Watermelon Growing Guide: from seed to kitchen

How to Grow Watermelon

The essential guide to growing Watermelon  (Citrullus lanatus) from seed; with notes on germination, cultivation, harvest and even kitchen uses. 

A quick taste-tour of the tribe:

• Seeded & Picnic: classic red flesh, black seeds, the summer barbecue icon (eg. ‘Crimson Sweet’).
• Seedless: extra-sweet, crisp, easy for kids (these triploid varieties also need seeded plants for proper pollination).
• Icebox: small 2–4 kg fruit that fits the fridge and ripens a little earlier than bigger varieties (eg. Sugarbaby).
• Yellow & Orange-fleshed: tropical-fruit flavour, great for salads and vivid sorbets.
  

Kitchen uses range from chilled wedges, granitas and juices to pickled rind and grilled “steaks”.

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Ave. Seeds per Gram: ≈ 7 – 12 seeds / g

Germinating Temperature: 24 – 35 °C (ideal 28–32 °C) — sprouts in 4–8 days if soil is warm and moist.

Feed Requirements: 

• Heavy feeder.
• Dig in well-rotted compost plus 5 kg/m² of aged manure before planting.
• Side-dress with a complete organic fertiliser at early running and again when fruit set.

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Growing Notes:

Climate & Timing

• Needs consistently warm weather.
• In most of temperate Australia direct-sow or transplant from late spring once soil reaches 18 °C; in the tropics sow during the drier, cooler months.
• In cooler areas chooser smaller varieties (eg. Sugarbaby) and start seed undercover and on a heat bed 4 weeks before planting out. This protects the seedlings from cooler nights.

Spacing & Depth:

• Sow 2 seeds 2 cm deep every 80 cm along rows 2 m apart, then thin to the strongest. In cooler areas start indoors (see above).
• Give vines room to sprawl or train on sturdy trellises with fruit supported in slings.

General Care:

• Mulch thickly to conserve moisture.
• Irrigate deeply but infrequently to promote deep roots, reducing water 7-10 days before harvest for best flavour. 
• Pinch out after 3–4 fruit per vine for larger melons.

Common Problems & Pests:

• Powdery mildew and downy mildew — improve airflow, use sulphur sprays.
• Fruit fly — net young fruit or bag individually.
• Aphids → transmit watermelon mosaic virus — control early.
• Poor set on seedless types — always interplant ⅓ seeded pollenisers.

Harvesting Notes:

When to Harvest:

Look for the adjacent tendril to turn brown and dry, the skin to dull and resist a fingernail, and a deep “thunk” when tapped.

How to Harvest:

Cut the stem cleanly with secateurs rather than yanking to avoid vine damage.

Storage & Use:

• Whole fruit keep 1–2 weeks at 10–15 °C.
• Chilled, cut pieces last 3–4 days.
• Freeze cubes for slushies or dehydrate into “melon jerky”.

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Key Benefits (both crops):

• Rich in vitamins A & C, hydration superstar.
• Sprawling vines shade soil, suppressing weeds.
• Perfect companion for kids’ gardens — nothing beats slicing open a melon you grew yourself.

Happy sowing, and may your summer harvest be the juiciest on record!