How do I know when a watermelon is ripe?

Look for the field spot on the bottom to turn creamy yellow and the tendril near the stem to dry out.

Can I grow these in containers?

Yes, but you need a very large container and a sturdy trellis to support the heavy fruit.

Plant guide

Watermelon.

Citrullus lanatus

Pronounced sit-RULL-us la-NAY-tus

Also known as Afghan-melon, Water Melon, Watermelon, bastard-melon, dessert watermelon

Watermelons are vining plants that produce large, sweet, juicy fruits. They love warm weather and plenty of space to sprawl across your garden. You will need a long, hot growing season to get the best harvest.

Another photo of Watermelon — Photo by Karim Haddad (CC BY) via iNaturalist

At a glance

Care level: Moderate
Plant type: Annual vegetable
Light: Full sun
Indoor light: Direct sun
Water: Every 2 to 4 days
Mature size: 10 to 20 feet long
Growth rate: Fast
Hardiness: USDA 9 to 11
Bloom time: Mid to late summer

Care

Provide consistent moisture while the fruit is developing, but reduce watering as harvest approaches to concentrate sweetness. Watch for powdery mildew on the leaves and ensure the vines have plenty of room to spread. Harvest when the underside of the melon turns from white to a creamy yellow.

Watering: Keep the soil consistently moist but not waterlogged during the active growth phase.
Feeding: Apply a balanced fertilizer early in the season and switch to a low nitrogen formula once flowers appear.
Pruning: Trim back excessive vine growth if the plant is taking over your entire garden space.
Repotting: Watermelons are annuals and are typically grown directly in the ground rather than in pots.
Soil: Well draining, sandy loam
Soil pH: 6.0 to 6.8
Temperature: 18 to 35°C
Humidity: 40 to 70%
Drought tolerance: Moderate
Lifespan: Annual, typically 1 growing season
Deer and rabbits: Low

Signs it needs repotting

Roots circling the bottom of the pot
Stunted growth despite regular feeding

Safety

People: The plant is generally non-toxic, but ingestion of large amounts of seeds may cause minor digestive discomfort.
Children: The large, heavy fruits can pose a crushing hazard if not properly supported on a trellis or stable ground.
Contact allergens: Some individuals may experience mild skin irritation from the fuzzy, bristly hairs on the stems and leaves.
Airborne allergens: There is no significant evidence of respiratory allergies associated with this plant.
Edibility: While the flesh is delicious, avoid consuming the rind unless pickled or cooked, as it can be tough and difficult to digest.

How to identify it

Large, lobed, hairy green leaves
Long, trailing, vining stems
Yellow, funnel shaped flowers
Large, round or oval striped fruit
Sweet, red or pink flesh

Height: 0.3 to 0.5m
Spread: 2 to 4m
Leaves: green, deciduous
Flowers: yellow, 2 to 4cm
Fruit: green, striped, red, yellow, Late summer to early autumn

Common problems

Powdery mildew — A fungal infection that creates a white, dusty appearance on the leaves.
Aphids — Small insects that suck sap from new growth and can transmit viruses.

Growing it

Propagation: seed
When to plant: Spring
Overwintering: This plant is an annual and will die with the first frost, so there is no need to overwinter it.
In containers: It grows well in large containers of at least 20 liters, provided you use a strong trellis for support.

Direct Sowing

Wait until the soil is warm and all danger of frost has passed.
Plant seeds 2 to 3 centimeters deep in mounds of rich, well-draining soil.
Space mounds at least 1 to 2 meters apart to allow for spreading vines.

Planting aromatic herbs like dill nearby can help mask the scent of the vines from pests.

Grows well with

Radish — Radishes can help deter cucumber beetles that often plague watermelons.
Nasturtium — These flowers act as a trap crop for aphids and attract beneficial pollinators.

Keep away from

Potato — Potatoes compete heavily for soil nutrients and can harbor blight that affects cucurbits.

Similar species

Cucumber — They share similar growth habits and pest vulnerabilities.

Science

Family: Cucurbitaceae
Genus: Citrullus
Order: Cucurbitales
Class: Magnoliopsida
Native range: Tropical Africa
Conservation: This species is widely cultivated and not of conservation concern.

It thrives in hot, sunny environments with well-draining soil and relies on bees for pollination.

Value to wildlife: nectar source
Pollinators: bees
Uses: culinary fruit, juicing, pickling

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 8/9
Temperature: 8/9
Moisture: 6/9
Nutrients: 7/9

Taxonomy resolved against GBIF.

Questions people ask

How do I know when a watermelon is ripe?: Look for the field spot on the bottom to turn creamy yellow and the tendril near the stem to dry out.
Can I grow these in containers?: Yes, but you need a very large container and a sturdy trellis to support the heavy fruit.

Where the name comes from

The name Citrullus is a diminutive of Citrus, referring to the fruit's resemblance to a small orange, while lanatus means woolly, describing the fine hairs on the stems.

Good to know

Watermelons are roughly 92 percent water.
The heaviest watermelon on record weighed over 350 pounds.
Ancient Egyptians placed watermelons in tombs to provide nourishment in the afterlife.

Is your watermelon looking unwell?

This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.

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This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.