Watermelon Plants & 28-0-3 Fertilizer

Watermelons like lots of water and full sun and don't compete well with other plants or weeds.

Watermelon is a picky plant which likes sun, heat and plenty of water (but not too much) and is quickly out-competed by weeds or other plants. A high phosphorous fertilizer will promote fruiting, and additional treatments of a nitrogen fertilizer will enrich the plant as is grows.

28-0-3 Fertilizer

To produce healthy fruit, watermelons need a high level of phosphorous in the soil.

28-0-3 fertilizer is 28 parts nitrogen, 0 parts phosphorous, and 3 parts potassium. This type of fertilizer is sometimes known as "weed and feed" and is often used on lawns to deepen green color and prevent weeds. While the high nitrogen content would be beneficial to watermelon plants, they need phosphorous to produce healthy fruit, so this type of fertilizer is not recommended.

Best conditions for watermelons

Watermelons like plenty of sun and water, and an acidic soil.

Watermelons like a soil pH of 6.0 to 6.5, which is adjusted after testing by adding lime. The University of Georgia 4-H recommends a 20-20-20 or 20-10-20 fertilizer at planting time. 30 to 60 days after planting, a fertilizer supplement is added in a ratio of four parts nitrogen to one part phosphorous. Watermelons need plenty of water to flourish--as suggested by their name--but too much water will suffocate them. Allow the soil to dry within one inch of the top of the ground before watering. Watermelon is not a good competitor, so controlling weed growth is important. Using black plastic over the soil can keep soil moist longer and control weeds at the same time.

Growing a good watermelon

Large, juicy watermelons are encouraged by handpicking the early small fruits off the vine.

Start seeds when soil is above 68 degrees Fahrenheit. Fertilize with a 20-20-20 fertilizer and plant in soil away from other plants to avoid competition and allow plenty of space. Watermelons produce separate male and female flowers and need to pollinate to produce fruit. Be sure there are bees or other pollinators in the area, or remove a male flower and brush it over a female flower to hand-pollinate. Some growers remove first fruits, which tend to be of poorer quality, in order to produce larger, juicier fruit later in the season.

References

• University of Georgia 4-H: Watermelon Growing Contest
• University of Oregon Horticulture Department: Watermelon
• The Essential Garden Guide: Grow & Care - Watermelon