When to Plant Watermelon in Cairns, Tropical Guide

Sow March to July. Right now in September it is out of season. The next sowing month is March.

Published · Last reviewed · By Garden Buddy
Growing advice is reviewed by hand. Planting dates, current conditions and prices on this page update daily.

This Watermelon guide is written for the Tropical zone, which takes in Cairns, Townsville and Darwin. Somewhere else? Your postcode picks the right one.

Not your zone? Brisbane Sydney Melbourne Canberra Alice Springs Perth

Also handy: will it frost this week? and what grows in shade.

Watermelon

Photo: Wikimedia Commons

Watermelon is a warm-season vine crop native to Africa, requiring long hot summers and ample space. Australia's arid interior and northern regions produce some of the sweetest watermelons in the world. Home-grown watermelon in warm zones is deeply rewarding. Requires substantial space (each vine can spread 3-4m), consistent warmth, and patience (80-100+ days to maturity).

Planting Calendar for Tropical

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
- - S S/T/D S/T/D S/T/D T/D - - - - -

S = Seed Tray   T = Transplant   D = Direct Sow

Want a nudge when it is Watermelon sowing time in Cairns?

One email a week with what is worth planting in the Tropical zone right now, Watermelon included, plus which veg has jumped in price at the supermarket. Free, and you can stop it in one click.

Current Growing Conditions

Soil temperature: 21.4°C (optimal range: 21–35°C) ✓ Ready to plant

Modelled from Open-Meteo forecast (Cairns), not a live sensor.

How to Grow Watermelon in Tropical Australia

When to Plant

Dry season: March-August. Thrives in tropical heat.

Soil
Sandy loam to loam, well-drained, enriched with compost. Sandy soils warm fastest. Watermelons tolerate slightly sandier conditions than most cucurbits.
pH Range
6.0-7.0
Sunlight
Full sun (minimum 8 hours). More heat and sun = sweeter fruit.
Spacing
150cm apart, 250cm between rows
Watering
Deep regular watering during vine growth and fruit development. CRITICAL: reduce watering 2 weeks before harvest to concentrate sugars. Excess water at maturity dilutes sweetness and causes splitting.

Companion plants: Corn, Sunflower, Nasturtium, Radish (trap crop for flea beetles)

Avoid planting near: Potato, Other Citrullus if seed saving

Tropical Growing Tips for Watermelon

Recommended Varieties

  • Crimson Sweet
  • Sugar Baby
  • Moon and Stars
  • Charleston Grey

Key Challenges

  • Fruit fly
  • Anthracnose in humidity
  • Wet season growing impossible

Pro Tips

  • Prime watermelon country during dry season
  • Raised mounds for drainage
  • Net against fruit fly from fruit set

Harvesting Watermelon

When ready: Multiple indicators needed: 1) Tendril nearest fruit turns brown and dry, 2) Ground spot (where fruit sits) turns from white to creamy yellow, 3) Skin resists thumbnail scratch (hard rind), 4) Dull thud when tapped (not hollow ring). Use ALL indicators together. No single one is reliable alone.

How to harvest: Cut stem cleanly with sharp knife. Do not pull or twist. Handle carefully.

Worth growing?

A 2.4 m × 1.2 m bed fits 1 plant, about $14 worth at today’s Aldi prices, checked today.

That is roughly 4 kg at $3.49 a kilo.

Draw your watermelon bed → No account needed.

Where to next

What watermelon costs in the shops right now, retailer by retailer, updated daily.

Also worth sowing in the tropical zone this September: Lemongrass, Ginger, Cucumber and Basil.

The pest most likely to find your watermelon: Downy Mildew.

Supermarket Price

Current average retail: $3.49/kg (12-month range: $3.49–$3.99)

Grow your own and save on grocery bills.

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Common Questions About Watermelon

When do you plant watermelon in Australia?

It depends on your climate zone, not the calendar month alone. Planting months by zone:

Does watermelon grow all year round in Cairns?

No. In the Tropical zone the planting months are Mar to Jul. Outside that window it either bolts, sulks or gets cut down by the weather.

Which zone am I in?

Type your postcode into the box under the heading and the page tells you, and links this crop in your own zone if it differs. Or look it up on the grow zone map. This page is the Tropical zone, Cairns is its reference city.