A bright red watermelon quarter sits on the ground.

Agence Estudi/Getty Images

When you think of a watermelon, you probably picture a large, oblong-ish fruit with alternating light and dark green stripes and a juicy pinkish-red inside, dappled with black seeds. But watermelons actually come in a ton of varieties, many of which don't fit that description. Some have orange flesh or a yellow rind. Some are small or super long. Some have red or white seeds, instead of black, or no seeds at all. With more than 1,000 varieties, the watermelon is a diverse fruit, and one of the true varietal gems is the Black Diamond.

Black Diamond watermelons can be recognized by their deep, dark green skin and particularly large size. While most watermelons are already big, Black Diamonds are giants, generally clocking in between 35 and 50 pounds (compared to an average watermelon at 20 pounds). Crack them open to find vibrant red flesh void of black seeds, described by taste-testers as juicier and much sweeter than other watermelons. One person called them "candy-sweet."

Backyard gardeners can grow this specialty watermelon, if they can accommodate vines that reach 20 feet long. The melons need direct sunlight and a lot of time to grow, as they take about 90 days to mature. Ripe Black Diamonds should have a yellow underside (from being on the ground for so long) and dead tendrils near the fruit.

Where to get a Black Diamond watermelon — and what people think of them

A bunch of super dark green watermelons, some with large yellow spots, piled on top of each other.

Hemantmandot/Getty Images

If you're looking to try one of these for yourself, but would rather buy it than grow it, you can often find Black Diamond watermelons in stores, even though they aren't one of the more common varieties. Kroger sometimes carries the specialty melons, as do Ralphs and Harris Teeter. Redditors have also spotted them at Jewel-Osco, Sprouts, and others. 

Reddit reviewers noted that Black Diamond watermelons tend to be fairly pricey compared to other watermelons, but the cost might be worth it for the taste. One Redditor wrote, "Truly the sweetest and most delicious watermelon to ever exist. Proceed with caution, it will make other watermelon not taste good," while others said, "So sweet and juicy you'll think you died and went to heaven," and that it was "the best watermelon I've ever tasted!"

Some Redditors were concerned that the lack of seeds may affect the watermelon's flavor: "Every season the [seedless] quality continues to plummet. ... Black Diamond and every other seedless do not cut it." Others noted a lack of flavor, with someone reporting their melon was "as bland as a regular, bland watermelon." But flavor discrepancies could come down to an issue with an individual melon. After all, regardless of the type, sometimes you get a really good watermelon, and sometimes you get a really bad one. A watermelon's appearance and texture can provide a good hint about its quality, but even a best guess can be wrong.