General Information and Agronomic Aspects
The watermelon is often large enough that groceries often sell half or quarter melons. There are also some smaller no more than 3 kg, spherical varieties of watermelon, both red- and yellow-fleshed, sometimes called "icebox melons" or "mini watermelons"
Nutritive Value per 100 g of edible Portion
|Raw or Cooked Watermelon||Food|
(Calories / %Daily Value*)
(g / %DV)
(g / %DV)
(g / %DV)
(g / %DV)
(mg / %DV)
(mg / %DV)
(mg / %DV)
|Vitamin B 6|
|Vitamin B 12|
(mg / %DV)
(mg / %DV)
(g / %DV)
|Watermelon, raw||30 / 2%||7.5 / 3%||0.2 / 0%||0.6 / 1%||7.0 / 1%||11.0 / 1%||0.2 / 1%||112 / 1_%||569 IU / 11%||8.1 / 13%||0.0 / 2%||0.0 / 0%||0.0 / 2%||0.0 / 1%||0.3|
*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.
|Square watermelon in Japan|
(c) Laughlin Elkind, wikipedia
A watermelon contains about 6% sugar and 92% water by weight. As with many other fruits, it is a source of vitamin C. Notable is the inner rind of the watermelon, which is usually a light green or white colour. This area is edible and contains many hidden nutrients that most people avoid eating due to its unappealing flavour. Watermelons contain a significant amount of citrulline whose beneficial functions are now being unraveled. Among them is the ability to relax blood vessels, much like "Viagra" does to treat erectile dysfunction and maybe even prevent it. Scientists know that when watermelon is consumed, citrulline is converted to arginine through certain enzymes. The citrulline-arginine relationship helps heart health, the immune system and may prove to be very helpful for those who suffer from obesity and Type 2 diabetes (Texas A & M University, 2008).
- "Charleston Gray" (open pollinated, matures in 55-60 days, rind colour is light green with light stripes, deep red flesh colour, fruit shape oblong, fruit weight 10-16 kg, tolerant to Fusarium wilt and anthracnose, excellent for shipping, popular in Kenya)
- "Congo" (matures in 90 days, round melons reach 16 kg, green stripes, sweet red flesh and thick rinds)
- "Crimson Sweet" (open pollinated, matures in 90-120 days, rind colour light green with broad dark green stripes, flesh colour brilliant red, fruit shape blocky oval, fruit weight 7-9 kg, high yielder and good shipping qualities, resistant to extreme heat, popular in Kenya)
- "Moon and Stars" (matures in 95 days, dark green skin with yellow spots resembling moon and stars in the night sky, melons weigh 9-18 kg, pink to red flesh)
- "Orangeglo" (matures" in 90 days, very sweet and crisp, oblong-shaped melons 9-14 kg, bright orange flesh with off-white seeds)
- "Sugar Baby" (open pollinated, matures in 60-75 days, rind colour greenish black, flesh colour deep red, fruit shape round, fruit weight 7-8 kg, very popular in Kenya, suitable for shipping and long transport)
- "Sunday Special" (seedless variety, rind colour dark green with black stripes, flesh colour red, fruit shape oval, fruit weight 6-10 kg)
Because varieties and market trends change all the time, consult your local seed company, buyer or extension officer for the latest information on the available varieties.
|Watermelons displayed in a Nairobi supermarket. Crimson Sweet in stripes & Sugar Baby dark green.|
(c) A.A. Seif
|Sugar Baby watermelons in a trolley in a Nairobi supermarket|
(c) A.A. Seif
(c) A. A. Seif
Notice, that on some of the Sugar Baby melons there are yellow patches where the melon has rested on the ground. When this patch turns yellow it means the watermelon has reached maturity. It is not wise to harvest much before the patch turning yellow, as unripe watermelons are such a disappointment to buy.
Watermelons can grow at altitudes of up to 1500 m, Best growing areas are the lowlands with high temperatures and relatively low rainfall where irrigation may or may not be necessary
They grow best under hot temperatures. They do well at temperatures of between 22 and 280 C. Stagnation of growth occurs at temperatures less than 150 C.
Watermelon production is suited in low to medium rainfall areas with additional irrigation. Optimum rainfall requirement per cropping season is 600 mm and 400 mm is considered minimum. Excessive humidity may favour leaf diseases and also affect flowering.
Sites and soils:
Watermelons grow best on sandy loam soils which are well drained and slightly acid. When planted on very heavy soils, the plants develop slowly, and fruit size and quality are usually inferior. Fine sands produces the highest quality melons when adequate fertiliser and water are provided. Windbreaks are advisable on sandy soils to reduce "sand blast" damage and stunting to young seedlings during strong winds. To reduce the risk of diseases, do not plant on land where cucurbits have grown during the past three years. Well drained heavy soils can also be used. The soils should be rich in organic matter. Watermelon is fairly tolerant to soil pH as low as 5.5. However, a slightly acid soil with a pH of 6.0 to 6.5 is ideal.
Watermelon is propagated by:
- Seeds, directly planted in the field.
- Transplants: there is a trend towards greater use of transplants by commercial growers because of the precise requirements for seedless (triploid) watermelon seed germination and the uniformity of the resulting crop. Instead of planting directly in the field and have 3 weeks of accumulated weeds germination and insect attacks to battle with, planting of seeds in seed trays in a protected area for later transplant into the field when at least 2 permanent leaves have developed, is a very viable option. Seed trays of various design and cost are widely available from seed merchants.
- Watermelon is grafted in some production areas, most notably in Japan and Korea, where nearly all of the plantings utilise this technique. Grafted watermelon also is widely used in China, Spain, and Italy. Grafting on to rootstocks resistant toFusarium oxysporum and those tolerant of cold soils are the primary reasons for grafting. Popular rootstocks for watermelon are bottle gourd (Lagenaria siceraria), interspecific hybrid squash (Cucurbita maxima x C. moschata), or wild watermelon (Citrullus lanatus var. citroides). Commonly used grafting methods for watermelon are hole insertion, tongue approach, and cleft. With the ban on the use of the broad-spectrum soil fumigant methyl bromide, it is likely that grafting will be used even more in the future and for more uses other than those already invoked. Grafted watermelon plants produce fruit with firmer and redder flesh over a longer period of time. The grafted watermelons produce more fruit per plant with better quality to justify their higher cost. Grafted watermelon, particularly on interspecific hybrid squash rootstock, can grow on soils with higher salt concentrations than non-grafted watermelon can tolerate.
The holes are dug at a distance of about one metre within the row and about 2 metres between the rows. Plant 2 seeds per hill, placing them 3 to 4 cm (1.5 inches) deep into the soil. Water the hills thoroughly if there is no rain. At 25-30 cm high earthing up around the plant bases is recommended to prevent exposure to the sun.
Watermelons, pumpkins, cucumbers, and zucchinis can be planted side by side. Cross-pollination can occur between cultivars of the same crop (e.g. watermelons and watermelons) but not between different crops (e.g. watermelons and pumpkins). Bees are necessary for pollination. Bees need to be present and active in the crop. If bees are not plentiful, then place at least 2 hives/ha, spreading them around the field perimeter and check to ensure that male flowers are producing pollen. Flowers are most receptive to pollination during the morning hours when bee activity is usually the highest. Bee activity is related to climate and is lower in cooler weather. Spraying and irrigation should be coordinated to occur when bees are least active
- After planting to allow fast and even emergence.
- At early bloom to prevent poor fruit set and misshapen fruit.
- During fruit development to ensure good melon size.
- Do not apply too much water, avoid waterlogging, and minimise wetting of the bed tops. Heavy irrigation or rainfall may also result in fruit splitting.
Weeding should be done regularly to keep the field clean. Avoid injuring the plants when weeding.
- A dull hollow sound when the fruit is tapped with the knuckles
- The change from white to cream or pale yellow of the skin area where the melon has been resting on the soil.
- Shrivelling of tendrils on nodes to which melons are attached.
- Slight ribbing on surface of fruit can indicate maturity in some varieties.
- The Brix test is the most objective way of testing maturity. It assesses the total soluble solids (soluble solids is related to sugar content and is an indicator of sweetness) of the melon flesh. The test is becoming more popular with many retailers insisting on specific brix levels particularly in seedless varieties.
Internal cracking is caused by cool temperatures during early fruit-filling period. Other influences are stop-start growth, excess nitrogen, low boron levels, or heavy infrequent watering at fruit fill. Affected melons tend to be flattened in shape and feel lighter than usual.
Spongy end occurs in melons, which have been poorly pollinated. These melons may turn yellow and drop off the vine early in their development or partly develop with the stylar end soft and spongy. This area is also slightly pointed. Internally, there is very poor seed development at the spongy end.
White heart is white streaks or bands of undesirable flesh in the heart (center) of the fruit. This is caused by excessive moisture (and probably too much nitrogen) during fruit maturation.
Hollow heart is a disorder that varies among varieties. Causes are unknown.
Sunburn occurs most frequently in varieties that have dark green rinds. "Charleston Gray" types and other melons with grey-green rinds rarely sunburn. Good healthy foliage will minimise sunburn as well as favour good yields and quality. Strong winds can blow unprotected vines away from the developing fruit along the edges of the rows and cause full exposure of the fruit to the sun.
Rind necrosis is an internal disorder of the watermelon rind. Symptoms are brown, corky, or mealy textured spots in the rind which may enlarge to form large bands of discolouration that rarely extend into the flesh. Experienced pickers often can detect affected melons by the subtle knobbiness that is visible on the surface of affected melons. The cause of rind necrosis is unknown. Bacterial infection has been reported to be a cause, although similar bacteria are found in healthy melons. Drought stress also is reported to predispose melons to rind necrosis.