How To Grow Watermelons

Like tomatoes, watermelons are true berries. They can be easily grown in homes and small gardens, but they require space, good and moist soil, plenty of sun, and often protection from various diseases and pests.

But who doesn't like a slice of cold watermelon during the summer heat ...

how to grow a watermelon

Watermelons are one of the favorite refreshment fruits and snacks for many people. Many people wonder if watermelons are healthy at all and how many calories they contain - for more info regarding this topic, feel free to check Health Benefits of Watermelon article.

Watermelons are native to Africa, and they need warmth, sun, and plenty of nutrients to grow and bear fruits. The size of varieties varies, but generally, they also need lots of space.

Optimum temperatures for watermelons are around 26-28°C (around 80° Fahrenheit). Temperatures below 12°C (54°F) and above 40°C (104°F) will stop plants' growth. Also, watermelons are very sensitive to frost, and such temperatures can kill not only their vines but entire plants.

Watermelons grow best in soils with pH between 6 and 6.5 but will tolerate anything between 5 and 7. Again, they require plenty of nutrients and moisture, but they don't like soggy soils.

Soil Preparation and Fertilization

If you want to grow watermelons in your home garden in late autumn, add (aged) manure, compost, humus, seaweed, and some balanced NPK fertilizer like 15:15:15. Some people are 'afraid' that excess rain will wash away nitrogen from the soil, over winter - however, they are NOT concerned without a good reason! Although autumn fertilization is not an absolute requirement, it is a good thing to do.

Till the soil 30cm (one foot) deep and let it settle down till early spring. Watermelons have shallow roots, and there is really no need to till the soil deeper than 40cm (16 inches).

how to grow watermelonsIn early spring, check pH and, if required, adjust it.

Add again some aged manure and other organic fertilizers and balanced NPK fertilizer - amounts depend on the quality of your soil, used varieties, and density of plants - and dig everything some 15 cm (6 inches) deep.

Some growers tend to "force" nitrogen levels during watermelon growth and then "cut down" on nitrogen when flowering starts in order to promote the growth of fruits. In small gardens, it is perhaps not the easiest thing to do and, after all, IMHO, not necessary.

Good preparation of the soil is very important, and when done properly, all one can do is add some 15:15:15 or some similar NPK fertilizer with emphasis on potassium to the flowering plants. Amounts depend on the plants, but 30g (an ounce) per plant every few weeks is enough.

Depending on the variety, days to maturity range from 70 to 90. That and the fact that some varieties have two or more crops per growing season (or they bear fruits for a couple of weeks - depending on how one sees it) means that soil must be kept fertile and moist all the time.

During the growing season, watermelons require 2.5 - 5 cm (1-2 inches) of water weekly. In order to avoid or at least decrease issues with some diseases, water the soil directly and avoid watering 'from above' - if it must be done, water the plants early in the morning, so that leaves can dry quickly.

If possible, protect the soil using non-transparent foil and use a dripping watering system under the foil. During hot days, some leaves' wilting might occur even if plants are properly watered. If wilting is present in the morning, water even more.

Note: somewhat reduced watering during the last week before harvest can increase the sweetness of the fruits. Also, removing vines is not necessary for this purpose.

How Long Does it Take to Grow a Watermelon?

Growing watermelons, a cherished summertime fruit, involves a process that can vary in duration depending on several key factors. The journey from seed to harvest typically spans between 70 to 90 days, but this timeframe is influenced by the watermelon variety, growing conditions, and whether seeds are started indoors or directly sown in the ground.

Watermelon varieties are numerous, each with its own set of characteristics, including size, color, and, importantly, days to maturity. Early-season varieties can mature in as little as 70 days, while larger, late-season types may require up to 90 days or more to fully develop. It's crucial for growers to select a variety that fits their climate and growing season length, especially in areas with shorter summers.

The growing environment plays a significant role in the development of watermelons. Optimal conditions include warm soil temperatures, at least six to eight hours of daily sunlight, and consistent moisture. Starting seeds indoors can give a head start of about 2 to 3 weeks, particularly in regions with shorter growing seasons. This method requires transplanting seedlings outdoors once the threat of frost has passed and soil temperatures have sufficiently warmed, which can help to maximize the growing season and increase the chances of harvesting ripe watermelons.

Moreover, watermelon vines thrive in well-drained, fertile soil with a pH between 6.0 and 6.8. Regular watering, particularly during fruit set and growth, is essential to prevent stress that could hinder development. Additionally, the use of mulch can help maintain soil moisture and temperature, suppress weeds, and protect the fruit from soil contact, reducing the risk of disease and pests.

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Can Watermelons Be Grafted

Grafting, a horticultural technique used to join parts from two or more plants so they grow as a single plant, has been successfully applied to watermelons, offering a variety of benefits along with certain challenges.

This method involves attaching the scion, or upper part of one plant (in this case, the watermelon), to the rootstock of another plant, usually chosen for its robust root system and resistance to soil-borne diseases and pests. The primary goal of grafting watermelons is to produce a more vigorous, disease-resistant plant capable of yielding higher-quality fruit under less-than-ideal growing conditions.

The most common rootstocks used for grafting watermelons are from the Cucurbitaceae family, which includes squash, pumpkin, and certain types of gourds. These plants are selected for their strong root systems that offer enhanced water and nutrient uptake, as well as resistance to common soil pathogens and pests such as fusarium wilt and root-knot nematodes.

Grafting onto these rootstocks can significantly increase the resilience of watermelon plants, allowing them to thrive in areas where soil-borne diseases might otherwise devastate a crop.

The advantages of grafting watermelons are notable. Grafted plants often exhibit increased vigor and yield, improved water and nutrient efficiency, and enhanced resistance to stressors like salinity and drought. Additionally, they can be a boon for sustainable agriculture by reducing the need for chemical soil fumigants and pesticides, thereby minimizing the environmental impact of watermelon cultivation.

However, there are also disadvantages to consider. The process of grafting watermelons is labor-intensive and requires a high level of skill, which can lead to increased production costs. There is also the risk of graft incompatibility, where the scion and rootstock do not successfully unite, leading to plant loss. Moreover, while grafting can enhance disease resistance, it does not improve tolerance to all diseases, especially those affecting the foliage or fruit directly.

In practice, grafting watermelons involves delicate techniques such as the tongue approach, where a slanting cut is made in both the scion and rootstock, and the two parts are joined together. The graft junction must then be kept in a humid environment to encourage the tissues to fuse properly, a process that requires careful management to prevent disease and ensure high survival rates.

Most Popular Watermelon Varieties

Here are some of the most popular watermelon varieties, along with a brief description of each:

  • Black Diamond: This variety is known for its thick, dark green rind and deep red, sweet flesh. Black Diamond watermelons can grow to be quite large, often weighing up to 50 pounds, making them a favorite for their impressive size and delicious taste.
  • Crimson Sweet: A favorite among gardeners for its disease resistance and sweet flavor, Crimson Sweet watermelons feature a light green rind with dark green stripes. The fruit has bright red, crisp flesh and small seeds, typically weighing 15 to 25 pounds.
  • Early Moonbeam: As the name suggests, Early Moonbeam watermelons mature early, making them ideal for climates with shorter growing seasons. They have yellow flesh with a sweet, honey-like flavor and a light green rind with dark green stripes. The fruits are smaller, around 6 to 10 pounds, perfect for small families.
  • Golden Midget: This variety stands out with its golden-yellow rind and pink-red flesh. Golden Midgets are small, with fruits typically weighing around 3 pounds, making them easy to harvest and store. Their early maturity and unique color make them a popular choice.
  • Jubilee: Jubilee watermelons are known for their oblong shape and bright red, sweet flesh. They have a light green rind with dark green stripes and can weigh between 20 to 40 pounds. Jubilee watermelons are valued for their thirst-quenching properties and are a staple at summer gatherings.
  • Moon and Stars: Named for its distinctive rind that resembles a night sky, with one large yellow "moon" and smaller "stars," Moon and Stars watermelons have dark green rinds and sweet, red flesh. This heirloom variety can vary in size but typically produces large fruits.
  • Sugar Baby: A popular choice for home gardens due to its compact size, Sugar Baby watermelons have a dark green rind and sweet, red flesh. The fruits are round and small, usually weighing 6 to 10 pounds, making them perfect for small spaces.
  • Yellow Doll: Yellow Doll watermelons are small, early maturing fruits with a light green rind and bright yellow flesh. Weighing around 5 to 8 pounds, they offer a sweet, tropical flavor that differs from the traditional red-fleshed varieties.

Each of these watermelon varieties offers its own unique flavors, textures, and growing characteristics, making them popular choices among both gardeners and consumers.

Whether you prefer the classic sweetness of a Crimson Sweet or the unique taste and appearance of a Moon and Stars, there's a watermelon variety to suit every preference.

Sowing and Transplanting of Watermelons

Watermelons can be sown directly into the soil, they can be sown in the pots and then transplanted, or they can even be grafted and, after the healing period, transplanted into the garden.

When sowing seeds in the pots, keep in mind that watermelons grow fast, and they can easily overgrow pots and hence have issues with being transplanted onto the permanent position. Unless you live in a cold region, sow seeds directly into the soil, some 30 cm (one foot) apart, with 1.5 - 2 m (5-7 feet) between rows. Again, it depends on the variety used.

When plants start to grow, remove weak ones by leaving every second or third plant to grow.

Since plants are sensitive to low temperatures, sow or transplant plants at least 2 weeks after your last frost day.

Watermelons tolerate fresh manure relatively well - in order to increase warmth around roots, some gardeners add some relatively fresh, decomposing manure around planned planting positions and cover entire rows with foil. Some people even plant a few watermelon plants on used compost/humus piles - warm, rich, well-drained soil, with plenty of water and sunshine - ideal growing conditions for watermelons :)

Mulching can be very beneficial - it protects soil from direct sunlight and prevents excess moisture loss, it prevents weeds from growing, and if mulch is something like compost or aged animal manures, even better - more nutrients for plants. Remember, watermelons are very hungry plants!

Caring for Watermelon Plants

In order to grow strong and healthy, watermelons must have plenty of sunshine, moisture, nutrients, and space.

Watermelons grow male and female flowers, so it is normal for male flowers to fall off. If female flowers are falling off, insects are not fertilizing them (bad weather, strong winds, etc.), but this can be done easily by hand and with great care - take a soft, small brush and after gently brushing 2-3 male flowers, brush female flower - do this for every female flower you see open, once or twice per day - female flowers rarely stay open longer than a single day.

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Bad weather can hamper natural pollination and reduce watermelon crops significantly.

As fruits are growing, prevent the rotting of the melons by putting them on cardboard or straw. In colder areas, fruits can be positioned on aluminum foil in order to increase the warmth and sun exposure of fruits - this speeds up harvesting a little bit and (allegedly) can increase the sweetness of the watermelons.

Some gardeners even lift watermelons entirely off the ground using mesh fruit bags - this way, watermelons are kept away from the rodents and other pests that could damage the fruit and are safe from rotting.

Slugs are dangerous to small watermelon plants - they can even kill the small plant. Plants can be treated against these pests, but in small gardens, remove them by hand. Watermelon grows rapidly, and a single slug (hard to spot and remove) can't really hurt it.

Soil diseases are prevented by crop rotation and by planting grafted watermelons.

One of the biggest watermelon pests are the leaf and flower-eating bugs like spotted and striped cucumber beetles, pumpkin beetles, and other similar pests. They can be treated chemically, just be sure to read the manual carefully.

Since watermelons grow fast enough, they can cope with few bugs, especially in a healthy garden where crop rotation and diversity of plants is the norm!

If the leaves are kept dry, there should be no issues with mildew and similar fungus (leaves look like they are covered with some white powder). If they occur, treat them chemically (sorry to say that again), just be sure to read and understand the manual - some of the chemicals will end up on the fruits, and nobody wants freshly treated food on the table!

Harvesting and Storage of Watermelons

Only when you cut the watermelon and try it yourself will you know if the watermelon is ripe or not :)

ripe watermelon

The easiest method is thumbing on the fruit and listening to the sound. If watermelon sounds like it is:

  • full - watermelon is not fully ripe;
  • half full - watermelon is perfectly ripe;
  • empty - you are too late, it's overripe.

Also, when a watermelon is still green, it has a white bottom, while a ripe watermelon has a yellowish-colored bottom.

Be sure to check tendril:

  • if it's green, the watermelon is not ripe;
  • if it's half-dead, the watermelon is nearly ripe, or ripe;
  • if the tendril is dead, the watermelon is ripe or overripe.

One of the methods is squeezing the fruits between hands - ripe watermelons give a little bit. This also can damage the fruits, so be gentle.

Obviously, there are many ways to check if watermelons are ripe or not. It is an art - eventually, you will have to pick a melon and try it.

When picked, watermelons can be stored in a dry, cold, and dark room or basement for several weeks.

If you live in a warmer area, plant watermelon plants every few weeks to prolong the harvesting season.

Good luck! :)

For more information about watermelons, feel free to check the following:

or check the following watermelon articles:

Guide to Watermelon Companion Plants

watermelons mGrowing plants alongside each other in many different combinations can have plenty of benefits! If the plant you’re growing is a watermelon, you may be looking for a guide to watermelon companion plants.

Watermelon plants need sandy, loose soil with pH levels between 6.0 and 6.8, 8 hours of full sunlight, and a temperature of 65-95 degrees to produce excellent fruit. With these needs in mind, plants like marigolds, nasturtiums, and radishes make suitable companion plants for watermelons.

Updated: August 28, 2023.

How To Pick A Fully Ripe Watermelon

watermelon in the garden mPicking a fully ripe watermelon can be a bit of a challenge, but there are a few common methods that can help you identify one, regardless if you are buying a watermelon on the market, grocery shop, or you are testing watermelons in your own garden.

Of course, there is no full-proof method for testing how ripe watermelon is, except one - take a sharp knife and slice it open.

Published: April 28, 2023.

How to Grow Watermelons in Containers, Flower Pots, and Grow Bags | The Complete Guide

watermelon w150pxWatermelons can be grown successfully in containers, flower pots, and grow bags if they are provided with the key elements they require: warmth, plenty of sunshine, nutrients, and moist but well-aerated soil.

Watermelons have shallow roots and can be grown in relatively small containers, pots, and grow bags, but they grow vigorously, requiring a constant supply of nutrients and water.

Updated: March 4, 2023.

How to Cut and Serve a Watermelon

how-to-cut-a-watermelon-mWatermelons can be cut in many ways, but most often the simplest way is the best. For me, that means removing both ends of the fruit and then cutting watermelon in slices.

Watermelon can be served in slices or in smaller chunks.

Published: November 30, 2022.

Health Benefits of Watermelon - How Many Calories are in Watermelon?

health-benefits-of-watermelon-1mWatermelons are one of the favorite refreshment fruits and snacks for many people.

However, many people wonder are watermelons healthy at all and how many calories they contain.

Updated: September 19, 2020.