How to Grow Watermelon

Watermelons were first brought to North and South America by enslaved Africans who snuck some of their most prized seeds across the ocean on the gruesome journey. Once in the Americas, watermelon took hold and became a popular fruit for enslaved Africans, European colonists, and indigenous Americans alike. In fact, historical records show that by the late 1700s many of the tribes throughout the southeastern US were growing watermelon in their subsistence gardens.

It’s clear from this fruit’s history that wherever it lands it is treasured by the people who live there. Read on to learn the ins and outs of growing watermelon and you too can cultivate this beloved fruit.

Types of Watermelon

There are many different varieties of watermelon with unique shapes, sizes, colors, and flavors. As far as growing conditions to keep in mind, you’ll first need to distinguish between seedless and traditional watermelon.

Seedless watermelons are produced by crossing two watermelon varieties in a way that creates offspring with three sets of chromosomes (triploid) rather than the typical two. Most plants and animals with three sets of chromosomes are unable to reproduce successfully and in this case, the fruit doesn’t even produce seeds. Because they don’t have seeds, they’re inherently dependent on a plant breeder creating the triploid seeds and selling them into the market each season.

Traditional watermelons are much simpler to grow and you can save seeds from year to year to improve the varieties for your specific microclimate. Most home gardeners grow traditional seeded varieties of watermelon and this is what I would recommend.

Growing Conditions for Watermelon

As the name implies watermelon requires consistent water to thrive. They should be grown in soil that has good water holding potential so compost and organic-matter-rich soils are best. Like most fruiting plants they require full sun exposure (at least six hours/day) to produce a crop. They can be started in pots indoors in the spring, but you shouldn’t plant them outside until all danger of frost has passed. You can also plant them by seed directly in the garden, but again wait until after the soil has warmed and there is no threat of frost.

If you’re growing a seedless variety of watermelon you will need to plant at least one pollinator variety of watermelon among them to supply pollen to the female flowers of the seedless vines. For traditional seeded varieties, one plant is adequate to pollinate itself. Keep in mind that watermelons are dioecious, meaning their male and female reproductive organs are on separate flowers. Therefore they require intervention from pollinators in order to reproduce. This is just one more reason why maintaining beneficial insect habitats in your garden is key.

Pests and Disease for Watermelon

Watermelon is in the same plant family as cucumbers and squash and it shares many pests and diseases with these crops. Cucumber beetles can be a major problem in a watermelon patch, both from feeding on the plant and by spreading plant disease through their mouthparts and droppings. Hand-picking cucumber beetles can be effective for mild infestations, but if they’re out of control you should consider spraying with the organic pesticide pyrethrin. Avoid spraying this when pollinators are active because although it is an organic pesticide, it kills many different species of insect.

Leafminers are another major insect pest for watermelons. Because leafminers are burrowed inside of the leaves and protected from the elements, they are generally not susceptible to pesticides so hand-picking is your best defense. In our gardens, we scan for leafminer damage regularly and squish the larvae on site. This is very effective for us at the scale that we grow and will work well for most home gardeners.

On the disease side, watermelon is susceptible to bacterial fruit blotch, downy mildew, powdery mildew, and fusarium wilt. The best first line of defense for plant diseases is always genetic resistance. If you are able to find watermelon seeds labeled “fusarium wilt resistant” they will give you a huge advantage in that department. For varieties without genetic resistance, many of the most destructive watermelon diseases can be managed through moisture control. Planting the vines in an area of the garden that has adequate airflow and sunlight to prevent moisture from building up on the leaves is ideal. Eventually your plants will most likely succumb to some kind of fungal or bacterial disease, but the goal is to keep them alive long enough to produce a healthy crop of melons.

Harvest and Use of Watermelon

In my opinion, the most difficult part of growing watermelon is harvesting it at the optimal time. There’s a relatively small window between an underripe and rotten fruit where the melons are optimally ripe.

The best trick that I’ve found to date for identifying a ripe watermelon in the field is observing the white patch on the underside of the fruit. When this white patch begins to blush or turn yellow your fruit is likely ripe. The first leaf and tendril attached to the end of the melon are another indicator for ripeness. When they begin to turn brown and dry up you should consider harvesting your melons. The downside to waiting too long to harvest is that the fruit will eventually become overripe and crack open, exposing its sweet flesh to every insect and rodent within smelling distance.

As far as I know, there are no common methods for preserving watermelon and why would you when you can eat it fresh? At room temperature, ripe watermelon will last for about a week and they will last up to three weeks in the refrigerator (if you can find space for it).

There’s nothing quite like biting into a perfectly ripe, cool slice of watermelon on a hot summer day. If you enjoy the finer things in life and have some extra space in your garden, I highly recommend giving watermelon a try.