Melons

Start from seed: October-November

Optimum soil temperature for germination: 22-27°C

Plant seedlings: November

Plant spacing: 60-100 cm

Days to maturity: 80-140 days

Introduction

Melons (Cucumis melo for rockmelon and honeydew, and Citrullus lanatus for watermelon) are members of the Cucurbitaceae family, which also includes cucumbers, pumpkins, and zucchini. These trailing vines produce some of summer’s most refreshing fruits and are a rewarding crop for home gardeners with sufficient space.

Watermelons are believed to have originated in Central Africa, while rockmelons and honeydew melons have their origins in tropical west Africa and were introduced to Europe 2000 years ago Melons have been cultivated for thousands of years, with evidence of watermelon cultivation dating back to the middle east, Russia, China and ancient Egypt, where they were even placed in the tombs of pharaohs as food for the afterlife. A distinct group of melons, known as Cantaloupes, were developed in Cantallouppi near Rome.

In Australia, the three main types of melons grown are watermelons with their characteristic red or pink flesh and green rind, rockmelons (also known as cantaloupes) with orange flesh and netted skin, and honeydew melons with pale green flesh and smooth, cream to yellow skin. Each offers a distinct flavour profile, from the juicy sweetness of watermelons to the aromatic richness of rockmelons and the more subtle sweetness of honeydew melons.

Site and soil

Melons can be grown successfully in Canberra, though they require a warm growing season with plenty of sunshine. Choose a protected site that receives at least 6-8 hours of full sun daily. It helps to choose varieties suited to our relatively short growing season.

Prepare the soil thoroughly before planting by incorporating plenty of well-rotted compost or aged manure and a complete organic fertiliser. Melons prefer fertile, well-draining soil with a pH between 6.0 and 7.0. Creating raised mounds about 15-20 cm high can improve drainage and help the soil warm faster, which is particularly important in Canberra’s climate.

For container growing, choose very large containers (at least 50 litres in volume) with good drainage holes. Use a high-quality potting mix enriched with compost and complete organic fertiliser. Note that container-grown melons will need more frequent watering and may produce smaller fruits than those grown in the ground.

For details on preparing soil and pots, including the use of lime, dolomite, gypsum and fertilizers, please refer to the COGS guide to garden bed preparation.

Planting Seeds and Seedlings

In Canberra, melons should be planted after all danger of frost has passed and when soil temperatures have warmed to at least 18°C. Direct sowing is often more successful than transplanting, as melons don’t appreciate having their roots disturbed.

For direct sowing, plant 3-4 seeds in groups, 2-3 cm deep, spaced 60-90 cm apart (depending on the variety) with rows 1.5-2 meters apart. Once seedlings have emerged and developed 2-3 true leaves, thin to the strongest plant in each group.

If starting seedlings indoors to get a head start, plant 2-3 seeds per pot, to a depth twice the size of the seed, 4-6 weeks before the last frost date. Thin to the strongest seedling. Biodegradable pots can be used to minimize root disturbance during transplanting. Harden off seedlings for a week before planting out by gradually exposing them to increasing hours of outdoor conditions. Transplant carefully, ensuring not to disturb the roots, and water thoroughly after planting.

After planting, apply a layer of organic mulch such as straw around the plants, avoiding the stems, to suppress weeds, retain soil moisture, and keep developing fruits clean and dry.

Cultivation

Consistent watering is essential for growing quality melons, particularly during flowering and fruit development. Water deeply at the base of plants rather than overhead, aiming to keep the soil consistently moist but not waterlogged. Irregular watering can lead to split fruits and poor flavour development.

Apply a complete organic fertilizer at planting time, and side-dress with additional fertiliser when the vines begin to run. You can switch to a fertiliser higher in potassium and phosphorus once flowers appear to encourage fruit development. A monthly foliar spray with seaweed solution; a mix of worm juice, seaweed and compost tea; or trace elements will help boost growth and resilience to pests and diseases.

Vines can be pruned. Once several fruits have started to develop, pinch out the growing tips to limit vine growth and direct energy to fruit production. For smaller varieties like ‘Sugar Baby’ watermelon, 2-3 fruits per plant is ideal, while larger varieties may only support 1-2 fruits per plant.

To prevent fruits from rotting where they contact the soil, place a piece of cardboard, a flat stone, or straw under each developing fruit. If growing vertically on trellises (more feasible with smaller melon varieties), provide support for developing fruits using cloth slings or old pantyhose.

Hand pollination may be necessary if bee activity is low. Use a small brush to transfer pollen from male flowers (those without a small swollen base behind the flower) to female flowers (which have a small swollen base behind the flower).

Harvesting

Melons typically take 80-140 days to mature, depending on the variety and growing conditions. The method for determining ripeness varies by type:

Watermelons are ready to harvest when:

The tendril nearest to the fruit stem has dried and turned brown
The underside of the fruit (where it contacts the soil) has changed from white to creamy yellow
The fruit produces a dull, hollow sound when tapped gently
The skin becomes harder to pierce with a fingernail

Rockmelons are ready when:

The stem begins to separate from the fruit (known as “slipping”)
The skin colour changes from green to tan or yellow between the netting
The fruit emits a sweet aroma, particularly at the stem end

Honeydew melons are ripe when:

The skin colour changes from green to creamy white or yellow
The blossom end yields slightly to gentle pressure
The fruit develops a sweet aroma

To harvest, cut the stem with a sharp knife rather than pulling the fruit from the vine. Leave a few centimetres of stem attached to the fruit. For best flavour, harvest in the morning when the fruits are coolest.

Once harvested, rockmelons and honeydew melons can continue to ripen and develop flavour for a few days at room temperature. Watermelons, however, do not continue to ripen after picking. All melons can be stored in the refrigerator after ripening for up to a week.

Problems

The best approach is to have a reliable Australian reference book to identify problems. Garden Pests, Disease and Good Bugs by Denis Crawford is recommended.

A general strategy to follow with any problem is to observe the plant carefully before taking action. Identify the problem then carefully consider the course of action. For example, with pest insects, you often can see a predator nearby. If you watch and wait the predator may deal with the problem for you. Beneficial predatory insects which feed on pest insects can be purchased from suppliers such as Bugs for Bugs. If the problem needs further action the above recommended book has suggestions.

Practicing good garden hygiene, crop rotation, and maintaining plant vigour by providing adequate nutrients are key strategies for prevention.

Melons can face several challenges:

Powdery Mildew: This fungal disease appears as white powder on leaves. Ensure good air circulation by proper spacing, avoid overhead watering, and apply milk spray (1 part milk to 9 parts water) or seaweed spray as a preventative measure. Select varieties that are less prone to powdery mildew.

Downy Mildew: Appears as yellow spots on upper leaf surfaces and grey-purple fuzzy growth underneath. Improve air circulation and apply copper-based organic fungicides for severe infections.

Wilting leaves during the day. It is common for the leaves to wilt during the day. As long as they perk up again in the evening it is not a problem. If not, you need to give them more water.

28-Spotted Ladybird: Unlike beneficial ladybirds, this pest damages melon leaves. Remove by hand and encourage beneficial predatory insects.

Aphids: These small sap-sucking insects can transmit celery mosaic virus. They often cluster on the undersides of leaves, causing distortion and stunting. Small populations can be controlled by washing them off with a strong stream of water or using insecticidal soap. Alternatively, neem oil or pyrethrin can be used. Beneficial predators like ladybugs and lacewings should be encouraged and can be purchased for release on the crop. Look for aphid mummies which are evidence that the aphid has been parasitised. Eggs can also be parasitised and will appear bronze in colour. Generally speaking, plants that are high in soluble nitrogen (nitrates and ammonia) are prone to attack by sap sucking insects. Ideally avoid using soluble nitrogen fertilisers and ensure plants have adequate trace elements. This can be achieved by using foliar sprays.

Fruit Rot: Can occur when fruits remain in contact with damp soil. Place a barrier such as straw or a flat stone between the fruit and the soil surface.

Inconsistent Watering: Leads to split fruits, blossom end rot, and poor flavour development. Maintain consistent soil moisture, especially during fruit development.

Poor Pollination: Results in misshapen fruits or fruits that abort before developing. Hand pollinate if bee activity is low, and provide flowering plants nearby to attract pollinators.

Recommended Varieties

To have success with melons in Canberra it is worth sourcing seed from early-maturing varieties to ensure fruits ripen before the cooler autumn weather arrives.

Watermelon:

Blacktail Mountain: The most cold-tolerant of watermelons – as the name suggests. Yields glassy dark, cannon ball-like 5kg fruit with sweet, succulent red flesh. The colour contrast of rich red flesh and near-black skin is picture perfect. Ideal for those wanting to try growing watermelons in Canberra.
Sugar Baby: An early-maturing “icebox” variety producing small (3-5 kg) melons with sweet red flesh and dark green rind. Matures in 75-80 days, making it ideal for Canberra’s shorter growing season.
Moon and Stars: An heirloom variety with distinctive yellow spots on the dark green rind. Produces medium to large fruits with sweet red flesh. Needs a longer growing season but can succeed with early planting.

Rockmelon:

Rosada F1 An early maturing melon with aromatic intensely flavoured deep orange flesh. Good disease resistance package. It makes a strong vine with high fruit numbers.
French Charentais: A petite-sized melon averaging 1- 1.3kg in weight with succulent firm orange flesh. It has a wonderful sweet flavour and highly fragrant aroma at maturity.
Hales Best: A reliable variety for Canberra with good disease resistance. Produces oval fruits with sweet orange flesh and characteristic netting. Matures in about 85 days.
Prescott Fond Blanc: A French heirloom with fragrant flesh concealed by the deeply furrowed and bumpy skin. Harvest in 14 weeks. 8 fruit per plant, 1.5kg per fruit.
Sweet Granite: An heirloom early to harvest melon features classic netted skin and firm, but flavoursome flesh. Early to harvest in just 12 weeks.

Honeydew:

Edens Gem: So delicious that Amy Goldman, author of Melons: A Passionate Grower’s Guide, commented that it ‘may cause drooling’! Neat 500g fruit are produced on early-maturing vines, ideal for cooler climates or impatient gardeners! Prolific. Harvest in 14 weeks.

References

Bubel, Nancy. The New Seed-Starters Handbook. Rodale Books, 2018.
Crawford D. Garden Pests, Disease and Good Bugs. Australia: ABC Books; 2015.
Dove, Helena. Botany of the Kitchen Garden, Kew Publishing, Royal Botanic Gardens Kew, UK, 2023.
Fanton, Michel and Jude. The Seed Savers Handbook. The Seed Savers Network, Australia, 1993.
The Diggers Club. (2021). How to grow Rock Melon and Cantaloupe. https://www.diggers.com.au/blogs/learn/how-to-grow-rock-melon-and-cantaloupe
Yates Australia. (2024). How to Grow Melons. https://www.yates.com.au/how-to-grow/melons/