Edible plant · fruiting

Watermelon

Citrullus lanatus

Also known asSandía · Wassermelone · Tang gua

intermediate warm-season frost-sensitive hydroponic-ready aquaponic-ready continuous

Use in garden planner Calculate nutrients

Days to harvest

75–100

Yield / plant

4kg

Spacing

180 cm

Daily light

25–35DLI

Environment

The bounded range this crop tolerates. Strict on light; outside the DLI band, yields drop sharply.

Temperature

5152535

21–32°C

45.578.5

6–6.8

EC (hydro)

01234

2–2.8 mS/cm

Daily light

5152535

25–35 mol/m²/d

!Light strict; fails outside DLI band

✓Continuous harvest

Climate and zones

USDA zones: 4–13 (winter low around -34°C)
Frost: frost sensitive (dies at first frost)
Season: warm (summer, frost-sensitive)

·Outdoor year-round (in zone)

✓Outdoor in growing season

✓Unheated greenhouse / hoop

✓Heated greenhouse

·Indoor (heated home)

·Indoor hydroponics + grow lights

Growing systems

Root mass: heavy. Thin-channel systems can't hold this crop.

·Deep water culture (rafts)

·NFT channels

·Vertical / aeroponic tower

✓Drip / Dutch buckets

✓Media bed (ebb and flow)

·Wicking bed

✓Soil bed

Growing media

Medium	pH effect	Retention	Bacterial surface
Coco coir (Coconut coir)	slightly acidic	high	moderate
Perlite (Expanded volcanic glass)	neutral / inert	very low	low
Soil-based mix (Potting soil)	varies	high	high

Nutrient demand by stage

NPK ratios are relative weights. EC targets shift through the plant's life.

Stage	N	P	K	EC (mS/cm)
seedling	2	1	1	1.4
vegetative	3	1	2	2
flowering	1	2	3	2.4
fruiting	1	2	3	2.6

Companion-growing notes

Heavy uptake of potassium, nitrogen. Co-grown crops with the same demand will end up deficient even at "correct" EC.
Very high transpiration. Reservoir drops fast; expect daily top-ups and EC creep.

Aquaponics suitability

Compatible

Fish waste provides enough nitrogen for healthy growth. Supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.

Care notes

A space-demanding vine crop for warm outdoor growing or large greenhouses. Use a Dutch bucket or large container (30 L) with a strong trellis for vertical growing of mini or personal varieties. EC 2.0-2.8 mS/cm. pH 6.0-6.8. Temperature: 25–35°C (among the most heat-demanding crops). Very high light (DLI 25-35 mol/m2/day). Hand-pollination is needed indoors. Mini varieties ('Sugar Baby', 'Crimson Sweet') are more practical for trellised hydroponic growing than full-sized types, and developing fruits should be supported in mesh slings. Each vine produces 2-4 mini melons or 1-2 large ones. From transplant to harvest: 70-90 days for mini types, 80-100 for full-sized. To judge ripeness, tap the melon for a deep hollow sound, check that the ground spot is creamy yellow rather than white, and look for the tendril nearest the stem to be brown and dry; reduce watering in the final week to concentrate sugars.

Notable varieties

Cultivar	Type	Days	Notes
Sugar Baby	open pollinated	75	Icebox-size (3-5 kg), the short-season home garden standard. Will grow in greenhouse vertical systems with slings. Reliable in zones 4-7 where larger types run out of season.
Crimson Sweet	open pollinated	85	Classic large round watermelon (10-15 kg), the variety most picnic watermelons descend from. Needs zones 6+ and a full 85+ day warm season.
Black Diamond	heirloom	90	Very large (15-25 kg), dark-skinned. Old Southern variety; what people picture when they hear 'watermelon.' Long season and heavy; not greenhouse-suitable.
Yellow Doll F1	hybrid	70	Yellow flesh, icebox-size, very early. The shortest-season watermelon available; works in zone 4 short summers where Sugar Baby is marginal.