Black Diamond Watermelon | Complete Guide to Grow and Care | Expert Opinion

Black Diamond Watermelons are named for their glossy, solid black-green rind. However, the flesh is cherry-red. The flesh is always tender and sweet, with 25 to 40 grayish-black seeds. It requires a long, warm growing season. It is a great variety, like Charleston gray watermelon and crimson sweet watermelon.

This black Diamond has its origin in Africa. Melville Dillon developed it in the 1940s. Some refer to it as Arkansas Black Diamond, which is believed to have developed years ago.

They are open-pollinated; thus, there is always a change in the variety year after year. This makes the plant species the most diverse one. However, if the pollens remain shared within the same species year after year, the plant will be true-to-type and is called Heirloom.

Melville Dillon

Melville Dillon | 1907-1993

Features and Properties of Black Diamond Watermelons

The following table shows the features and properties

Scientific NameCitrullus lanatus
Common NameBlack Diamond Watermelon
Native AreaAfrica
Plant TypeAnnual / Spreading, creepy, vine, can spread in length up to 20 feet
LeavesSlow releasing Potash and Nitrogen fertilizers
SK Units119000 SKU
AppearanceBlack-green rind, cherry red flesh
Light requirementGrow well after frost in full sun
Average Weight35 to 50 pounds (lbs)
Days to maturity/ When to harvestTime to maturity is about 90 days
Plant spacing7-8 feet
Planting TimeAfter frost days, in Spring and summer
Row spacing16-18 inches
SoilWell-drained with slightly acidic soil (pH 6.0)
Water / IrrigationFrequent irrigation (after each 5-7 days)
FertilizersAdd compost, well-rotten FYM, or Seaweed
Organic AmendmentsAdd compost, well-rotten FYM or Seaweed
Number of Seeds per fruitMore than 25
Nutrition ValuesVitamin C, Beta-Carotene,  Lycopene
Importance and UsesUsed as Dessert (cholesterol free)
Hardiness ZonesUsed as Dessert (cholesterol-free)

How to Grow Black Diamond Watermelon from Seeds?

Please follow the following expert opinions for planting and getting well-juicy melons.

Black Diamond Watermelons

Time to Grow

Early spring is the best planting time for these melons in the home garden and indoors. At maturity, they require heat. Thus, growing these in early spring will require 1.5 to 2 months of good warmth to get them perfectly ripe.

However, if you are in the North and want to enjoy farm-fresh black diamonds, you can grow these in the plastic mulch covering warm soil in the greenhouses. This mulch and greenhouse will trap air and keep the soil and atmosphere comparatively warm. The perfect time for growing Black Diamonds in the North is when peonies bloom. It is usually 2 weeks after the last frost. Sowing will be more than 80% successful in early summer when the temperature is 70°F

Sowing Methods

Consider the following cares

  • Soil should be well-drained.
  • Sow it ½ inches deep in the soil after the last frost in the well–drained garden soil.
  • Space seeds and rows at 3-5 feet as the plant is creepy and spreading in nature. Thus, give them proper room for it. They can spread up to 20 feet in radius.
  • Indoor sowing can be done 3-4 weeks earlier in a controlled environment.
  • Keep plant-to-plant distance as low as 18” with rows 5-8 feet apart.
  • Apply frequent irrigation as the plant is not drought-resistant.
  • Frequent irrigation is also recommended to get juicy and sweet flesh.
  • It is nutrient intensive, requiring the release of Nitrogen and potassium.

Use the humidity dome and seed trays where the weather is cold and frost is still around. Plant seeds in trays and shift in the field when the temperature is more than 70°F.

Flowers and Fruiting

It is monoecious, with both male and female flowers growing on the same plant. However, the male flower blooms earlier and dies. Female flowers bloom 2-3 weeks after the male flower. It has a small swelling at the base, indicating fruit initiation. The flowers are open-pollinated and require bees for successful pollination. If the weather is rainy during flowering, this may restrict the free movement of bees and other pollinators.

Keep fruits with straw bedding when they are the size of a football; otherwise, these will decompose in the moist, warm soil.

Harvesting and Storage

Watermelons are ripe after two weeks of pollination. At the time of harvesting, stop irrigation. This will help concentrate sugars in the fruit and make it sweet and flavored. How to tell that the black diamond is fully ripened is very important. However, my personal experience is guessing from the skin color is the best judgment.

Some of the gardeners can judge the picking time by knocking the melon. A low-pitched deep sound will confirm the maturity. However, perfection in this method requires time and experience to listen to multiple sounds.

Ripened Black diamond Watermelon

I have experience storing melons for 1-2 weeks without a refrigerator. However, a cool storage room will increase the storage time. If you have extra melons, cut them, make dice or balls, and freeze them for later usage.

Plant Cares

Plant of black diamond requires the following cares

  • Optimum Temperature – Sowing must be done after the frost when the temperature is more than 70°F.
  • Light – They perform well in early to mid-summer with plenty of sunlight.
  • Thinning – To maintain a plant-to-plant distance of 8 feet, thinning of the plant is done after 2 weeks of sowing.
  • Frequent Irrigation – The plant is drought-sensitive, so frequent irrigations are applied. Better to use sprinkler irrigation
  • Soaker Hose – to avoid over-watering, use a soaker hose to hold extra water. This will also help in preventing fungal diseases.
  • Irrigation in the early morning – Apply water early in the morning so that excess water can evaporate in the sun.
  • Control Weeds – Control weeds earlier in the growing season as it would be difficult to move around when the vines spread.
  • Fertilizers and Nutrients – Apply premium quality fertilizers. It is better to use granular fertilizer for slow release. Apply more nitrogen-based fertilizers at the early growing stage while applying potash and phosphorus-based fertilizers at maturity.
  • Straw Beds – Keep all the maturing watermelons on the straw beds to avoid direct contact with the soil. Cardboard can also serve the same purpose here, but it will not be economical.
  • Aluminum Foil – Use it to concentrate heat and light to speed up the ripening and maturity.
  • Baskets upside down – keep your ripened fruit safe from critters (hogs) by covering the fruits with weighted-down laundry baskets.
  • Diseases – Plant faces fungal attacks (Alternaria, Anthracnose, Blight Spots). Downy mildew (yellow or pale green) and powdery mildew (white powder, spots) are common in moist environments. Apply Fungicides after consulting extension services.
  • Insects – Aphid attack is common. Check the underside of the leaves frequently. Apply insecticidal soap. If there is an attack of beetles, apply rotenone (pyrethrum-based insecticide) to kill these beetles. However, never use broad-spectrum insecticides as they may kill bees (pollinators).
  • Trellising – It is not recommended as the fruit is as heavy as 50 pounds

What is Trellising?

Trellising is providing support to the vines.


Red-fleshy, sweet, and flavored black diamond watermelons have their origin in Africa. Melville Dillon discovered it in 1940. They grow through seeds and spread from 5-8 feet. Leaves are broad. They love to grow in bright sunshine. These melons have a life of up to 90 days starting from early summer or late spring. They require frequent irrigation and nitrogenous fertilizers at an early stage. Proper care can give maximum size and weight up to 80 pounds. Cover melons with foil to get early maturity. Guess the time to pick by the color or tendrils. They are rich in Vitamin C and serve as a dessert.

Black diamond Watermelon - Mature


You can buy watermelon from the nearby supermarkets and farm fresh stores. The price range for the red juicy flesh of watermelon depends upon the size. However, an average watermelon would be $3.0-4.5.

If the seed produced by open-pollinated flowers is the same year after year and the taste remains true-to-type, the seeds are called Heirloom Seeds.

Black diamond has beta-carotene and vitamin C. It is cholesterol-free. It is used as Dessert.

All heirlooms are open-pollinated; however, not all are heirlooms.

It is a fun game where greased black watermelon is placed in the swimming pool, and the contestants try to catch it.

A simple and easy way to tell whether it is ripe is to know it with the middle finger. The hollow sound will confirm that it is well ripen. Some experts also guess the ripening status by the tendrils near the melon fruit. This tendril will dry or turn brown if the watermelon has ripened.

The harvest time is early to mid-summer. However, you can pick it when the rind turns bright to dull green and the hollow knock sound is clear.

Pick the ripened watermelon. You can guess this by seeing the tendrils and rind color or by the hollow and deep sound of the knock.

Usually, a watermelon contains 25-40 seeds.

No, they are pollinated, produce fruits and seeds, and grow from seeds. Each fruit has 25-40 seeds in the red flesh.

A black diamond melon resembles a big football with variegated dark green strips.

Black diamonds are sweeter and more flavored than regular diamonds. Moreover, they are expensive and bigger.

It can grow up to 80 pounds in weight and is massive.

If you find white flesh instead of red inside the watermelon, you have chosen the wrong and unripe one. Please go for another.

These are open-pollinated and Heirloom. You can use their seeds for next season. However, Hybrid seeds are just F1 generation and can’t be used in the future.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *