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Black watermelons can get quite big, typically reaching between 15 and 30 pounds, though some exceptional ones can grow even larger under the right conditions.
When you’re asking how big do black watermelons get, the honest answer is that it depends on the variety, the growing conditions, and how long you let them mature on the vine.
Most black watermelon varieties, like the popular Black Diamond, tend to land somewhere in the 20 to 30 pound range when fully grown.
In this post, we’ll dig into exactly how big black watermelons get, what factors influence their size, and how you can tell when one is ready to pick.
Let’s dive in.
How Big Do Black Watermelons Get?
Black watermelons generally grow to be larger than many people expect, and the size really does vary depending on the specific type you’re growing.
Here’s a breakdown of how big black watermelons get and what you can realistically expect.
1. The Average Size of Black Watermelons
On average, a fully mature black watermelon weighs somewhere between 15 and 30 pounds.
That’s a pretty wide range, and it’s because the size of black watermelons depends heavily on the cultivar you choose.
Smaller black watermelon varieties might top out around 12 to 15 pounds, while the bigger ones can easily push past 25 pounds.
2. The Giant Black Diamond Variety
The Black Diamond is probably the most famous black watermelon out there, and it’s known for getting big.
These bad boys regularly reach 30 to 50 pounds when grown well.
Some gardeners have reported Black Diamonds tipping the scales at over 75 pounds, which is honestly massive.
So if you’re wondering how big do black watermelons get when it comes to the Black Diamond, the answer is seriously big.
3. Other Large Black Watermelon Types
There are other dark-skinned varieties like the Moon and Stars and the Blacktail Mountain that also grow to impressive sizes.
Blacktail Mountain tends to be a bit smaller, usually landing around 10 to 15 pounds.
Moon and Stars, on the other hand, can grow to about 20 to 40 pounds depending on care.
So the size of black watermelons really runs the gamut from modest to enormous.
What Determines How Big Black Watermelons Get?
Several factors play a role in how big black watermelons get, and understanding them helps you grow bigger fruit.
1. Sunlight and Warmth
Black watermelons need plenty of sun and heat to reach their full potential.
These melons thrive in long, hot summers with at least six to eight hours of direct sunlight daily.
The more warmth they get, the bigger black watermelons tend to grow.
2. Water and Soil Quality
Consistent watering and nutrient-rich, well-draining soil make a huge difference in how big black watermelons get.
Watermelons are heavy feeders, so they need healthy soil with plenty of organic matter.
Irregular watering can stress the plant and stunt the fruit, keeping your black watermelons smaller than they could be.
3. Vine Health and Spacing
A healthy vine with plenty of room to sprawl will produce bigger black watermelons.
If plants are crowded, they compete for nutrients and water, which limits how big black watermelons get.
Giving each vine enough space helps the fruit reach its maximum size.
4. Time on the Vine
The longer a black watermelon stays on the vine, the bigger it can get, up to a point.
Picking too early means smaller fruit, while letting it fully mature gives you the biggest possible black watermelon.
How to Tell When a Black Watermelon Is Fully Grown
Knowing when your black watermelon has reached its full size helps you harvest at the right time.
1. Check the Field Spot
The field spot is the patch where the watermelon rested on the ground.
On a ripe black watermelon, this spot turns a creamy yellow color.
If it’s still white or pale green, the melon probably isn’t fully grown yet.
2. Listen for the Thump
Give your black watermelon a good thump with your knuckles.
A deep, hollow sound usually means it’s ripe and ready.
A dull thud often means it’s either underripe or overripe.
3. Look at the Rind and Tendril
A ripe black watermelon has a dull, slightly rough rind rather than a shiny one.
The curly tendril near the stem should also be dry and brown when the fruit is fully mature.
So, How Big Do Black Watermelons Get?
Black watermelons can get as big as 15 to 30 pounds on average, with some varieties like the Black Diamond reaching 50 pounds or more.
The size of black watermelons depends on the variety, sunlight, water, soil quality, and how long you let them grow on the vine.
If you give them the right conditions, black watermelons can get impressively large and reward you with a sweet, juicy harvest.
Hope this post has helped you understand exactly how big black watermelons get and how to grow them to their fullest potential.