Watermelon

Harvests generally begin about 30 days after full bloom and continue for several weeks with 3 to 4 cuttings at 3-to-5-day intervals. Ripeness in watermelon is difficult to determine because the fruit remains attached to the vine, rather than 'slipping' off. The flesh of a typical red-fleshed watermelon changes from immature pink to red-ripe, and then to overripe within a 10-to-14 day harvest window. Overripe fruits have a watery, mushy texture and lower sugars. Rind color changes indicating maturity, if any, are specific to cultivars. 'Golden Midget' turns yellow as it ripens, and 'Sugar Baby' becomes dark green and loses its stripes. Generally, however, the only indication of ripeness is that the tendrils of the leaf closest to the fruit attachment become dry. Additional ripeness indicators include a change in ground spot color from greenish-white to pale yellow. The rind becomes hard to pierce with the fingernail and the blossom end 'fills out'. When ripe, there is also a 'bloom' or powdery coating giving the fruit a duller appearance and a rough feel. Although researchers are experimenting with various nondestructive gauges of fruit soluble sugars, at this point the usual method for timing the start of watermelon harvest is to cut open a few representative melons in the field.

In addition to the difficulties of timing harvest, there are a number of other problems associated with watermelon harvest. If the field has received abundant water, the watermelons may crack open, especially if harvested in the morning when full of water (turgid). The risk of cracking can be reduced by harvesting in the afternoon and by cutting the stem rather than pulling the fruit off. Stacking watermelons on the side, rather than on end, also reduces the risk of cracking.

Cut watermelons must be shaded to minimize additional heat buildup and because direct sunlight after harvest (especially on the groundspot) reduces watermelon quality. If plants are not too turgid, field heat can also be minimized by harvesting in the morning. Watermelons should be dry when loaded, however, rather than dew-covered. They are either bulk loaded into straw-padded trucks, or placed in multiwalled corrugated fiberboard bins holding 60 to 80 melons and weighing 1,100 to 1,200 pounds fully loaded. Transit temperatures should be 45 to 50 degrees F.

Watermelons are stored at higher temperatures and lower humidity than muskmelons (50 to 60 degrees F, 90 percent relative humidity). Storage for prolonged periods below 50 degrees F can lead to chilling injury; e.g., one week at 32 degrees F can cause pitting, color loss and off flavors. At 50 to 60 degrees F, they can be kept 2 to 3 weeks after harvest. Even within this range, however, the red color is gradually lost. Although watermelons do not ripen off the vine, flavor and color in seeded (but not seedless) watermelons will improve over 7 days holding at room temperature.