Benjis Seeds

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<tc>Watermelon planting – professional guide for successful cultivation</tc>

Until today, watermelons delight people with their diversity and flavour. On hot summer days they offer natural refreshment – and with our tips and tricks, cultivation succeeds both in the subtropical south and in temperate central Europe.
Wassermelonen pflanzen – Professioneller Leitfaden für den erfolgreichen Anbau
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This cultivation guide explains how traditional, open‑pollinated varieties thrive reliably under different climate conditions and which factors are essential for a successful growing season.

Table of contents

1. Herkunft und Klima der Wassermelone 
  • Anbau im subtropischen Klima
  • Anbau im gemäßigten Klima
2. Standortwahl für den erfolgreichen Wassermelonen-Anbau 
  • Die vier wichtigsten Standortfaktoren
  • Warum die Faktoren wichtig sind
  • Standort im subtropischen Klima
  • Standort im gemäßigten Klima
  • Zeitpunkt im subtropischen Klima
  • Zeitpunkt im gemäßigten Klima
  • Wassermelonen im Freiland
  • Wassermelonen im Topf
  • Wassermelonen Setzlinge kaufen
  • Bewährte samenfeste Sorten
  • Seltene Sorten aus Heirloom‑Archiven
6. Pflege für Wassermelonen im Überblick 
  • Gießen
  • Düngen
  • Triebe schneiden
  • Spezielle Klima-Pflegehinweise für Wassermelonen
10. Fazit

Origin and climate of the watermelon

Watermelons belong botanically to the gourd family (Cucurbitaceae), yet their heat requirement is significantly higher than that of cucumbers or classic pumpkin varieties. Watermelons (Citrullus lanatus) originate from the hot regions of West Africa, where temperatures above 40 °C, dry air and intense sunlight are part of everyday life. This origin explains their high need for warmth and their ability to grow vigorously and develop aromatic fruits under intense heat.

Cultivation in subtropical climates

In subtropical regions such as southern Portugal, southern Spain, Greece or Turkey, summer temperatures regularly rise above 35 °C. The air is dry, nights remain warm and the sun stands high. Under these conditions watermelons grow particularly reliably. They continue flowering even in intense heat, as long as water supply remains stable and air can circulate well. The dry air reduces the risk of fungal diseases, while the strong sunlight produces sweet, aromatic fruits.
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‘Crimson Sweet’, a proven large watermelon variety

Cultivation in temperate climates

In temperate regions such as Germany, Austria, Switzerland or southern England, summers are warm but less extreme. Humidity is higher, and mornings are often moist. Watermelons grow well here too, but they require a very sunny and warm location, good air circulation, consistent watering and varieties with a shorter ripening period. Warmth remains the most important factor, yet air movement and moisture management are equally essential.

Location selection for successful watermelon cultivation

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A partially sheltered location provides protection and air circulation
An optimal location reflects the natural conditions of the watermelon: plenty of sun, warm soils, dry air and well‑drained, nutrient‑rich earth. Melons are sensitive to unsuitable locations, so it is worthwhile to consider the key factors carefully.

The four most important location factors

  • Deep, well‑drained, sandy‑humus loam
  • Incorporation of compost as a nutrient base
  • Warm, sunny and slightly wind‑sheltered location
  • Mulch layer for temperature and moisture regulation

Why the factors matter

Heavy soils hinder root penetration and tend to cause waterlogging. Loosening the soil to around 40 cm depth creates ideal conditions for root development. Compost provides the necessary nutrients, and a sunny location with up to eight hours of sunlight ensures even ripening. A slightly wind‑sheltered spot retains warmth, while moderate airflow dries the plants quickly and helps prevent fungal diseases. A mulch layer stabilises soil temperature, retains moisture and protects against erosion.

Location in subtropical climates

Hot, dry summers provide ideal conditions for late‑ripening varieties. Under these circumstances, the plants develop vigorously and set fruit reliably. Good air circulation is important, especially at temperatures above 35 °C.

Location in temperate climates

Early varieties are particularly suitable here. A bed against a south‑facing wall, a raised bed or a polytunnel provides additional warmth – especially at night, when temperatures should remain above 12 °C. This makes it possible to create stable growing conditions even in cooler regions.

The right time to plant watermelons

Watermelons are sensitive to cold. Planting them out too early leads to growth stagnation and stress, while planting too late shortens the ripening period. Choosing the right moment is therefore a key factor for success.

Timing in subtropical climates

  • Pre‑cultivation from mid‑February
  • Direct sowing from late March
  • Planting out from early April to June

Timing in temperate climates

  • Pre‑cultivation from April
  • Greenhouse planting from late April
  • Planting out in open ground from late May to early June
benjis-seeds-citrullus-lanatus-watermelon-sugar-baby-young-plant-blog
Mulch promotes watermelon growth during heat

Watermelons in open ground

Cultivation varies by climate, but in both open ground and greenhouse conditions watermelons achieve the best growth when provided with sufficient warmth and space. Each plant needs ample room: for healthy development, around 1–2 m² per watermelon should be planned. The plants grow quickly, form long vines and require enough space to produce strong, well‑formed fruits. A sunny, well‑warmed location further supports growth and ensures that the fruits develop their full flavour.

Watermelons in pots

If you do not have a garden, growing watermelons in large containers is also possible. For container cultivation, very large pots are necessary – around 50 litres in volume, so that the roots can develop well. The soil warms up more quickly in a pot but dries out just as fast. Regular watering is therefore especially important. A layer of mulch helps to retain moisture and stabilise soil temperature, allowing the plants to grow reliably even in pots. Additionally, the container can be shaded with suitable materials to prevent the soil from overheating.

Watermelon plants – sow yourself or buy seedlings?

Watermelons can be easily started indoors thanks to their high germination rate. Because of their sensitive roots, they should not be pricked out; one seed per pot is ideal. Germination succeeds reliably at warm temperatures and consistent moisture. Both methods produce strong plants; the choice depends on whether you prefer to save time or accompany the entire growth process yourself.
  • Sowing depth: 1–2 cm
  • Germination temperature: 22–30 °C
  • Germination time: 6–12 days

Buying watermelon seedlings

A time‑saving option is to buy already pre‑grown young plants. They are available from April to June directly from Benjis Seeds in Portugal or from many regional nurseries. Pre‑grown plants make it easier to get started and significantly shorten the overall cultivation period.

Watermelon variety diversity – traditional, open‑pollinated classics

Many associate the watermelon with the classic large green fruit and its intensely red flesh. In reality, the species Citrullus lanatus encompasses a remarkable and mostly unfamiliar diversity. The different varieties vary significantly in colour, patterning, size and flesh characteristics, yet all belong to the same botanical species.
Three variations are distinguished:

Citrullus lanatus var. lanatus

This variation includes the cultivated watermelons, meaning all familiar garden and commercial varieties. These comprise classic, historical and modern types with green, yellow, striped or mottled rinds, as well as red, pink, yellow or orange flesh. It represents the full range of sweet, fresh‑eating cultivated forms and is distributed worldwide.
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Watermelon variety diversity: ‘Orangeglo’

Citrullus lanatus var. citroides

This variation includes the traditional preserving and fodder melons, which also encompass the classic jam melons. They have very firm, white to pale green flesh, are not very sweet and possess an extremely thick rind. Thanks to their long storage life and robust structure, they are ideal for boiling down, candying and other forms of processing. Historically, they were used both in the kitchen and as animal feed.

Citrullus amarus

The Tsamma melon is an African wild form and, contrary to commonly spread assumptions, does not belong to C. lanatus var. citroides. It has bitter or bland flesh, is highly drought‑resistant and is considered an original wild form that plays an important role in the genetic foundation of today’s cultivated melons. It is not suitable for consumption.

Proven open‑pollinated varieties

Sugar Baby – known since 1955

  • Rind: dark green, smooth
  • Flesh: deep red
  • Size: small to medium, compact
  • Maturity: very early (approx. 2 months)
  • Climate: perfect for temperate and warm regions
  • Flavour: intensely aromatic sweet, dense, full‑bodied
  • Special features: ideal for small gardens and short summers

Crimson Sweet – known since 1964

  • Rind: classic green, lightly striped
  • Flesh: red
  • Size: medium‑sized
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm to hot regions
  • Flavour: classic sweet, balanced, refreshing
  • Special features: very robust, reliable, versatile

Golden Midget – known since 1959

  • Rind: bright yellow
  • Flesh: pink‑red
  • Size: small
  • Maturity: very early (approx. 2 months)
  • Climate: suitable for cool or changeable summers
  • Flavour: mildly sweet, pleasantly light
  • Special features: turns fully yellow when ripe → easy to recognise

Moon and Stars – known since the 1920s

  • Rind: dark green with yellow speckles
  • Flesh: red
  • Size: medium to large
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm to hot regions
  • Flavour: aromatic, robust, classic heirloom character
  • Special features: historic landrace with a unique pattern

Orangeglo – known since the 1960s

  • Rind: light green, striped
  • Flesh: orange
  • Size: large
  • Maturity: mid to late (approx. 3.5–4 months)
  • Climate: ideal for hot regions
  • Flavour: very sweet, fruity, slightly tropical
  • Special features: intense aroma, striking colour

Cream of Saskatchewan – known since the early 20th century

  • Rind: light green, lightly striped
  • Flesh: white‑yellow
  • Size: small to medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: suitable for cool to temperate regions
  • Flavour: exceptionally sweet, creamy, delicate
  • Special features: historic landrace from Russia/Canada
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Citrullus lanatus var. citroides Jam Melon

Rare heirloom varieties from archival sources

Yellow Crimson – known since the 1960s

  • Rind: green striped
  • Flesh: yellow
  • Size: medium to large
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: sweet, mildly fruity, very pleasant
  • Special features: classic yellow‑fleshed heirloom variety

Desert King – known since the mid‑20th century

  • Rind: light green, solid
  • Flesh: yellow
  • Size: large
  • Maturity: mid‑season (approx. 3 months)
  • Climate: highly drought‑resistant, ideal for hot and arid regions
  • Flavour: mildly sweet, soft, refreshing
  • Special features: extremely robust traditional US variety

Mountain Sweet Yellow – known since the 19th century

  • Rind: dark green striped
  • Flesh: yellow‑orange
  • Size: large
  • Maturity: mid to late season (approx. 3.5–4 months)
  • Climate: ideal for warm regions
  • Flavour: very sweet, bold, full‑bodied
  • Special features: old US landrace with a strong aroma

Yellow Petite – known since the mid‑20th century

  • Rind: dark green, lightly striped
  • Flesh: yellow
  • Size: small
  • Maturity: very early (approx. 2 months)
  • Climate: suitable for short summers
  • Flavour: aromatic‑sweet, light and fresh
  • Special features: compact traditional variety

Tendersweet Orange – known since the early 20th century

  • Rind: light green striped
  • Flesh: pale orange
  • Size: medium to large
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: very sweet, soft, delicately fruity
  • Special features: historical variety with a very tender texture

Orange Tendersweet – known since the 1930s

  • Rind: light green striped
  • Flesh: orange
  • Size: medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: warm to hot
  • Flavour: sweet, aromatic, slightly spicy‑fruity
  • Special features: traditional historical US variety, very sweet

Golden Honey – known since the 1940s

  • Rind: light green striped
  • Flesh: intense yellow
  • Size: medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: very sweet, honey‑like, intense
  • Special features: strong sweetness, rare heirloom variety

Apricot Watermelon – known since the early 20th century

  • Rind: green striped
  • Flesh: apricot‑coloured
  • Size: medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: sweet, apricot‑like, slightly floral
  • Special features: rare apricot‑coloured historical landrace variety

Golden Sweet Orange – known since the 1950s

  • Rind: light green striped
  • Flesh: orange‑apricot
  • Size: medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: sweet, fruity, slightly tropical
  • Special features: striking colour, rare variety

Peach Watermelon – known since the early 20th century

  • Rind: green striped
  • Flesh: pale orange
  • Size: medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: mildly sweet, soft, peach‑like
  • Special features: peach‑coloured texture, historical variety

White Wonder – known since the 1940s

  • Rind: light green, lightly striped
  • Flesh: pure white
  • Size: medium
  • Maturity: mid‑season (approx. 3 months)
  • Climate: warm to temperate
  • Flavour: mildly sweet, very tender, slightly floral
  • Special features: rare white heirloom melon

White Seeded Watermelon – known since the early 20th century

  • Rind: green striped
  • Flesh: white
  • Size: medium to large
  • Maturity: mid‑season (approx. 3 months)
  • Climate: ideal for warm regions
  • Flavour: mild, slightly sweet, very refreshing
  • Special features: white seeds, rare historical line

Care for watermelons at a glance

Watering

Watermelons have a high water requirement. During fruit development they should be watered daily in the evening so the water can penetrate deeply into the soil. The plants do not tolerate cold water well, so collected rainwater or water from storage containers is particularly suitable. Even moisture ensures that the fruits grow evenly and develop an intense aroma.

Fertilising

Watermelons are heavy feeders and need a good nutrient supply. Compost is the ideal base. A fertilisation 4–6 weeks after planting supports fruit development. Watermelons are sensitive to excess nitrogen; a balanced, potassium‑rich supply enhances colour and sweetness. Organic fertilisers are particularly suitable because they release nutrients slowly and provide the plant with an even supply.

Pruning shoots

Watermelons grow quickly and produce long vines that consume a lot of energy. Targeted pruning ensures that the plant does not channel its strength into excessive leaf and vine growth but instead into developing its fruits. Pruning keeps the plant tidy, improves air circulation and helps the fruits gain size and aroma. This creates balanced growth, with a stable plant that produces high‑quality melons. Regularly training the vines also improves air flow and prevents the fruits from resting on damp soil.
The important thing is not to prune too heavily: The plant thrives best when it retains enough leaf mass for photosynthesis and can focus on strong, well‑developed shoots.
  • Main shoot let grow: The strongest shoot remains untouched and carries the main fruits.
  • Shorten side shoots: Shorten side shoots after the 1st–2nd fruit set so that the plant distributes its energy in a targeted way.
  • Limit number of fruits: Leave 3–4 fruits per plant and remove surplus fruits early.
  • Remove weak or damaged shoots: Everything that is thin, diseased or poorly developed is cut off.
  • Raise or shorten vines lying on the ground slightly: This prevents moisture and rot and ensures that the fruits dry better and receive more light.

Special climate care instructions for watermelons

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During the longer season, plants grow more vigorously. Regularly shorten the side shoots and check the stand more often. Also keep the soil moisture stable, as periods of heat increase water demand. In very hot regions, the plants benefit from lightly mulched soil to retain moisture for longer. On warm nights the plants grow particularly strongly, so an occasional check of the vine training is worthwhile to keep the watermelon plants tidy.

Care in temperate climates

Reduced growth and a shorter season. Limit the fruits early so the plant can focus its energy on a few melons. Also ensure good soil warmth, as cooler soils slow growth. In cooler regions, a sheltered location helps to keep soil temperatures stable. In areas with changeable weather, a light mulch layer supports soil warmth and keeps moisture more even.
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With a bit of care, cultivation also succeeds in temperate climates

Reliable recognition of watermelon ripeness signs

Watermelons show several ripeness signs at the same time, and only the interplay of these characteristics makes a reliable assessment possible. Individual indications can be misleading depending on variety, climate or location – therefore never rely on just one sign. When several of the following points occur simultaneously, the watermelon is reliably ripe.
Watermelons usually ripen from June in subtropical climates, and from late August into autumn in temperate climates. The following compact characteristics will reliably help you everywhere.
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Dry tendrils are a clear sign of ripeness in hot climates
  • Yellow ground spot – the resting point is a strong yellow rather than whitish.
  • Dull sound – deep and full when tapped.
  • Matte rind – less shine, slightly dull surface.
  • Heavy weight – feels heavier than it looks.
  • Light sweet scent in high heat
  • Tendrils dry earlier (subtropical climate)
  • Tendril growth slows down (temperate climate)

Common problems and solutions in watermelon cultivation

The cultivation of watermelons is usually reliable, yet typical problems occur now and then in both temperate and subtropical climates. Cold stress, waterlogging, nutrient deficiencies, weak pollination or extreme heat can noticeably affect growth, fruit set and flavour. This section summarises the most common problems in watermelon cultivation and offers practical, directly applicable solutions to help the plants grow steadily, stay healthy and develop aromatic fruits.

Low growth, few flowers and limited fruit set

Cold stress: nights below 12 °C slow down growth, flowering and fruit set
→ Solution: Protect plants (mulch, fleece, small tunnel), choose warmer spots, plant out later

Root rot and growth stop

Waterlogging: Excessively wet soil leads to root rot and a complete halt in growth.
→ Solution: Loosen the soil, improve drainage, reduce mulch, water less, slightly raise the bed (mound bed) so that water drains away more quickly.

Few fruits

Overfertilisation with nitrogen: The plant produces a lot of leaf mass but very few fruits.
→ Solution: Limit the number of fruits: leave 3–4 fruits per plant and remove excess vines and fruits early, reduce fertilisation, switch to balanced or potassium‑focused fertilisers, work in biochar on the surface, use compost instead of synthetic fertiliser.

Small fruits or dropping fruit sets

Too many fruits per plant: The energy is spread out, fruits stay small or drop off.
→ Solution: Limit the number of fruits early (depending on the variety, 3–4 per plant), remove weak fruits.

Pale and moderately developed flesh

Poor pollination: Few insects lead to pale, poorly developed fruits.
→ Solution: Ensure insect‑friendly conditions, gently shake the vines in the morning.

Weak and small plants

Compacted soil: Roots cannot grow deep, the plant remains weak and small.
→ Solution: Loosen the soil deeply (at least 40 cm), work in sand, expanded clay (Sterolith), biochar, rock dust or compost.

Fungal diseases

Air stagnation: Humid, still air favours fungal diseases and stops flowering.
→ Solution: Improve air circulation, avoid planting too densely, lift, reposition or shorten the vines.

Small and low‑aroma fruits

Too little sun: Fewer than 6–8 hours of sunlight per day result in small, low‑aroma fruits.
→ Solution: Choose a full‑sun location, avoid placing shade‑casting plants nearby or prune them.

Cracks, small fruits or watery flavour

Irregular watering: Leads to cracks, small fruits or watery flavour.
→ Solution: Water evenly, irrigate in the morning or evening, use mulch, work in biochar or expanded clay (Sterolith).

Low colour development

Heat stress: Above 40 °C stops colour formation and produces pale flesh.
→ Solution: Provide light shading on extremely hot days, water the soil lightly in the morning to benefit from evaporative cooling, keep soil moisture stable.

All important factors for growing watermelons at a glance

  • Full sun
  • Warm soil
  • Even watering
  • Air circulation
  • Balanced nutrients
  • Limit number of fruits
  • Observe signs of ripeness

Quote

Watermelons are impressive cultivated plants with a long history and great adaptability. With traditional, open‑pollinated varieties, a suitable location and a bit of background knowledge, cultivation succeeds both in the subtropical south and in temperate Central Europe. Anyone who takes the key factors into account will be rewarded with aromatic, high‑quality fruits.
Seeds for open‑pollinated varieties order online

'Sugar Baby' Watermelon - Citrullus lanatus

  • Early, compact watermelon
  • Open‑pollinated, proven traditional variety
  • Ideal for temperate and subtropical climates
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