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Guide to Watermelon Production


Watermelon is a fruit that grows on a vine-like flowering plant native to Southern Africa. It was cultivated in the Nile River Valley, in Egypt, and eventually in China, roughly 1,000 years ago. Now, watermelon is grown around the world. It is specifically selected to grow larger and juicier, resulting in the huge fruits that many of us are familiar with. The green outer rind is hard and fleshy, and rarely eaten, while the interior is soft, red or pink flesh containing the many seeds; this is the part of watermelon which is typically eaten.

So how does watermelon grow? Here is a guide for watermelon lovers.

  • Information on Watermelon
    • Species: Citrulus lanatus
    • Family: Cucurbitaceae family
    • Origin: Southern Africa

Watermelon is monoecious (both male and female flowers are produced on the same plant.


  • Climatic requirements: Optimum germination temperature: 27 – 32ᵒC, with night temperature not lower than 24ᵒC.
  • Optimum growth temperature: At night, 18-20ᵒC and day 24-30ᵒC and for ripening, 15-25ᵒC.
  • Soil requirements: Watermelon can be grown on a wide-range of soil types although sandy soils are preferred. The highest yields will generally be produced on well-drained sandy loam soils. Heavy clay soils, soil with obstructed drainage or very shallow soils should be avoided. Soil pH: 5.8 – 6.2. It is recommended to lime soil with pH values below 5.5.

Product Types

  • All sweet type: cylindrical and elongated fruit with a medium-green and dark-green striped rind and bright red fresh.
  • Crimson sweet type: Oval to round fruit with deep red/pink fresh and pale green and medium-green striped rind.
  • Super small type: Small fruit with very small seeds. These varieties have exceptional flesh quality and color. Fruit varies from round to oval in shape.
  • Seedless: Available with red, orange or yellow flesh and various rind patterns.
  • Recommended variety in the Philippines: The Sweet 16 F1 is a new generation variety of watermelon that can be planted in any season of the year. It has striped green color of watermelon that brings high yield and better fruits. It has good adaptation in off-season condition, like seasons in the Philippines. The round fruits weigh 5-6 kg with a crispy and very sweet flesh.

Soil preparation

  • Must be thoroughly and deeply cultivated to obtain a good root system.
  • It will allow optimal use of moisture and helps to prevent soil-borne diseases.
  • Roots develop at a depth of 30-40cm
  • Soils must be free draining to below 1.2m
  • Advisable that plants are grown on raised beds of at least 10cm high.
  • Beds should be 1.8m to 2m apart and as wide as possible on top.
  • Paths should be at least 60cm wide.
  • Planting periods. Watermelons are mostly planted in the summer months with limited planting during the rainy season.
  • Seedling production. The seed is sensitive to very specific conditions during germination, as the tiny embryo is contained in a relatively large, hard seed coat. Temperature and moisture control is crucial to success and too much moisture during germination can kill the seed.
  • Transplanting seedlings. Seedlings must be transplanted and watered as soon as possible after they have been obtained from the nursery. When transplanting, roots should not be damaged by application of unnecessary pressure around the root module. Soil should be watered into contact with the roots rather than pressed in.
  • Watermelon is generally grown in rotation with other crops, so it basically necessary to use manure or any soil improving crop to maintain organic matter in the soil. Applying side dressing of nitrogenous fertilizer is needed to avoid yellowing color in the plants.


  • Stage 1. Sowing to emerge. Irrigate with plan water to field capacity, to a depth of at least 1m before sowing/transplanting.
  • Stage 2. Emergency to first fruit set. Plants should be watered more heavily at a lower frequency prior to fruit set.
  • Step 3. First fruit set to harvest. During fruit enlargement, irrigation should be frequent and light. Irrigation should be reduced or stopped 7 days prior to harvest.

Watermelon has separate male and female flowers on the same plant and bees are needed for pollination.

  • Pest management. Treat the watermelon seeds with appropriate organic fungicides to minimize early development of diseases in the field. Dust or spray the young plants regularly with suitable organic insecticides as soon as the leaves have spread. During the seedling stage, watermelons are easily attacked by insect pests.
  • Harvesting. Harvesting occurs 11-17 weeks after planting. Watermelons should be harvested in the early morning as hot fruit respire much more rapidly and lead to over-ripe fruit on delivery. Cut the stem about 2-4 cm long as the longer stems make it more difficult for rots to enter the watermelon. Watermelon maturity can be determined by a combination of indicators:
  • External fruit rind color
  • Buttery yellow color of the ground spot
  • Various stages of floral leaf and tendril dying out
  • Dull sound when thumped
  • Slight cracking sound internally, when whole fruit are pressed.


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