Yummy, sweet, pink-hued watermelon is a flavorsome summer fruit that is thirst-quenching and delicious. It is native to tropical Africa and grows best in warmer climates.
But how do you know when to harvest watermelons? Generally, they will be ready to harvest 70 to 90 days after you planted watermelon seeds. Some varieties mature in 80 days or more and others, like Sugar Baby, in 70 to 75 days. So you need other clues that will identify when you have ripe watermelons.
Growing Watermelon at Home to Harvest
There’s nothing better than the taste of homegrown watermelons. And since growing watermelons isn’t difficult, everyone with enough space for a watermelon patch should give it a go.
We’ve provided comprehensive guidelines on when to plant watermelons in another article. But here is a quick guide to growing watermelons at home.
Growing Watermelons at Home
Unless you are planting your seeds indoors and transplanting seedlings, plant seeds outdoors from late spring to early summer. The temperature of the soil should be at least 70°F (21°C). To be safe, wait until at least two weeks after the last frost date.
Ideally, the soil pH will be between 6.0 and 6.8.
When planting or spacing seedlings, make sure they are 3-5 feet (1-1.5 m) apart. After planting, cover the seedlings with row covers to trap warm air and keep out insects.
Food & Water for Watermelons
It’s important to water watermelons constantly. Drip irrigation is the best option because it helps to prevent fungal diseases.
During the growing season, especially while your watermelons are flowering and setting fruit, they need about 1-2 inches (25-50 mm) of water every week. Keep the soil moist but take care not to let it become waterlogged.
Because watermelons take a long time to mature, it’s also best to feed them with a slow-release fertilizer throughout the growing season. Seaweed-based fertilizers work well.
If you switch fertilizer during the growing season, use a product that contains more nitrogen than phosphorus and potassium between planting and when the first flowers appear. After the flowers appear, switch to a fertilizer with less nitrogen and more phosphorus and potassium.
Watermelon vines produce male and female flowers. Usually, the male flowers appear first and fall off quite soon after they open.
Don’t panic, the female flowers will appear about a week later. You can tell the difference between them because the female flowers have a small swelling at their base and they bear fruit.
When the vines produce both male and female flowers, you can remove the row covers.
It’s best to keep ripening watermelons from making direct contact with the soil to prevent rot. Once the fruit is about 3.82 inches (9.7 cm) in diameter, put each melon on a piece of cardboard or bed of straw.
If you want to speed up ripening, setting fruit on a surface that reflects light (like aluminum foil) will do the trick.
How Do You Know When Your Watermelon Is Ready to Harvest?
Watermelon plants grow fast, but the fruit needs 70-90 days to mature before it’s ready for you to harvest. Most seem to ripen about a month after blooming.
While the actual time frame will depend on the variety of watermelon you have planted, this information will be printed on the seed packet.
At the very least, knowing how long it should take to ripen will give you some idea of when to expect your watermelons to be ready. There are some telltale signs that you can look out for to make sure that your watermelons are ripe and ready to pick.
Signs That Indicate Ripe Melons
Johnny’s Selected Seeds, a very old, established seed company, mentions three common signs to look out for.
Tendril & Skin Color
The tendril nearest to the point on the watermelon vines must be brown, shriveled, and clearly dead, even if the stem is still green.
The surface color of the watermelon skin will become dull and the bottom of the watermelon will turn yellow. The contrast in color between the stripy lines on the fruit will intensify.
This is the point where it rests on the straw-covered ground, known as the “field spot.” If it’s white or pale green, the watermelon isn’t ripe yet.
If you knock your watermelons with your fingers, Johnny’s Seeds suggests you will hear a “punk” sound rather than a “pink” or “pank” sound!
Many other people say that if you thump ripe watermelons you will hear a dull, hollow sound. That is widely known as the thump test.
If your watermelons aren’t ripe, when you do the thump test, you will hear a more metallic ringing noise.
If you’re not sure what to expect in terms of the thump test, try thumping a ripe watermelon in your local grocery store to get a better idea!
You can also try pressing on the fruit. If it seems to give a little, then it’s ripe. But don’t push too hard or you might bruise and damage the fruit.
Some watermelon varieties soften at the blossom end. Sometimes they develop what looks like a circular crack around the stem, just above the top of the watermelon.
Size can also be an indicator – but only if you are comparing fruit on the same vine. For instance, if one of your growing watermelons is a lot bigger than others, it’s more likely to be ripe than those that are a lot smaller.
There is also at least one app that you download to your cell phone that will tell you if your watermelons are ripe or not. All you do is place your mobile device against the fruit and tap it several times! Maybe it works, we haven’t tried it.
What Happens If You Don’t Harvest Watermelons?
Watermelons need to ripen on the vine because they don’t ripen once they have been picked. Of course, it is a big dilemma if your watermelons aren’t ripe and frost is imminent.
The problem is that if you harvest watermelons before they are ripe, they will lack color as well as sweetness. They might even be inedible. But, if you don’t harvest them, they will be likely to split open and/or rot.
You’re damned if you do (harvest) and damned if you don’t. But you could try to cover the fruit and protect it from the frost for a few days. After all, they usually ripen on the vine in about two weeks.
But that’s the only time you shouldn’t harvest watermelons.
Even if you have too much fruit on your watermelon vines, harvest all of it. Give what you don’t want to friends, family, or an organization that feeds the needy.
How to Harvest Watermelons?
Watermelons mature rapidly in hot weather. Once your first melon is ripe, the rest of your crop will ripen within the next couple of weeks.
We’ve talked about the signs that indicate ripe melons. When you notice some or all of these signs, limit watering to increase the sweetness of the fruit.
As they ripen you can harvest your crop progressively.
Watermelons aren’t difficult to harvest. All you do is cut the stem close to the fruit using a very sharp knife, leaving about two inches of the stem on the fruit.
Should You Wash Watermelons after Harvesting?
We have already said that it’s important to harvest watermelons when they are mature and ready to eat. Since watermelon doesn’t keep particularly well, and it cannot be successfully frozen, you’re not going to be storing it for very long.
We have also suggested that you put your watermelons on a bed of straw or a sheet of cardboard to prevent them from coming into direct contact with the soil. This is primarily to prevent them from getting wet and possibly rotting at this point.
If you’ve done the above, it’s unlikely that your watermelons are going to need much more than a wipe-down with a damp cloth after harvesting. If your watermelons do seem to need washing, you could hose them down, but be sure to dry the fruit thoroughly before storing it.
Can You Eat Watermelon Immediately after Harvesting?
Watermelons don’t ripen or sweeten after they are picked, so you certainly can eat them immediately after harvesting.
But you don’t have to. After all, if you have a good harvest with a whole bunch of watermelons ripening at the same time, you aren’t going to be able to eat all your ripe watermelons straight away.
The good news is that you can store watermelons for about 10 days as long as you keep them in a cool room and don’t cut them open. Once you cut them, it’s best to wrap the pieces in plastic and keep them in the refrigerator. They are likely to last for at least four days in the fridge.
Most people love to eat watermelon, but not everybody has the space to grow it. Even the small varieties take up quite a lot of space.
But if you do give it a try, you’ll find eating newly harvested watermelons will be a big treat.
In this guide, we have provided you with lots of tips that will help you recognize when to harvest watermelon. We have also chipped in a few tips on growing watermelons at home.
Good luck and enjoy!