How to grow Watermelon (Sugar Baby)

Citrullus lanatus

🍓 Fruit 🌱 Grown each year

Small, round, dark-green watermelons with sweet red flesh — the best chance of a home-grown watermelon in a greenhouse or polytunnel.

At a glance: Sow mid March to early April, harvest from late July.

When to sow, plant and harvest

JanFebMarAprMayJunJulAugSepOctNovDec

Sow indoors

Plant

Flowers

Harvest

Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.

Growing Watermelon (Sugar Baby): what it needs

Light: Full sun · 6+ hours a day
Watering: Water regularly in dry weather
Soil: Fertile, well-drained soil
Spacing: 90 cm
In pots: Only in large containers
Feeding: A general feed before sowing or planting
Harvest: About 120 days from sowing
Hardiness: USDA zones 4–11
Difficulty: Intermediate

Step by step

Mid March – early April · 5 weeks before the last spring frost
Sow Seeds Indoors
Sow in modules or small pots of seed compost under cover. Sow on edge, 1 cm deep, at 20–25°C.
5–10 days after “Sow Seeds Indoors” · Mid March – late March
Check Germination
Seedlings should appear in 5–10 days. If sown outdoors, thin to 90 cm apart when big enough to handle.
14–21 days after “Check Germination” · Late March – early April
Pot On Seedlings
Move seedlings into 9 cm pots (or keep in modules) when they have their first true leaves.
Late April · 11 days after the last spring frost
Harden Off
Stand plants outside by day for 7–10 days before planting out.
Early May – early June · 3 weeks after the last spring frost
Plant Out
Plant out 90 cm apart and water in well.
14–21 days after “Plant Out” · Mid May – late May
Pinch Out and Train
Pinch the main tip after 5 leaves; train the side shoots and let each plant set 2–4 fruits.
30–45 days after “Pinch Out and Train” · Mid June – early July
Start Feeding
Feed every 7–10 days with tomato feed once the first flowers appear.
14–21 days after “Start Feeding” · Early July
Support the Fruits
Rest developing fruits on a tile or in a net sling so they do not rot or pull the vine down.
80–101 days after “Plant Out” · Late July – mid August
Start Harvesting
Watermelons are ripe when the curly tendril by the fruit dries and the pale patch underneath turns creamy yellow.
35–65 days after “Start Harvesting” · Late August – late September
Finish and Clear
Clear the vines after the last fruit.