Watermelon characteristics, varieties, and cultivation: Complete planting, care, and harvesting guide

Watermelon, scientifically known as Citrullus lanatusWatermelon is one of the world's most beloved fruits, famous for its intensely sweet flavor, refreshing properties, and great versatility in cooking and nutrition. This comprehensive article is the definitive guide to discovering everything about watermelon: its history, botanical characteristics, varieties, nutritional properties, benefits, cultivation techniques, care, pest and disease control, harvesting, storage, and much more.

Origin and evolution of watermelon

Watermelon originates from subtropical and tropical Africa, especially the Kalahari Desert region. Wild varieties have grown there for thousands of years, used since ancient times as a source of hydration by local populations and wildlife due to their abundant water content. Watermelon cultivation gradually expanded to northern Africa and then to Asia and the Mediterranean. Archaeological remains of watermelon seeds have been found in ancient Egyptian tombs, where they were valued for their freshness and hydrating properties.

During the Middle Ages, watermelons arrived in Europe and were later introduced to the Americas by Spanish and Portuguese explorers. In the Americas, watermelons found ideal conditions for cultivation and rapidly diversified. Today, watermelon is grown on all continents. (except Antarctica), being one of the most produced and consumed fruits globally.

Botanical characteristics of watermelon

• Family: Cucurbitaceae. Includes other fruits such as melon, cucumber, and squash.
• Scientific name: Citrullus lanatus (Thunb).
• Plant type: Annual herbaceous plant, creeping or climbing. It can grow up to 4-6 meters.
• Root system: Highly branched, with a deep tap root and shallow secondary roots. Currently, most commercial watermelons are grown grafted onto resistant rootstocks to avoid soil-borne diseases such as fusarium wilt.
• Stems: Cylindrical, herbaceous, covered with silky, shiny hairs. They have tendrils that aid climbing and can reach several meters in length. Secondary and tertiary branches sprout from the axils and can cover large areas.
• Sheets: Petiolate, pinnately split, divided into 3-5 lobes and sublobes, with deep notches. Smooth upper surface and rough underside with very pronounced veins, 6-20 cm long.
• Flowers: Yellow, solitary, axillary, and pedunculated. Watermelon is a monoecious species: it has male and female flowers on the same plant, although in separate flower heads. Pollination is usually done by insects, mainly bees.
• Fruit: It is a peponide (large berry), spherical or ovoid, with a uniform green, striped, or mottled rind. Its weight varies from less than 2 to 20 kilograms or more, depending on the variety. The flesh can be deep red, pink, yellow, or orange.
• Seeds: They vary in size and color (white, brown, black or absent in seedless triploid varieties).

Water contentA ripe watermelon can contain between 90-92% water, making it an exceptionally refreshing fruit.

Varieties and types of watermelon

The world of watermelons is very diverse. They can be classified by size, flesh color, presence or absence of seeds, external shape, and disease resistance. The main categories are:

• Traditional or diploid watermelon: This includes the classic varieties with seeds. They typically weigh between 8 and 15 kg, can be rounded or oval, and have smooth or striped rinds.
• Seedless watermelon (triploid or seedless): Obtained by crossing diploid and tetraploid watermelons. It produces no viable seeds, so the flesh is cleaner and more palatable. They tend to be sweeter and keep better.
• Yellow-fleshed watermelons: As the Yellow Crimson o Golden Yellow, with an external appearance similar to the red ones but yellow or orange inside. They are highly prized for their distinctive, exotic flavor.
• Mini watermelons or small watermelons: Varieties like Sugar Baby, very popular in small homes.
• Square watermelons: A curiosity from Japan and some agricultural experimenters. They are grown in molds for easier storage and transport, although they tend to be more expensive.
• Other classifications: According to the texture of the bark, the quantity or color of seeds, resistance to diseases or early ripening.

Examples of popular commercial varieties

• Crimson Sweet: Striped rind, very sweet red pulp, black seeds.
• Sugar Baby: Small, dark green rind, red flesh, ideal for small spaces or potted crops.
• Yellow Crimson: Yellow pulp, rind similar to Crimson Sweet.
• Black Diamond: Large, smooth rind, dark green, deep red flesh.

Nutritional properties and health benefits

Watermelon is much more than a refreshing fruit. It brings together a set of bioactive compounds, vitamins, minerals and fiber which give it important health benefits.

• High water and fiber content: It provides great hydration and aids digestion.
• Low in calories and fat: Approximately 30-46 kcal per 100 g, making it an ideal food for weight control diets.
• Vitamins: Rich in vitamin A (beta-carotene), vitamin C and B vitamins.
• Minerals: Good source of potassium (essential for water balance and muscle function), magnesium, and small amounts of calcium and phosphorus.
• Antioxidants: Rich in lycopene (hence its red color), an antioxidant that helps protect against cardiovascular disease and some types of cancer, especially prostate cancer.
• Citrulline: An amino acid that promotes blood circulation and can improve cardiovascular function and muscle recovery after exercise.

Main health benefits:

• It promotes hydration during the summer or intense physical activities.
• Rejuvenates the skin thanks to lycopene and other antioxidants, reducing the effect of free radicals.
• Protect the heart for its vasodilatory action and its contribution of compounds that help lower blood pressure.
• Promotes intestinal transit and prevents constipation due to its soluble fiber.
• Helps with weight control being satiating and very low in calories.
• Contributes to kidney and liver detoxification, promoting the elimination of toxins through urine.
• Improves sports performance and post-exercise recovery due to its contribution of citrulline and potassium.
• Anti-inflammatory power, especially due to the lycopene and other phenolic compounds present in the pulp and rind.
• May help with mild erectile dysfunction, since citrulline promotes the relaxation of blood vessels.

How to Grow Watermelon: A Step-by-Step Guide

The success of watermelon cultivation depends on several key factors: the variety chosen, soil preparation, climatic conditions, irrigation, nutrition, and effective pest and disease control. The process is detailed below.

Optimal growing conditions

• Temperature: Watermelon requires warm temperatures. The optimal growth temperature is between 23 and 28°C, although it can tolerate temperatures as high as 32°C during the day. Temperatures below 10-11°C stunt its growth and can cause irreversible damage to young seedlings.
• Light: It requires full sun, with at least 8-10 hours of direct sunlight per day. A shady location reduces fruit production and sweetness.
• Floors: It prefers loose, loamy or sandy-loam soils that are well-drained and rich in organic matter. The ideal pH is between 6,0 and 6,5. Compact or poorly drained soils promote fungal root diseases.
• Humidity: Optimal relative humidity levels between 60-80%, especially during the flowering and fruit setting stages.
• Space: It requires a lot of space so that its stems can expand, avoiding competition for nutrients and light.

Preparation of the land

1. Cleaning and decompacting: Remove stones, weeds, and debris from previous crops. Till the soil to a minimum depth of 30-38 cm to ensure good aeration and root development.
2. Enrichment: Add mature compost, well-rotted manure, or organic fertilizers to improve structure and fertility.
3. pH improvement: If necessary, add agricultural lime to adjust the pH to optimal values.
4. Pre-irrigation: Water the soil and let it warm up before planting.

Planting watermelon

• Direct seed: This is the simplest and most common method. Sow 2-4 seeds per hole at a depth of 2-4 cm, leaving 1,5 to 2,5 m between plants depending on the variety and 1,8-2,4 m between rows.
• Seedbed (indirect sowing): It is grown in trays or containers using a substrate such as coconut fiber, peat, or perlite. It is ideal for cold regions or when harvesting is desired. Seedlings are transplanted to the field when they have 2-3 true leaves and are 5-10 cm tall.
• Graft: Many commercial watermelons are grown by grafting onto hardier rootstocks (usually Cucurbita maxima x Cucurbita moschata) to reduce the risk of soil-borne diseases. Transplanting is done using the root ball to avoid damaging the roots.

Conditions for germination

• Minimum soil temperature: 18°C
• Germination time: Between 7 and 10 days, depending on the variety, temperature and humidity.
• Initial care: Keep the substrate moist (not soaked) until the seedlings emerge. Water preferably in the morning.

Care during development

1. Irrigation: It is essential to keep the soil moist, especially until fruit set. Critical periods are flowering, fruit set, and fruit growth. Irrigation should be frequent but avoid waterlogging. Drip irrigation is recommended for efficiency and better health control.
2. Fertilization: Watermelon is very nutrient-demanding during the fruit development and growth stages. It is recommended to apply all phosphorus and potassium before or during planting, and to divide the nitrogen intake: half at the beginning and the remainder starting 4-6 weeks after planting. Magnesium, calcium, sulfur, and micronutrients (iron, boron, manganese, zinc, copper, and molybdenum) are essential to prevent deficiencies that reduce fruit quality.
3. Indicative dose (for every 40-60T/Ha): N: 150-250 kg/ha; P2O5: 150 kg/ha; K2O: 250-450 kg/ha; MgO: 25-30 kg/ha.
4. Pruning: Although it may not be strictly necessary, pruning helps control growth, focus the plant's energy on the fruit, and improve ventilation. Prune unproductive secondary branches and remove aged or diseased leaves. Fruit thinning is also necessary to leave only the most developed.
5. Padding and microtunnels: The use of plastic mulch helps raise soil temperature, conserve moisture, reduce weeds, and keep fruit clean. Plastic microtunnels are used in early plantings to provide thermal protection. Black mulch reduces weeds, while transparent mulch increases substrate temperature, although it can encourage weed growth.
6. Pollination: Watermelon depends on insect pollination, primarily bees. For triploid watermelons, closely related diploid varieties are planted as pollinators. If pollination is insufficient, the fruit will be deformed and unproductive.

Watermelon watering

• Critical stages: Keep the soil moist from planting until the first fruit sets. During fattening and ripening, gradually reduce watering to concentrate the sugars and prevent fruit cracking.
• Frequency: At first, water briefly and frequently; before and during flowering, water daily; during fattening, water long and at intervals; as the plants mature, reduce the volume and frequency.
• Irrigation methods: Drip irrigation is recommended, which delivers water directly to the root zone and reduces fungal diseases and weed growth.
• Avoid sprinkler irrigation especially during flowering, as it can promote diseases and reduce pollinating activity.

Fertilizing and fertilizing watermelon

• Main fertilizers: Nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur. The contribution must be balanced and adapted to the soil analysis and variety requirements.
• Recommended organic fertilizers: Well-rotted manure, compost, worm castings, as well as seaweed or natural mineral fertilizers.
• Biostimulants: The use of naturally occurring amino acids and biostimulants promotes crop vigor, fruit growth and ripening, and improves stress resistance and nutrient absorption.
• Importance of microelements: Micronutrient deficiencies can manifest themselves in small, deformed or poor quality fruits (poor setting, lack of sweetness, poor coloration, tissue necrosis).

Pruning, vegetation management and thinning

• Pruning main branches: The main shoot can be topped when it has 5-6 leaves to encourage the development of secondary branches.
• Pruning secondary branches: These branches are then topped to limit growth and promote the development of productive shoots.
• Leaf pruning: Remove old, diseased leaves or those that hinder ventilation and light entry.
• Pruning defective fruit: Remove deformed or poorly pollinated fruit and leave one or two fruits per branch, depending on the vigor of the plant.
• Tools: Always use clean and disinfected scissors to prevent the transmission of diseases.

Common diseases and pests in watermelon

Common pests

• Red spider (Tetranychus urticae): Causes yellow spots, weakening, and defoliation. Mechanical and biological control with predatory mites and specific products.
• Aphid: It sucks sap and transmits viruses. It is controlled using color traps, biological control, and specific phytosanitary products.
• Thrips: Causes necrosis and deformations. Reduces quality and production.
• White fly: It sucks sap, weakens the plant and transmits viruses, which are especially dangerous in greenhouses.
• Caterpillars and miners: species like spodoptera, Heliothis, Autographa y Liriomyza They attack leaves and fruits.
• Nematodes: Especially Meloidogyne, which causes nodules in roots, weakening the plant.

More common diseases

• Powdery mildew or ash: Produced by Sphaerotheca and other fungi, white spots on leaves, defoliation and reduced yield.
• Fusarium disease: Fusarium oxysporum f.sp. level, causes wilting, yellowing, and death of plants. Grafting onto resistant rootstocks is the most effective solution.
• Stem rot: Fungal infection that causes stem lesions, gummy discharge, and plant death.
• Viral diseases: Viruses transmitted by insect vectors deform leaves and stunt growth. Insect prevention and control are crucial.
• Mildew, anthracnose, bacteriosis and rot: Various fungi and bacteria cause spots, defoliation and fruit rot.

Integrated control: Constant monitoring and the use of preventative methods such as crop rotation, removal of plant debris, application of approved products, and the use of resistant varieties and grafts are recommended.

Frequent physiopathies

• Fruit cracking: Due to excessive irrigation or sudden changes in soil moisture, especially during ripening.
• Abortion of fruits: Due to poor setting, lack of pollination or environmental stress.
• Root asphyxia: For waterlogged and poorly drained soils.

Harvesting and storing watermelon

The ideal time to harvest watermelon is when the fruit reaches its physiological ripeness.The main indicators are:

• The contact stain with the ground turns yellow or ivory.
• The tendril closest to the fruit is dry and brown.
• The color of the bark changes from shiny to matte.
• The crust becomes hard and difficult to scratch with a fingernail.
• When hitting the fruit, a dull, hollow sound is heard.

Watermelons are cut by hand, leaving part of the stem attached. Avoid bumps and bruises to prevent rot.

Post-harvest storage

• Optimum temperature: Between 10 and 16°C, ideally 13°C.
• RH: 85-90%.
• Avoid temperatures below 10°C: They can cause chilling damage, pulp necrosis, dark spots, and juice leakage.
• careful handling: Transport and store on padded surfaces (hay, straw, soft cloth) to prevent physical damage.
• Separate from fruits that emit ethylene (apples, bananas, pears) to prolong shelf life.
• Maximum duration under optimal conditions: 2 to 3 weeks.

Frequently Asked Questions About Growing Watermelon

How long does it take for a watermelon to grow?

The complete growing cycle depends on the variety, but the period from planting to harvest is typically between 70 and 100 days. Small-fruited varieties can ripen in about 70 days, while large varieties take 90 days or longer.

How many watermelons can one plant produce?

The most common way to obtain watermelons is by planting two or three plants if the plant is well nourished and the fruit is thinned out properly.

What is the recommended distance between plants and rows?

The distance between plants depends on the variety and the cultivation method. Typically, plants should be spaced 1,5 m to 2,5 m apart, with rows spaced 1,8 m to 2,4 m apart. For smaller fruit, the spacing can be reduced.

What causes watermelon to crack?

Cracking is usually caused by sudden changes in humidity, overwatering during the ripening stage, or rapid growth due to sudden availability of water and nutrients.

How can you get seedless watermelon?

Seedless watermelons are obtained by crossing a diploid plant (normal number of chromosomes) with a tetraploid plant (four sets of chromosomes), generating triploid plants whose fruits do not develop viable seeds.

What are the best practices for watermelon in an organic garden?

Use resistant varieties, rotate crops, enrich the soil with organic matter, and control pests and diseases using biological and preventative methods.

Curiosities and alternative uses of watermelon

• In the kitchen: In addition to being eaten fresh, watermelon is a staple in salads, juices, ice cream, desserts, and even stews, especially in Asian and Mediterranean cuisine.
• Medical uses: In traditional African and Asian medicine, watermelon has been used to treat urinary and digestive problems.
• Ornamental watermelon: There are ornamental varieties with curious shapes and colors that are used in decoration.
• square watermelon: Grown in molds for easy transport and storage.

When choosing the most suitable watermelon variety and cultivation method, it is important to understand not only the plant's needs but also the possibilities for improvement and adaptation to the conditions of each soil. Watermelon can be a great ally in both family gardens and intensive commercial farms and greenhouses, thanks to its genetic diversity, agroecological adaptation, and the possibility of innovative grafting techniques and integrated management. Following these tips will allow you to achieve a bountiful harvest of large, juicy, and high-quality fruit, while also contributing to agricultural and culinary sustainability.