Learning Download: How to Grow Watermelon

From Seed to Harvest: A guide to growing watermelons.

Watermelon is a favorite summer treat that can be enjoyed raw, in a fruit salad or even made into a dessert pizza. The sprawling plant is fun to grow for families. Planting watermelons from seeds allows gardeners to handpick which sort of fruit they want, as watermelon comes in seedless, different colors, large and small varieties. Seedless is one of the more common plants, and although the fruit is not completely seed free, the seeds are small, transparent and edible.

To plant:

Watermelon seedlings are tender and do not handle frost well, so plant after the last frost date. Plant watermelons outdoors, or if the summer season is shorter, plant them inside up to four weeks before the last frost date. Sow seeds 1 inch deep. Watermelons grow best in mounds, so plant six to eight seeds per mound with mounds space 4 feet apart.

To grow:

Once seedlings appear, thin them to two or three per mound. When they are younger, watermelon plants require lots of water, up to 2 inches per week. They grow best in soil with a pH of 6.0 to 6.8. Pruning the plant is not necessary, but it may direct more energy to growing the fruits. If you choose to prune, remove the small vines that grow laterally. To prevent rotting, gently lift the fruit as it gets bigger and turn it. you can also mulch with plastic around the plants. Common pests include cucumber beetles and vine borers. To prevent these, use floating row covers but remove them once the plants begin to flower.

To harvest:

There are a few tactics to determine if a watermelon is ripe, and it is important to use them because once a watermelon is picked, it doesn’t ripen any further. One way to determine if a watermelon is ready to harvest is to check the bottom spot of the melon where it sits on the ground. If a watermelon is ripe, that spot will turn from white to yellow. Other ways to determine if a watermelon is ripe is to gently knock the rind with your fist. If it sounds hollow, it may be ready to pick. A third tactic is to examine the small vine tendrils near the fruit. If they have dried up from green to brown and are beginning to fall off, the watermelon is ripe.

The watermelon also may take on a dull look instead of a bright sheen when it is ready to harvest. To harvest, take a knife and cut the watermelon from the plant, cutting the stem close to the fruit.After harvesting, it is suggested to chill the watermelon prior to serving.

What watermelons crave:

Since watermelons have a long growing period and produce big fruits, they are heavy feeders. Prior to planting, amend soil with compost and a higher nitrogen fertilizer. Once vines begin to ramble, side dress plants with a 5-10-5 fertilizer and again once the melons are set.

Where to buy watermelon seeds:

You can find multiple varieties of watermelon seeds, some with the potential to reach up to 50 pounds or with a yellow or orange flesh at Urban Farmer.

Learning Download: Common pests and diseases: Watermelons

Common pests and diseases: Watermelons

When growing vegetables, it is always exciting to care for the plant throughout its growing phase and then harvest it for delicious recipes later on, but one thing to watch out for is pests and diseases. Different plants are susceptible to different types of pests and diseases, and it is important to make your self aware so you can keep a watchful eye and also take any preventative methods to keep your plants safe throughout their lifespan. 

Watermelons can fall victim to several different pests and diseases.


Some of the common pests affecting watermelons include aphids, cabbage loopers, cutworms and thrips.

Aphids are soft-bodied insects that bring problems to lots of plants. They create discoloration of the leaves, necrotic spots and stunted growth. Use tolerant varieties and only apply insecticides if there’s a high infestation. 

Cabbage loopers will eat small and large holes in the leaves, and they oftentimes cause extensive damage. The caterpillars are pale green in color and have white lines down the sides. To manage this pest, encourage natural enemies or apply Bacillus thuringiensis. 

Cutworms will cause the stems of the seedlings or even young transplants to be severed at the soil line. If the plant is older, irregular holes will be eaten in the surface of the fruit. To prevent this from happening, remove all crop residue from the soil, spread diatomaceous earth around the base of the plants and only use insecticides if absolutely necessary.

Thrips may cause distortion if there is a high population, or the leaves may appear silvery. Avoid planting watermelon near onions, garlic or celeriac because thrips can build up there. Another preventative measure is to use reflective mulch and apply insecticides if absolutely necessary.


Some of the most common diseases affecting melons, specifically watermelons, include anthracnose, Alternaria leaf spot, gummy stem blight and more.

Anthracnose will cause small, dark spots on crown leaves after the vines begin to run. This disease can be seedborne and it can affect all but the youngest leaves. Treat seeds, practice crop rotation and utilize the appropriate fungicides to prevent this disease.

Alternaria leaf spot causes round or irregular lesions on older leaves. This disease prefers wet conditions, and it is a fungus. It can be controlled by practicing crop rotation, destroying all crop debris after harvest and applying the appropriate fungicides. 

Gummy stem blight will cause irregular or round brown lesions on cotyledons or brown or white lesions on the crown of the fruit and on the stems. The fruit may even ooze a sticky amber substance. This disease favors warm, wet conditions. To manage this problem, be sure to use disease-free seed, treat seeds before planting them, rotate crops with other non-cucurbits to reduce the possibility of disease, reduce the crop residue and apply the appropriate fungicides when necessary. 

Learning Download: Watermelon Comparison Chart

Watermelon Comparison Chart

TypeVarietyDaysSizeColorDisease Resistance
DiploidSugar Baby**758-12 lbs.dark striped green rind, red fleshA, FW
DiploidAll Sweet**9025-30 lbs.green striped rind, red flesh
DiploidBlack Diamond**9030-50 lbs.dark green rind, red flesh
DiploidYellow Crunch9015-20 lbs.green striped rind, yellow flesh
DiploidSweet Princess**8520-30 lbs.light green rind, pink fleshA, FW
DiploidSangria8720-25 lbs.light green striped dark green rind, red fleshA, FW
DiploidCongo***8535-50 lbs.dark green striped rind, pink flesh
DiploidTendersweet Orange**8515-30 lbs.dark green striped light green rind, orange flesh
DiploidDixie Queen**8030-50 lbs.green striped light green rind, red flesh
DiploidCrimson Sweet**8515-30 lbs.green striped rind, red fleshA, FW
DiploidCharleston Grey**8325-36 lbs.light marbled green rind, red fleshA, FW
DiploidTop Gun8321-24 lbs.green striped rind, red fleshA, FW
DiploidMoon and Stars**10015-24 lbs.yellow speckled green rind, red flesh
DiploidOrange Crunch9015-20 lbs.green striped light green rind, orange flesh
Triploid/SeedlessTriple Gold Seedless788-10 lbs.light green striped rind, yellow gold flesh
Triploid/SeedlessHarvest Moon Seedless*858-13 lbs.dark green rind, pink flesh
Triploid/SeedlessSweet Trip Seedless**858-12 lbs.light green striped rind, red flesh
Triploid/SeedlessLittle Trip Seedless856-8 lbs.light green striped rind, red flesh
Triploid/SeedlessRound Trip Seedless7516-22 lbs.green striped rind, red flesh
Triploid/SeedlessTriple Crown Seedless8018-20 lbs.green striped rind, pink flesh

*All American Selection Winner
***AAS Winner/Heirloom