How to Grow Watermelon Plant from Planting to Harvest

Stages of Growing Watermelon

 Homegrown watermelon freshly diced
Homegrown watermelon freshly diced

Watermelon is a delicious, refreshing, and hydrating fruit. We will look at growing watermelon. Originally from Africa, watermelon is cultivated and grown in many countries all over the world.

Growing watermelon successfully will involve the following stages namely:

  1. Location for planting/growing watermelon
  2. The season and climate for planting watermelon
  3. Soil test for watermelon planting
  4. Soil preparation for growing watermelon
  5. Planting watermelon seeds and pre-germinated young shoots
  6.  Watermelon care
  7. Harvesting watermelons
  8. Storage

Location for Planting and Growing Watermelon

The first step in how to grow watermelons is finding a suitable location. It is important to choose the right area to plant watermelons so that the conditions will be favorable for the plants to do well. The vines of the plant can grow up to twenty feet long so an area with an ample amount of space will be needed. Since watermelon needs a large space to grow, it should not be planted among or near most plants. The vines may wrap themselves on stems and leaves of other plants that may become choked out. It is also important to choose an area that will be exposed to a high level of daily sunshine as growing watermelons require a lot of sunlight to thrive.

The Season and Climate for planting watermelon

Healthy watermelons and vines
Healthy watermelons with vines

Another important stage in how to grow watermelons is knowing the favorable season and climatic conditions for the plant to do well. Planting watermelon at the wrong time of year or in unsuitable climatic locations will likely result in poor yield, plant death, or even failure to germinate. The correct time to plant watermelons is around late spring to early summer; which is when the soil temperature is at least 70°F (21°C). Watermelon needs heat to thrive so it will not grow in very cold areas. Furthermore, if it is late in the season, indoor germination and early growth in biodegradable pots or containers to later be moved outside is an option.

Soil Test for Watermelon Planting

To grow watermelon successfully, the soil needs to be tested to ensure the acidity, temperature, and other conditions are okay for the cultivation. The soil temperature should be at least 70°F (21°C). The soil should be tested to confirm if it has the correct pH of between 6.0 to 6.8. This is to ensure that there is sufficient calcium in the soil. The soil should be nutrient-rich but needs to be well-drained so that water does not collect around the watermelon plant.

It is best to wait for at least two weeks  after the last frost in the area before planting watermelons

Soil Preparation for Growing Watermelon

Raking the soil in preparatIon for cultivation
Raking the soil in preparation for cultivation

The ideal soil for growing watermelons is loose, well-drained but moisture-retentive soil that is rich in organic matter. If the soil is lacking in organic material, mulching, application of manure, or aged compost can make all the difference. In temperate regions where the soil may be colder than the recommended temperature, the soil can be warmed by covering it with black plastic before planting.

An area of at least 4×6 feet (1.2×1.8m) is needed to grow the melons. This is the smallest space sufficient for plant beds for growing watermelons. Sticks rocks and other unwanted objects should be removed from the vicinity. The soil will need to be tilled.

Create mounds of dirt in the plant bed. Each mound should be approximately 1 foot (0.30m) (30cm) high, and between 2 to 3 feet (0.61 to 0.91m) (60 to 90cm) wide. Leave about 1 to 2 feet (0.3 to 0.6m) (30 to 60cm) of space between each mound. Space rows about 4 feet (1m) (120cm) apart to ensure the melon vines have plenty of space to grow.

Planting Watermelon Seeds and Pre-germinated shoots

A growing watermelon shoot
Growing watermelon shoot

How to Plant Watermelon

Planting using Seeds

Sow five to six seeds in each mound of earth. The seeds should be planted 4 to 6 inches, about (10 to 15cm) below the surface of the dirt mounds. If you are planting seedlings that were started indoors or bought already germinated from a nursery; then plant 2 to 3 seedlings per mound and saturate with water.

It is best to plant watermelon seeds indoors if it’s an area that has long winters and short summers as they will not survive cold weather. When the weather warms up they can be transferred outside provided they were planted in compost and peat containers.

The plant rows can be covered with floating row covers that help to preserve the heat while also protect the young seedling from pests. If young starters are planted, or you’re transferring them from indoors; it is still advised to still use some form of insulation to ensure proper development of the watermelon plant due to sufficient warmth.

Planting using Seedlings

Plants that were started indoors or some other shelter; have to be planted in pots or specially designed containers that are made from biodegradable material. These materials are readily absorbed by the soil. Therefore they can be inserted into a hole or depression in the ground along with the watermelon shoot. It will eventually dissolve safely into the soil and allow the plant’s roots to continue their growth unhindered. The roots of young plants like the watermelon are fragile and can easily be damaged if an attempt is made to remove it from a non-biodegradable vessel for transplanting.

Some of these biodegradable vessels that can be used to germinate and start the growth of watermelon plants are made from industrial and agricultural solid waste like; wood pulp, paper, and peat moss; and others from types of solid residue such as; wood fiber, coconut fiber (or coir), rice hull, manure, peat, soil wrap, and straw.

A trellis can be used to grow watermelon. It is a constructed framework of beams and bars that can support significant weight other than its own. It is useful in supporting climbing and creeping vines such as growing watermelon vines.

The trellis should be at least 8 x 8 feet (2.4m) wide or more. It should be well anchored into the ground; so as not to give way under the increasing weight of the growing watermelon. Spacing of the plants should be done at the base of the trellis 3 to 4 feet (0.9 to 1.2m) apart.

The watermelon vines should be trained up the trellis; they can be secured to the trellis with elastic garden tape or some other soft string. The growing watermelons will need to be supported with sturdy, but non-abrasive netting. that should also be fastened to the trellis.

Watermelon Care

Melon fruits among vine foliage
Melon fruits among vine foliage

There are various ways to care for watermelon plants. The following are simple ways to care for watermelons.

  • Mulching and Cover Cropping
  • Watering Watermelon
  • Fertilizing Watermelon
  • Pests and Diseases

Mulching and Cover Cropping

Protect the seeds with mulch, landscaping fabric, or row covers, especially in colder climates. Covering the area where the watermelon is planted with plastic mulch or black landscaping fabric will help to preserve the heat in the soil and keep the seedlings warm.

When the watermelon fruit begins to develop and is about the size of a tennis ball, some straw or other form of mulch should be placed underneath it; between the fruit and the soil to guard against the accumulation of moisture and micro-organisms that may damage it or cause rot.

Watering Growing Watermelon

Young growing watermelon fruit
Young growing watermelon fruit

Water the watermelon plants every two to three days throughout the summer.

Melon plants need at least one to two inches (2.5 to 5.1cm) of water per week.

Watering the melon plants with sprinklers and other overhead methods is not advised. The reason is that wet foliage can encourage the development and spread of fungal diseases and pests. soaker hoses or drip irrigation that deliver moisture to the base of the plant are the best methods of irrigation.

Water more often if the weather is hot and dry. Care should be taken not to overwater the watermelon plants as this can cause them to rot. If water is standing on top of the soil, some more mulch should be added around the melon plants to help absorb it.

How do I make my watermelon sweeter when growing?

To make watermelons sweeter when growing, water the plants less frequently as the melons begin to ripen, as this will allow the fruit to develop more flavor and sweetness.

Fertilizing Watermelon

Fertilize the watermelon plants weekly or every three to four weeks depending on the type and specification. Use a well-balanced fertilizer that can be purchased at plant nurseries and garden shops. The weekly application with a liquid soluble fertilizer should be nitrogen-based at the early stage with a (20-10-20) measurement. Once the watermelon plant’s flowers start blooming, the fertilizer should be switched to phosphorus and potassium-based ones (20-20-20) for the rest of the season.

Watermelon requires ample potassium and phosphorus for optimal melon production.

Homemade compost tea can also be made and used. Fertilizer compost is put in a container and sprinkled by hand. About 1 teaspoon (14.8ml) of the fertilizer in the dirt around each of the watermelon plants.

Pests and Diseases of Watermelon Plants

Disease destroying a mature melon fruit
Disease destroying a mature melon fruit

Two of the biggest threats to a successful yield after the cultivation of watermelon are pests and diseases. They can either partially or completely ruin/destroy the plant and the fruit.

Monitor plants for signs of pests and diseases. If the plants are being attacked by bugs and other insects, row covers, among other countermeasures can be used to keep them away.

Watch for any powdery white patches or spots on the leaves and stems of the plants. This is evidence of powdery mildew. If they are infected remove all the affected plant parts and spray the rest of the garden with a suitable fungicide or diluted copper spray.

The following is a list of the main pests and diseases that afflict watermelon plants and fruits:

Diseases of Watermelon
  • Foliar Diseases
  • Fruit Diseases
Foliar Diseases of Watermelon
  • Bacterial Fruit Blotch
  • Anthracnose
  • Gummy Stem Blight
  • Downy Mildew
  • Alternaria Leaf Spot
  • Cercospora Leaf Spot
  • Myrothecium Leaf Spot
  • Powdery Mildew
  • Leaf Mosaic
  • Fusarium Wilt
  • Tobacco Ring Spot Virus
  • Herbicide Injury
Fruit Diseases of watermelon
  • Bacterial Fruit Blotch
  • Anthracnose
  • Bacterial Rind Necrosis
  • Belly Rot
  • Diplodia Stem End Rot
  • Pimples
  • Cucumber Mosaic Disease
  • Blossom End Rot
  • Bottle Neck
  • Sun Burn
  • Fruit Cracking/Scarring
  • Splitting
  • Cross Stitch
Pests of Watermelon
  • Insect Pests
  • Animal Pests
Insect Pests of Watermelon
  • Foliage and Fruit Insects
  • Plant Sap Feeding Insects
  • Soil Insects
Foliage and Fruit Insects
  • Thrips
  • Flea Beetles
  • Two Spotted Spider mites
  • Cabbage Loopers
  • Beet Armyworms
  • Grasshoppers
  • Red Pumpkin Beetle
  • Leafminer Flies
  • Spotted and Striped Cucumber Beetles
  • Serpentine Leaf Miner
Plant Sap Feeding Insects
  • Silverleaf White Flies
  • Squash Bugs
  • Melon Aphids
Soil Insects
  • Click Beetle/Wireworms
  • Seedcorn Maggots
  • White fringed Beetles
  • White Grubs
  • Mole Crickets
Animal Pests of Growing Watermelon
  • Coyotes
  • Deer
  • Racoon
  • Groundhogs
  • Rats
  • Birds
  • Slugs
  • Snails
  • Nematodes

To get rid of aphids, spray a diluted insecticide on the plants early in the morning. Repeat as needed. If pests like the cucumber beetle are observed, set insect traps for them or apply a pyrethrins mix to the soil. Black plastic can also be used instead of mulch to protect the watermelon plants and keep insects away.

Harvesting Watermelon

Harvested watermelons
Harvested Watermelons

Harvesting is a very important stage in knowing how to grow watermelon plants; the reason being that after all the work put into cultivation and nurturing, the watermelon fruit can be damaged even at this stage; or harvested at the wrong time. The consequence of harvesting at the wrong time is that watermelons don’t continue to ripen after they have been cut from the vine. So if the melon is plucked when not yet ripe, then it will end up being wasted; however, on the flip side of the problem, the watermelon can go from unripe to spoiled in just a matter of days so they need to be checked frequently once they are approaching maturity.

How long does it take to grown watermelon?

It takes about 65 to 90 days to grow watermelon to a stage of ripening and harvesting. That means, it takes roughly 3 months for a watermelon plant to be planted and harvested. The approximate duration of a watermelon’s life cycle depends on the variety or species. Some watermelons are grown within a shorter period while others take time. Watermelons do not need a year to grow. In fact, if it is gardening where the watermelons are watered, you can grow watermelons up to 3 times a year. Depending on rainfall alone as the source of water for watering the melon plants means you can only harvest once or grow them once a year.

Once they are mature, watermelons ripen over a span of two weeks especially for fruits that are on the same plant; so when one is confirmed to be ripe, the others are not far behind. They will usually ripen within days of each other.

If the grower is able to determine the period prior to the melons ripening, the plants should only be watered when necessary; such as to keep the vines from wilting.

Withholding water during the late stages of the watermelon’s development causes sugars to concentrate in the fruit, and too much water will dilute it.

How to Tell if a Watermelon is Ripe

There are a number of ways to tell if a watermelon is ripe and ready for harvest. These methods are not necessarily based on scientific research, but on tested experiences and knowledge of previous growers.

An outline of the main established ways to tell if a watermelon is ripe and ready for harvest is as follows:

The color of the rind

The rind or outer skin of the watermelon is generally bright shiny green throughout its earlier development, but it turns to a dull hue when it begins to ripen. This change in the shade of color is quite obvious and noticeable particularly if the grower has been observing the melon fruits since their early growth.

The shade

The shade of color at the base of the fruit where it had been making contact with the soil. This is one of the best clues on how to tell when a melon fruit is ready for harvest. The watermelon should be carefully tilted or tipped slightly; this is to allow the grower or farmer to get a look at the part of the fruit that has been lying on the ground; care should be taken not to move, rotate or jerk it much as the vine can easily be damaged. The part that makes contact with the soil is usually pale/whitish green, or even straw yellow during the growing period; to a creamy yellowish hue when it is ripe.

The date of planting and germination

The date of planting and germination can be noted; since the approximate duration of a watermelon’s life cycle is known, (watermelons will be ready for harvest roughly 65 to 90 days after sowing depending on the variety) then the period of it starting its maturity can be estimated and noted on a calendar or a farming journal for reference.

The vine tendrils coloring and freshness

The vine tendrils are generally fresh, green, and curly during the growing and development of the melon plant; the ones closest to the stem begin to dry out, die and turn brown as the watermelon ripens. The leaf closest to that tendril should also be turning yellow or brown. If the tendril is still green and fresh, then the fruit is not ripe.

Pressing on the fruit

When pressed with a finger, if the fruit sounds or feels like it gave a little, then it is likely to be ready; and if it feels turgid, then it is not ripe. This method is not favored by many because of the potential damage pressure can do to the rind. Furthermore, a damaged rind can be an entry point for disease.

Rapping and thumping

Rapping or thumping lightly on the fruit is another unconventional but tested method of knowing if the watermelon fruit is ready for harvest. However, this method is dismissed by a few people as not being consistently reliable. They point out that it does not apply to all varieties; with some growers even stating that the sound of a dull, low pitched thud, the type that seems to be from a hollow object; (the sound that is the more widely accepted sign of a ripe melon fruit), with some cultivars, is an indication of overripe fruit.

It involves briskly tapping or rapping one’s fingers or hand lightly on several fruits that are known with certainty to be unripe and listening for the resonating sound from each one. This is to familiarise the farmer with the sound the unripe watermelon fruits make so that he will notice the difference when he hears the sound from the ripe one. The sound from tapping the unripe fruit is described as a dull thud; which gives the impression of a solid object or a vessel that is full of some form of matter. The sound from the resonation of a rap, tap, or thump on a watermelon that is ripe is described as a hollow-like sound.

Aroma at the stem

Ripe watermelon fruits will have a sweet aroma coming from around the stem.

Ripe fruit

A ripe watermelon noticed on a plant indicates that any others on that plant and others that are roughly the same age are also about to ripen.

The color at the top

When there is little contrast between the stripes of the watermelon and the color at the top, it’s an indication of ripening.

The blossom end

The blossom end of the melon will soften and have a sweet aroma when it ripens.

How to Store Watermelon

Harvested watermelons
Harvested and stored watermelons

The first and most important thing to ensure when storing watermelon; is the state and physical condition of each individual fruit. Any fruit that has any form of injury or damage to the rind is a risk to the rest.

Check for any splits, bruises, cracks, starting to soften, rot, or being overripe, on harvested watermelons. Anyone found to have such defects should be used immediately and not put into storage.

Freshly harvested watermelon fruit can last seven to ten days when stored indoors at room temperature in the range of 68 to 72° F.

Harvested watermelons keep for two to three weeks if they are at a location with a temperature of 52 to 60°F and 85 to 90% relative humidity. These conditions can be found mostly in basement storage or a root cellar (also called earth cellar).

Chilling injury can occur when the watermelon fruit is stored at temperatures below 50°F

Once the fruit has been cut, it will last up to five days in an airtight container if refrigerated.

Watermelon Preservation

There are a number of ways to preserve watermelon; beyond keeping them in their natural undisturbed state in cool rooms. All these methods, as with most other fruits, require the watermelons to be physically altered in one way or the other. These are some of the ways to preserve the melon fruits longer:

Drying

Dehydration is a method employed in preserving many fruits and can be used to preserve the watermelon fruit as well. The dried fruit is called watermelon jerky. It has a leathery texture. Drying gives it more concentration of sugars and flavors. The watermelon is cut into half an inch thick slices and dried for about 20 hours at 135°F.

Freezing

The watermelon can be frozen and kept for longer periods. The texture of the fruit changes significantly. It can also be quite mushy when it thaws.

Canning

They can be canned in the form of pickles, jam, juice, or wine. Since the fruit is a low acid food, it will need to be pickled if it is to be canned; this can either be done with a hot water bath or a pressure canner (for non-acidic preparations).

Here is a video below showing you how to grow watermelon plants from seeds:

FAQ

What month do you plant watermelon?

The best month to plant watermelon is in June (at the end of spring or the beginning of summer). If you are in the northern hemisphere (if you are in countries such as UK or USA) then plant your melon plants around June, because the soil temperature is above 21 degrees Celsius ( or 70 degrees Fahrenheit) which is the suitable temperature needed for growing watermelons.

How many watermelons do you get per plant?

You get about 2 to 4 watermelon fruits per plant. The fruits are produced from healthy vines. The female flowers are responsible for fruit production in watermelons, unfortunately, the female flowers are less compared to the male flower per watermelon plant. Therefore, having 2 or even 4 watermelons per plant is a good yield.

Do watermelons plant come back every year?

Watermelons do not grow back every year because the plants do not survive during the dry seasons; therefore you need to plant them every year.

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