Planting watermelons: expert tips for cultivation

No other fruit is more refreshing on a hot summer day than a watermelon. Here are our best tips for planting watermelons in your own garden.

Watermelons (Citrullus lanatus) are exotic fruits that are mostly imported to our local supermarkets from distant countries. In fact, the green-skinned and pink-fleshed fruit is native to West Africa. Therefore, the delicious fruits grow and feel the best in warm temperatures. Despite watermelon’s climate preferences, with the right tips and tricks it is possible to cultivate it in milder latitudes. This is an overview of how to grow watermelons in the home garden.

Planting watermelons: when, where and how

Although watermelons belong to the gourd family (Cucurbitaceae) together with pumpkins, cucumbers and courgettes, the watermelon is more sensitive to cold than its relatives. For this reason, it is important to choose the right location and time to plant watermelons.

Where to plant watermelons

Watermelon plants have specific soil requirements. The following is essential: watermelons prefer a sandy and humus soil. Soils that are too heavy hinder root penetration and tend to accumulate water. We also recommend preparing the garden bed with a lot of compost before planting so that the watermelon plant gets enough nutrients. In addition to the right soil, a warm, sunny and wind-protected place is ideal to grow melons. The perfect location for example would be by a south wall of the house or in a greenhouse.

Tips for the right location:

• Light and humus soil (heavy soils are not suitable)
• Warm, sunny and wind-protected place
• Optimally in a greenhouse or by a south wall

When to plant watermelons

Watermelons are plants that require warmth – planting watermelons outside too early can therefore be fatal for the vulnerable plants! It is best to plant young melon plants outdoors earliest at the end of May. In a greenhouse you can start as early as April. Temperatures below 12 °C can damage development of a watermelon plant.

How to plant watermelons

The actual planting out of the exotic is rather simple: place the young plants at the right distance in a garden bed. Always calculate 1 to 2 square metres per plant so that it has enough space to grow.

Planting watermelons in a pot

A good alternative to growing melons in the bed is planting them out in a pot. That way, you save space in the bed and still don’t have to do without the delicious fruit. When growing watermelons in a pot, be aware that the soil warms up faster than in the open, but it also dries out quicker. Therefore, choose a pot as large as possible and water it frequently. It is best not to place the plant in the blazing sun, as the soil dries out more quickly there and the risk of damage by drought increases.

Growing watermelons: buying or propagating them yourself?

Before you start growing watermelons in spring, the question arises whether to buy a watermelon plant or propagate it at home from seeds? Here, both options are discussed and we explain advantages and disadvantages of each method.

Propagating watermelons at home

Propagating one’s own watermelon plants is quite unproblematic as germination rate is high. From March to April, insert one seed per growing pot at a depth of about 1 to 2 cm. A temperature of over 18 °C is necessary for germination, ideally 22 to 24 °C. A windowsill is a very good place for cultivation and the first seedlings can be seen after 5 to 10 days. As soon as the first leaves appear, the young plants can be rehomed into larger pots. When repotting, make sure to not damage the roots, as watermelons are very sensitive to injuries.

Instructions for propagating watermelons at home:

• Sowing from March – April at a depth of 1 – 2 cm
• Position on windowsill or in a mini greenhouse (min. 18 °C)
• The first seedlings appear after 5 – 10 days
• Move into larger pots as soon as first leaves appear

Buying watermelon plants

It is of course easier to purchase young watermelon plants in stores. You can buy these in garden centres from May to June and then plant them out in the open. One advantage of these young plants is that they are often grafted on pumpkins and are therefore less susceptible to root diseases. The choice is really up to you and how much money you are willing to pay, because the plants bought in stores in larger quantities are of course considerably more expensive than watermelon seeds.

Watermelon species and varieties

Many people have a certain association when thinking of watermelons: green with a pink flesh. However, watermelons are very diverse. The varieties differ from each other in appearance, but they are all part of Citrullus lanatus which are subdivided into two variations:

1. Citrullus lanatus var. lanatus: Common watermelons cultivated commercially worldwide, belong to this variation. This is the classic watermelon that everyone knows and loves.

2. Citrullus lanatus var. citroides: This wild form of melon grows mainly in Africa and is also known as the tsamma melon. The flesh of this variation is not pink, but yellowish to light green.

The varieties for cultivation in Europe belong mainly to the variation Citrullus lanatus var. lanatus. Some of them can also grow in cooler climates.

These are some of the most popular watermelon varieties; find a more extensive list of watermelon varieties here.

• Bush Sugar Baby
  • New variety derived from the variety Sugar Baby
  • Early ripening with smaller fruits: 2 – 4 kg (1 – 2 fruits per plant)
  • Red flesh with dark skin
  • Plant remains quite compact (1 m² per plant)

• Crimson Sweet
  • Spread worldwide; popular variety
  • Oval and light green fruits; high fruit weight: 5 – 8 kg
  • Aromatic light red fruit flesh
  • Good resistance to leaf rot and other fungal diseases
  • 1,5 – 2 m² per plant

• Red Star
  • Dark skin and deep red flesh; high sugar content
  • Fruit size: 6 – 8 kg
  • The variety is suitable for cultivation in temperate climates and should not be cultivated in rough areas due to the slightly longer ripening period
  • 1,5 m² per plant

Care measures

As soon as the watermelon plant becomes accustomed to its position in the garden, it will accelerate its growth. There are a few instructions to follow to ensure that the plant is sufficiently supplied with water and nutrients.

Watering

Watermelons have a high water requirement – not surprising when you look at the juicy flesh. It is therefore of utmost importance to water the plants sufficiently in summer. The soil should be watered daily, preferably in the mornings, especially during fruit formation. Make sure you only use temperate water, as the plant does not tolerate cold water well. You can use water from the rain barrel for example. When watering, be careful not to wet the leaves as this increases the risk of infection with powdery mildew.

Fertilising watermelons

Watermelons are heavy feeders – a good supply of nutrients is therefore vital. Before planting, work some compost into the bed. In the further course of summer, you should fertilise every two weeks in order to provide sufficient nutrients. Natural fertilisers or organic materials such as horse manure work well.

Harvesting watermelons: how to tell if they are ripe?

The ripening period of watermelons is rather long – the large fruits are only harvested from the end of August into autumn. In order to have the best tasting fruit, it is important to harvest only ripe fruit. Watermelons develop their sweet taste over time as they grow on the mother plant. In order to see whether a watermelon is ripe and ready for harvest, pay attention to these signs:

• Dark green skin with yellowish spots
• Dull sound when you knock on it
• Withering leaves in autumn

Storing watermelons

The shelf life of watermelons is quite limited. Best to consume them quickly. You can store watermelons up to two weeks in room temperature if you leave them uncut. As soon as it is cut, shelf life shortens very quickly and it is advisable to store the fruit in the refrigerator. Freezing watermelons, on the other hand, is not recommended, as the fruit consists mainly of water and consistency worsens after thawing. You can find out more about harvesting and storing watermelons properly here.