How To Grow Watermelon

Where Best to Plant

When choosing where to plant your watermelon in your home garden or raised bed, keep in mind that this fruit does best in loamy, somewhat sandy, well-drained soil that is slightly acidic (soil pH between 6 and 7).  In addition, watermelons are heavy feeders, meaning they need soil that is fertile and has a high nutrient level (for instance, add compost, seaweed or manure).  Space plants about 2 to 5 feet (60 to 150 cm) apart in raised rows or mounds to ensure good drainage, leaving 7 to 10 feet (2 to 3 m) between rows.  These plants require a lot of space as the vines can grow as long as 20 feet (6 m) in length (just like their pumpkin cousins!)  As the name suggests, this fruit needs plenty of water.  From planting until fruit begins to form ensure plants get 1 to 2 inches (2.5 to 5 cm) of water per week.  Soil should be moist but not water-logged and plants should be watered at their base.  Mulch around the base of plants once they reach 4 inches (10 cm) tall to slow weeds, aid in moisture retention, and keep the soil cooler.  Once the fruit is growing, watering can be reduced.  If fertilizing, in the beginning use a nitrogen-based fertilizer to encourage leaf and vine growth but then switch to one with less nitrogen (such as a phosphorus fertilizer) after flowering begins, to encourage flower and fruit growth.

With these plants, pollination is key.  Watermelon vines produce both male and female flowers separately on the same plant.  Typically, male flowers appear several weeks before female flowers (fashionably late to make an entrance!).  The female flowers are distinctive as they have a swollen bulb at the base and will be the ones to eventually bear fruit.  In order for this to happen, pollination needs to occur so “bee” kind to the bees (for instance, consider planting companion plants that attract bees!)  However, if you need to, you can always encourage fruit production by pollinating by hand.  First thing in the morning after flowers have opened, use a cotton swab or small paint brush to gently remove pollen from the male flower and transfer to the female, placing the pollen on the stigma (the raised area in the centre of the open female flower). 

Once fruit begins to grow and is ripening, you can help prevent rotting by gently placing a piece of cardboard or straw between the fruit and the ground.

If you want to grow seedless watermelons, there are a few things to keep in mind.  The seeds don’t germinate as well so start more seeds than you think you’ll need to ensure you get a few good ones.  Other than that, follow the same steps as previously discussed.  However, seedless watermelons need pollen from a seeded variety in order to produce fruit so you’ll have to plant both kinds near each other.

If you have a small garden and space is limited, you can also grow watermelon in containers.  To begin, it is important to choose a pot with lots of drainage holes that is large enough to accommodate the growing plant (5-gallon or 19 kg).  Fill with potting soil or other soilless mix and most importantly choose a variety well-suited for pots, one that is compact and grows small fruit.  Plant the seed and water well.  Add a trellis or teepee so that the vine will grow upwards and not take up an enormous amount of space.  If there aren’t enough pollinators in your area (especially if high up on a balcony), you may need to pollinate by hand.  Once the fruit starts to grow, you will need to provide additional support such as a hammock under the fruit made of a stretchy, flexible material (think pantyhose).  Water daily and twice daily if temperatures rise above 80 °F (27 °C).  Use a granulated slow-release fertilizer once a month or water-based fertilizer weekly.