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All About the Black Diamond Watermelon

The Black Diamond watermelon is one of the most unique and interesting melon varieties on the market. It’s loved by home growers and commercial farmers and is one of the most versatile watermelons.

A large, dark green rind watermelon.

If you’re curious and want to know more about growing this watermelon and how to use it, you’ve come to the right place. Keep reading to find out everything you need to know about the Black Diamond watermelon.

A Brief History

Black Diamond isn’t one of the oldest watermelon varieties, but it isn’t a recently developed hybrid either. It was first cultivated and developed in Arkansas by Melville Dillon.

A young, dark green watermelon similar to the black diamond watermelon.

While the melon was developed in the 1940s, it didn’t become popular or widely available until the 1950s, when it became a homegrown favorite. The Black Diamond watermelon isn’t quite as popular as other varieties but serves more uses than the average melon.

Characteristics of this Melon

Shape and Size

One of the first things you’ll notice about this watermelon is that it’s massive. On average, a full-grown Black Diamond watermelon can weigh anywhere from thirty-five to seventy-five pounds.

Some have even been recorded at over 100 pounds!

While the melon is bigger and heavier than the average Joe, it has the same roundish oblong shape typical of most melons. Black diamond watermelons are vine growers, and the vines can grow between fifteen and twenty feet long.

A watermelon plant with a small, dark green melon growing on the vine.

Internal and External Color

Aside from its massive size, another thing that sets Black Diamond apart from other melons is its skin. Unlike most watermelons that have dark green skin with stripes and striations, Black Diamond is a solid, dark green color.

The only hint of any color apart from dark green is on the side lying on the ground. This side will turn yellow as the season progresses.

While black diamond melons may look different on the outside, they have the same crisp, red flesh typical of most melons. Since they’re an heirloom variety, black diamonds will also have an abundance of black seeds throughout their flesh.

Taste and Texture

Another reason black diamond watermelons are so popular is their delicious taste. Their red flesh is juicy, crisp, and sweet to the taste, and they’re a favorite for large gatherings because of their size.

However, black diamond watermelons can be a bit tricky when it comes to getting the perfect taste. Because of how big they are, it’s tough to harvest the melon at the perfect time when the outer and inner flesh tastes the same.

If you harvest it too early, the outer layer of flesh will be crunchy but unsweet and unripe. However, if you wait too long, the outer flesh will be perfect, but the middle of the melon will have overripened and be nearly rotten.

Health Benefits

Like all watermelon varieties, black diamond watermelons are a healthy snack and offer several benefits.

  • Vitamin C
  • Potassium
  • Cartenoids
  • Lowers cholesterol
  • Contains water

Alternative Uses for Black Diamond Watermelons

In addition to being healthy to eat, black diamond watermelons also serve several alternative uses, some of which are healthy. The plant and fruit of the melon get utilized to create natural soaps, essential oils, cosmetics, and other health and beauty products.

When it first hit the market, this melon was also the perfect size for what Arkansanians referred to as a greased watermelon contest. Basically, someone would grease up one of these melons and drop it into a pool or pond, and contestants would compete to see who could catch it first.

Growing At Home

These melons are fairly easy to grow if you properly plant and care for them. They perform best in hardiness zones four through nine, but they have also succeeded in zones two, three, ten, and eleven.

A dark green watermelon.

Timing is everything when you’re planting black diamond watermelons (our Watermelon Planting guide will walk you through what you need to know). Planting them too early could mean that the soil isn’t warm enough, but waiting too long could lead to freezing temperatures.

Because of how big black diamond watermelons are, they take longer to mature than most other varieties. While the average melon takes between sixty and eighty days to reach maturity, black diamonds can take upwards of ninety.

Along with its lengthy mature time, here are a few other things to keep in mind if you want to grow black diamond watermelons in your garden. grow this variety at home. However, if you’re feeling ambitious enough to try them, our guide on How to Grow Watermelon will provide a full picture of what it takes to grow watermelon.


Ideally, you want to wait to plant your black diamond watermelons until the soil temperature is above 70 degrees F. This watermelon variety isn’t very hardy against cold temperatures, so you also want to wait until the daytime temperatures are between 65 and 95 degrees F.

You should also ensure that these melons get planted in soil that’s slightly acidic, rich in nutrients, and has a loamy texture. Watermelons require a ton of water, which means they need soil that has excellent drainage but retains moisture when necessary.

These melons also need plenty of potassium, magnesium, and phosphorous, so using a fertilizer is a good idea. To help you figure out which one to get, we’ve got an article all about Watermelon Fertilizer. Additionally, you should add several inches of nutritious mulch around your watermelon plants.


Black diamond watermelon vines can grow anywhere from fifteen to twenty feet long, so proper spacing is essential. These melons can also grow up to twenty inches long and have a diameter of up to six feet.

Closeup of a watermelon plant blossom.

Therefore, you should space your seeds anywhere from four to six feet apart. You’ll need to add trellis supports if you want to grow them vertically.


You should prune your black diamond watermelon two times from when you plant it to when it reaches maturity. You only want four growing tips with these melons, so pinch back the least productive seedlings and allow the rest to flourish.


Watermelons, including black diamond, consist mostly of water. As such, they need a ton of water during the planting and growing process.

Water also helps watermelon plants grow leaves, which is what helps them produce sugar. So, the more water you give your watermelon, the sweeter and juicier it will be.

Ideally, you should use a drip irrigation system or a sprinkler system to water your watermelon plants. The soil should be constantly moist but never soggy to the point of muddiness.

Black diamond watermelons also need more water when you first plant them, and you can reduce their intake as they grow closer to maturity.


Like all watermelon varieties, black diamond loves itself some sunshine. You should plant your melons in full sun, where they are guaranteed at least six to eight hours of sunlight per day.

However, it’s better for them to get too much sun rather than not enough.

Pests to Watch Out For

Cucumber beetle
Cucumber beetles are notorious watermelon pests.

All watermelons tend to draw in pests and bugs, but black diamond is especially bad. They’re prone to attracting aphids, bees, predatory wasps, birds, beetles, rabbits, and other bugs and rodents.

You’ll want to be sure to read our Watermelon Pests blog post so you’re able to spot the signs of common pests and take quick action against them.

Common Watermelon Diseases

In addition to pests, there are various diseases to watch out for, including various forms of wilt, mildew, scab, and anthracnose.

But not to worry — our post on Watermelon Diseases provides the answers about how to identify and treat what might ail your plants, plus share best practices for reducing the risk of disease.

Harvesting This Watermelon

While planting and caring for black diamond watermelons is difficult, knowing how and when to harvest them is no picnic. Ironically enough, however, harvesting these melons could lead to one!

Most of these melons are ready to harvest roughly eighty to ninety days after you plant them, but you should start checking them around day sixty. We’ve got an article about When Watermelons are Ripe that will let you know what clues to look for to determine when your melons are ripe and ready to harvest.

  1. The tendril nearest the fruit will turn brown and shrivel up.
  2. The side of the melon that was on the ground should turn white or yellow.
  3. The fruit should sound hollow when you tap it.

Once you’ve got it in the kitchen, cut it up the right way to keep the mess to a minimum – learn how to cut watermelon sticks.

Check out our sister page for more information and clues about Best Ways to Harvest Watermelon for your black diamond watermelons.

Where to Buy Black Diamond Watermelon Fruit or Seeds

Two watermelon seedlings.

If you want to buy these melons after harvesting, you can find them at most southern fruit markets and select grocery stores.

If you want to buy the seeds, they’re available online at one of our favorite seed retailers, True Leaf Market.

Try a Black Diamond Watermelon for Yourself!

A bowl of watermelon slices.

The black diamond watermelon is one of the most unique and useful heirloom varieties. You can use it for anything from food to cosmetics to oils to food to attract deer and rabbits.

If this article has you curious about watermelon plants, you can find all the information you need on our sister page dedicated exclusively to watermelon plants.

Duane A. Cooper

Tuesday 13th of June 2023

Thank you, I cant find any Black Diamonds (with seeds) they just taste better than those seedless ones. In my opinion the Black Diamond is the best. they just have a sweet taste like no other melon. I am going to learn to grow them because I can never find them. The last one I found was at the farmers market in Forest Park Ga. Thanks again

Gary Beets

Tuesday 16th of May 2023

This article was very informative. I’m now ready to plant Black Diamond watermelons in my garden.