University of Maryland Extension

Watermelon

Watermelon

Watermelon (Citrullus lanatus) can be both the fruit and the plant of a vine-like (scrambler and trailer) herb originally from southern Africa and one of the most common types of melon. This flowering plant produces a special type of fruit called a pepo, a berry which has a thick rind and fleshy center. Pepos are derived from an inferior ovary and are characteristic of the Cucurbitaceae family. Loosely considered a type of melon, the fruit has a smooth exterior rind (green, yellow and sometimes white) and a juicy, sweet interior flesh (usually pink, but sometimes orange, yellow, red and sometimes green if not ripe). Watermelon contains about 6% sugar and 92% water by weight. As with many other fruits, it is a source of vitamin C. Rinds are also edible and contain many nutrients. In China, they are stir-fried, stewed, or, more often, pickled.

Planting

Direct sow the seeds in a sunny, well-drained area when all danger of frost is past and the soil is warm. Sow in raised hills or rows 3 inches high. Thin to 3 plants per hill 3 feet apart, or 1 plant per foot in rows.  For earlier fruit, start seeds indoors. Wait till the ground warms up, before transplanting, at least 15 days after last frost. For extra-early crops, growers use black plastic over each row, with the edges covered. Plants are transplanted through holes. Space plants 2 feet apart in rows 8 feet apart. Midget types can be planted 1 foot apart in rows 6 feet apart.

Cultivation

  • Fertilizing – Incorporate fertilizer into soil at planting, or water with a week fertilizer solution. Fertilize again when plants begin to set fruit with fish-emulsion spray or compost tea or side-dress each plant with 1/4 lb. of 10-10-10 fertilizer or equivalent.
  • Weeding – Cultivate the soil deeply prior to planting. Mulch with straw, salt hay, or compost.  Alternatively, cover ground with black plastic to prevent weed germination.
  • Watering – Make sure plants get at least an inch of water per week at the beginning.  Unless a prolonged dry spell strikes, stop watering when the fruits begin to ripen. If they don’t get too much moisture during the last week or two, the fruits will have better flavor.
  • Special directions – Some people prefer to grow seedless varieties, which require a seed variety nearby for pollination. Honey bees and other pollinators will cross-pollinate for you.

Common Problems

Harvesting  

Watermelon can be harvested in 68 to 95 days from planting, depending on variety. The rind on the underside of the melon will turn from white to pale yellow.

Storage and Preservation  

Will keep for 5 to 18 days in cool (32° to 50°F), moist (90% Relative Humidity) conditions. Refrigerate and cover once melon is cut.

 

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