Crimson Sweet Watermelon

Citrullus lanatus

Also known as: Crimson


A classic large watermelon and one of the sweetest of the mainstream open-pollinated cultivars — oval-round fruit weighing 9–13kg with a pale green rind boldly striped in dark green, and deep crimson flesh that's crisp, juicy, and high in sugar. Seeds are small and dark, well-scattered through the flesh rather than clumped, which makes it a pleasant eating melon straight off the picnic table. Vigorous, dependable, and reasonably resistant to the wilts and rots that catch out fussier varieties. The benchmark against which most other watermelons are still measured. Sprawling vine — needs serious room to run.

Days to harvest 80–95 days from transplant
Fruit size Large oval-round fruit, 9–13kg
Sowing depth 2cm
Germination 6–10 days at soil temperature 21–30°C
Spacing 1–1.5m between plants, rows 2–3m apart
Aspect Full sun; deep, well-drained sandy loam rich in organic matter
Frost tolerance Sensitive to frost at both ends of the season — sow after last frost, harvest before first frost

Growing notes

A warm, sunny position with sandy, free-draining soil suits it best. Watermelons want heat, room, and steady moisture through fruit set.

Soil preparation: Deeply worked beds with generous well-rotted compost and aged manure. Watermelons are heavy feeders — build the bed before sowing and top-dress as the vine takes off.

Sowing method: Sow 2–3 seeds per station 1–1.5m apart, either direct into warm soil or into large pots for transplant, then thin to the strongest seedling per station.

Support: Left to trail along the ground. The heavy fruit is best rested on a small bed of straw to keep the underside clean and dry, and to reduce the risk of soil rot on ripening melons.

Watering & feeding: Deep, consistent watering at the base through vine growth and fruit set. Overhead watering invites mildew. Ease off water as fruit approaches ripeness — a drier finish concentrates the sugars. Side-dress with well-rotted manure or a balanced liquid feed once flowering starts.

Harvest: Watermelons don't ripen further once picked, so read the plant. Three signs together mean it's ready: the tendril nearest the fruit has dried and browned, the underside where the fruit sits on the ground has turned from white to a warm cream-yellow, and the skin has lost its glossy sheen for a matt finish. A dull thump on tapping is the traditional confirmation.

Timing: First ripe fruit around 80–95 days from transplant.

Key features

  • Large fruit 9–13kg with striped pale-and-dark-green rind
  • Deep crimson flesh, crisp and very sweet
  • Small, well-distributed seeds
  • Dependable cropper with useful wilt and disease tolerance
  • One of the most reliable watermelons for home gardens
  • Long-cropping vine once fruit set begins

Short season tips


Sow indoors in seedling pots 3–4 weeks before your last frost and transplant carefully — watermelons resent root disturbance, so use larger pots and minimise handling. In Coonabarabran and similar inland zones, plant out from mid-November once soil is reliably warm. Black weed mat under the vine warms the soil and buys extra ripening days at the tail end of the season.

  • Spring
  • Summer
  • Fall

Annual

  • Corn, bush beans, radish, nasturtium, marigold, oregano
  • Potatoes, other watermelon varieties within cross-pollination distance if saving seed


Developed at Kansas State University and released to the American seed trade in the mid-1960s, Crimson Sweet quickly became the standard-bearer for large sweet watermelons and remains in wide cultivation today. Now well past the fifty-year threshold, it is treated as an open-pollinated heirloom by most seed-savers and remains one of the most widely grown watermelons in home gardens around the world — kept alive by sheer reliability and by the depth of colour and sweetness in the finished fruit.