Bountiful Gardens

The Watermelon (Citrullus lanatus)

Watermelons are vining annuals that love two things above all else: blistering sun and consistent water. They are "solar converters," turning 100 days of sunshine into sugar-filled, hydrating fruit. On a patio, they can be grown as a "spiller" across the deck or trained up a sturdy trellis to save space.

Setting the Stage for Success

Soil & Fertilizer

Watermelons are "heavy feeders" because they have to grow 10–15 feet of vine and a 10-pound fruit in just a few months.

• The Soil: Use a large container—at least 15–20 gallons. They need a deep "reservoir" of soil to stay hydrated. Use a rich potting mix heavily amended with compost or aged manure.

• Feeding: Use a balanced organic fertilizer at planting. Once the vines are about 3 feet long, switch to a High-Potassium (K) fertilizer every 2 weeks to encourage flowering and fruit development.

Space Management

• The Sprawler: Let the vines trail across your patio. To protect the developing fruit from the hot concrete, place a "cradle" (like a piece of cardboard or a bed of straw) under each melon.

• The Climber: You can grow watermelons vertically! You will need a very heavy-duty trellis. As the fruit grows, you must support it using "slings" made of old t-shirts or nylon stockings to prevent the weight from snapping the vine.

Maintenance, Trimming & Troubleshooting

Pollination: The "Bee" Factor

Watermelons produce separate male and female flowers on the same plant.

• Male Flowers: Appear first on long, thin stems.

• Female Flowers: Have a tiny "mini-melon" at the base of the bloom.

• The Trick: If you don't see many bees on your patio, you can hand-pollinate by picking a male flower and rubbing its pollen onto the center of the female flower.

The "Water Cut-Off"

About one week before harvest, reduce your watering. This "stresses" the plant and causes it to concentrate its sugars, making the fruit much sweeter and less watery.

The "Is It Ripe?" Test

Harvesting a watermelon too early is a heartbreak. Look for these three signs together:

1. The Tendril: Look at the curly green tendril closest to where the melon attaches to the vine. When it turns brown and crispy-dry, the melon is likely ready.

2. The Ground Spot: The spot where the melon rests on the ground should turn from white/pale green to a creamy, buttery yellow.

3. The "Thump": A ripe melon should sound "hollow" or like a dull thud (though the first two methods are more reliable!).

Pro-Tip: The "Sugar-Elevator"

If you are growing your watermelon on the ground, place a terra cotta pot saucer upside down under the fruit. The terra cotta absorbs the sun's heat during the day and radiates it back to the melon at night, speeding up the ripening process and keeping the fruit away from pests!