermelon: From Weed to Commercial Cultivation” in the Bamberg newsletter.
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