How to tell if a watermelon is good?

In this brief guide, we will answer the query, “How to tell if a watermelon is good?” and will discuss some tips to properly pick the watermelon.

How to tell if a watermelon is good?

Watermelon fruit have few external indicators of ripeness. Unlike tomatoes, there is no color break visible on watermelon rind, and the plethora of rind patterns and colors makes ripeness difficult to predict among genotypes and cultivars. Fruit circumference, weight and ground spot color could be helpful by determining the ripeness of watermelon (1).

To tell if a watermelon is good, identify the yellow spot on them. When watermelons lie on the ground, they attain a blotch. It’s ripe when this blotch becomes a creamy yellow. Give it a thump: Tap the watermelon’s underside with your hand. One with a deep, hollow sound indicates that it has reached its optimum maturity and is full of juice.

Tips to pick a good watermelon

Fruits like watermelon, which are bright red and deliciously juicy, are packed with nutrients and are a great low-calorie option for a snack. There are several health advantages associated with the consumption of lycopene when it is at its ripest, including the prevention of heart disease and diabetes as well as some forms of cancer.

It’s typically only after you purchase a watermelon that you can determine whether it’s ripe by tasting or inspecting its crimson flesh. Picking a juicy and delicious watermelon based solely on its appearance might be a difficulty if you don’t want to use pre-cut items.

Number of subjective systems have been used by growers, to predict watermelon ripeness, including ground spot yellowness, senescent tendril next to the fruit pedicel, change in fruit wax (loss of shine), and thumping (dull sound when fruit are rapped with the knuckles). None of these harvest cues apply to all genotypes, because smaller types tend to sound different from larger types, and senescent tendrils may yield overripe watermelons for some. However, they are very trustful indications (1).

To ensure that you bring home a juicy watermelon, here are six recommendations.

Look for a uniform shaped watermelon

Shapes for watermelons range from round to oval to long and narrow. All of them are decent options. Stick to the ones that are solid and symmetrical, and avoid those that have bumps, dents, or cuts that are out of place. It is possible that the watermelon was pollinated incorrectly or got irregular quantities of water. However, wounds or dents might indicate the presence of insects or fungi.

Lift the watermelon up

It’s normal for a large, ripe watermelon to be rather weighty for its size. As a result, it’s juicier since it’s more water-filled. Water and fiber levels in fruits, especially watermelon, seem to influence a fruit’s healthy weight.

Watermelons are 91% water, which is why they’re called watermelons. Water-rich foods like watermelon may help you feel fuller while ingesting fewer calories by increasing the amount of water you consume per serving.

During the latter half of fruit development, sucrose accumulates as the number of enlarged cells increases. As internal cells enlarge, there is an increase in fruit weight and diameter. Sugars and organic acids accumulate in the heart and blossom end of watermelons as they advance toward maturity (1).

Check out the field spot

Ground spot, the portion of the rind in contact with the soil, changes color over time and may be a useful indicator of watermelon maturity. As chlorophyll content in watermelons decreases, carotenoids and anthocyanins, measured changes in yellowness/blueness become more prominent. With the fruit maturation, yellow is more evident (1).

To identify the field or ground spot on a watermelon, just flip it over and you’ll see a yellow spot. In this location, you can see the site where the watermelon lay before it was plucked. Having a huge, yellow mark on the fruit implies that it was ripened for a longer period and should be more flavorful.

However, a whiter patch indicates that it was harvested too early and didn’t develop to its full potential. Choosing a watermelon with a whiter area suggests that you will most likely end up with watermelon with a bland taste.

Tapping method

Another technique to tell whether a watermelon is ripe is to listen to the sound it produces when tapped or slapped. Even though this approach is subjective, watermelon fans are a big fan of this one.

Even more importantly, its popularity led researchers to create a vibration analysis that has been demonstrated to accurately determine ripeness. You should be able to hear a tenor-like sound when you hit a ripe watermelon with your palm or fist. It’s probably overripe if it sounds hollow or flat.

However, scientists claim that this method is prone to human factor errors; it may be a good way only for people with much experience and only low determination coefficients of correlation coefficients were obtained during experiments. Environmental conditions like temperature, air pressure etc. also affect the results (2).

 Determine the stiffness of the watermelon

Watermelon firmness refers to the rind or skin’s resistance. The flesh firmness is an important indicator to detect ripeness of watermelon. The watermelon ripening process results in loss of water in fruit cells and change of cell wall materials to soluble solids. The amount of total cell wall polysaccharides and starch decreased by 80% during ripening, which indicates that a decrease in the molecular weight of xyloglucan correlates with a loss in fruit tissue elasticity, while the changes in the molecular weight of pectin corresponds with changes in viscosity (2). The rind of a ripe watermelon should be thick and not readily pliable. In general, those that do tend to be overripe. With your fingernail, you shouldn’t be able to cut through the material.

Check the tail

Tail refers to the portion of the stem that remains after harvesting a watermelon. The stem links the plant’s leaves, blooms, and fruit to its roots by transporting water and nutrients. When a watermelon has a green stem, it’s likely that it was picked too early and will not be ripe. An unripe watermelon may be identified by its dry stem.

Studies done on seeded, large watermelons indicate that vine tendril proximal to the stem-end attachment may be the most useful indicator of maturity at harvest. A green non-wilted tendril indicates that maturity has not been attained, whereas a wilted but not fully senescent tendril may indicate commercial maturity has been reached (1).

Spot watermelon damage or spoilage with these tips.

It is possible to consume watermelons that have been harmed or have gone bad. Post-harvest deterioration of watermelon is linked to the activities of pathogenic fungi (A. flavus, Streptomyces spp. and F. oxysporum). Factors such as agrochemicals, rainfall, poor soil drainage, insect attacks, inappropriate harvest, transport, packaging and storage of watermelon fruits could contribute to post-harvest rot of watermelon. Mycotoxins produced by pathogenic fungi invasion on fruits could result in several diseases such as hypersensitivity and psychological disorder in man (3).

Signs that watermelon should be avoided include the following: 

·         Spots in a dark tone: These patches may be caused by fungus or bacteria.

·         Flesh drenched with water: The watermelon’s flesh starts to deteriorate, slump, and become black as this occurs. Fungal infection or oversaturation with water might be to blame.

·         Target cluster: Viruses may be responsible for these target-like settings.

·         Rind worm injury: An uneven white to the light brown pattern may be seen on the rind of the fruit, which may be produced by insects.

·         Internal cracks in the rind: This is a bacterial condition that causes the rind to become dark or tan.

·         Tangy or sour aroma: When the meat has begun to ferment, it emits a variety of unpleasant odors.

Other FAQs about Watermelons that you may be interested in.

Does watermelon have acid?

Does watermelon give you diarrhea?

Can You fry watermelon?

Can you eat watermelon seeds straight from the fruit?


In this brief guide, we answered the query, “How to tell if a watermelon is good?” and discussed some tips to properly pick the watermelon.


  1. Vinson, Edgar L., et al. Use of external indicators to predict maturity of mini-watermelon fruit. HortScience, 2010, 45, 1034-1037.
  2. Abbaszadeh, Rouzbeh, et al. Nondestructive determination of watermelon flesh firmness by frequency response. LWT-Food Sci Technol, 2015, 60, 637-640.
  3. ODELADE, Kehinde Abraham, and Oluwole Solomon OLADEJI. Isolation of phytopathogenic fungi associated with the post-harvest deterioration of watermelon fruits. Scient Afri 8, 2020, e00366.

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Hi, I am Charlotte, I love cooking and in my previous life, I was a chef. I bring some of my experience to the recipes on this hub and answer your food questions.