When to Harvest Watermelon

Nothing is more refreshing than a slice of freshly picked juicy watermelon on a hot summer day. It tastes even better when the fruit is one that you have grown yourself. If you like growing your own watermelons but have no idea when to pick these delicious fruits, this handy guide will explain everything you need to know.

1 When to harvest watermelon
These juicy fruits are a popular summer treat.  

What are Watermelons?

A sprawling plant, the watermelon belongs to the Cucurbitaceae plant family alongside other common garden plants such as pumpkin, cucumber, spaghetti squash and both summer and winter squash. The varieties that you grow in your garden are almost certainly a cultivar of the Citrillus lunatus variety.

These plants are believed to have originated around 5,000 years ago in the Kalahari Desert. The seeds were first introduced to the United States by enslaved Africans. Today, thanks to hybridizing, there are over 100 varieties of watermelon in various shapes, sizes and colors.

An annual vining plant that produces large, lobed leaves with a distinctive hairy or coarse texture, yellow flowers emerge during the mid to late summer. Following pollination, the flowers fade to be replaced by fruits. A healthy plant can produce between two and four fruits.

2 Watermelon fruits
Each plant can produce up to 4 fruits. 

Modern cultivars are typically placed into one of four groups:

  • Icebox melons, weighing 5 to 15 pounds these are family-sized fruits
  • Picnic melons are large fruits weighing 15 to 50 pounds
  • Yellow or orange flesh melons tend to be sweeter than the pink or red-fleshed varieties,
  • Seedless melons, weighing 10 to 20 pounds, are self-sterile hybrids.

Suppose you want to explore the different types of watermelon plants that are suitable for growing in your garden. In that case, our guide highlights some of the more interesting cultivars currently available.

How to Grow and Care for Watermelon Plants

Before you learn when to harvest watermelon fruits, you must first know how to grow them.

While you can buy transplants, most varieties of squash plants are easy to grow from seed. These can be directly into the garden as soon as the soil temperature exceeds 70 ℉, usually around the same time as when peonies start to flower. Growers in colder regions can start their seeds in pots undercover 2 to 4 weeks before the last frost date.

If you have started the seedlings undercover, harden the young plants off before transplanting them into the garden.

These plants grow best in a full sun position. Exposure to sunlight encourages sugars to develop in the fruits, making them sweeter. While many varieties can tolerate partial shade, particularly in hot climates, too much shade impacts on the size and number of fruit that you can harvest.

3 Grow watermelon in full sun
These plants do best in a sunny spot.

Watermelons grow best in rich, well-draining soil. Ideally, it should be mildly acidic or neutral. Before sowing, the seeds work in lots of organic matter. This helps to sustain your plants growth and fruit development.

These plants like hot conditions, ideally 80 ℉ and warmer. They also do well in humid and arid conditions, as long as you remember to water them regularly.

Seeds and transplants are best planted in soil that has been mounded up. This encourages excess moisture to drain away, preventing rot. Mounding the soil also helps the roots to grow deeply.

Sow 4 to 5 seeds in the center of the mound, around 1 inch deep. After germination, thin the seeds out to 2 to 3 per mound. If you are transplanting seeds started undercover, plant 2 per mound.

Space your plants 4 to 6 ft apart. This generous spacing gives your growing plants plenty of room to spread and develop.

4 Space watermelons out
Give your plants room to grow.

Growers in cooler climates can use row covers to keep their young plants warm. Garden Expert Plant Covers not only help keep young plants warm in the spring and fall but also protect your plants from pests such as cucumber beetles.

Remove the floating row covers when flowers start to form on the plants. If pollinators can’t access your flowers, you won’t have any juicy fruits to harvest.

Gardeners in short seasons should prune away flowers that form later in the season, 6 to 7 weeks before the first predicted frost date of fall. This encourages the fruit already on the plant to ripen for you to harvest. If necessary, you can use row covers to shelter the plants from early fall frosts as the fruits ripen.

5 Watermelons develop on the ground
Fruits develop on the ground.  

As the fruits grow, carefully lift them onto a piece of cardboard. Alternatively, use a layer of straw or even an old carpet. Lifting the fruits off the ground protects them from pests and rotting in wet soil.

Weed the soil around the plants regularly.

Water your plant regularly until fruits start to form. At this stage, cease watering unless your garden is experiencing a dry spell. Healthy plants have deep roots and can withstand a short period of drought. However, too much water as the fruits develop causes them to lose sweetness.

These are heavy-feeding plants. Amend the soil before planting with organic matter to help sustain their growth. Alternatively, add a slow-release organic fertilizer such as Burpee Natural Organic Purpose Granular Fertilizer to the soil at the start of the season. Finally, side-dress the plants with a layer of compost around halfway through the season to sustain healthy growth.

Cucumber beetles are a common pest. Row covers can be used to prevent pests from attacking and destroying your plants. Vine borers, aphids and mites can also target the plants.

Powdery mildew can be an unsightly issue. But, as our guide to treating powdery mildew explains, watering the soil around the plant, keeping the leaves dry and correctly spacing the plants out so that air can freely circulate between the plants helps to prevent the disease.

For more detailed growing information, our guide to growing watermelons is suitable for everyone, from beginners to experienced gardeners.

Most varieties take 80 to 90 days to mature from seed. Short-season types are a little quicker, usually ready for harvest around 70 days after germination.

6 Watermelon fruit forms

Following pollination, fruits form in place of flowers.  

When to Harvest Watermelon

Growing squash plants is a fun task that is ideal for novices and children, but planting and caring for the plants is only one part of the task. The most challenging part for many people is knowing when to harvest watermelon fruits.

When you plant and your growing conditions both affect how long it takes for plants to mature. When to harvest watermelon also depends on what variety you are growing.

If you are growing from seed, most varieties are ready for harvest after around 80 days. However, different varieties can have variations, so check your seed packet for an exact timeframe.

From day 75, check your fruits daily to see how they ripen. You must be patient while the fruit ripens. Harvesting too soon means that your fruits won’t be as sweet or juicy as you may like.


Signs That it is Time to Harvest Watermelon

When you harvest, watermelon depends on the ripeness of the fruit. It takes a little experience to judge this. As the fruits develop, look out for changes in color, firmness and shape.

The curly tendrils that have developed on the vine close to where it attaches to the melon turn brown as the fruit ripens.

The color of the fruit tells you a lot about its ripeness and when to harvest. A dull, heavy fruit is almost certainly ripe. Shiny fruits are still ripening. The shape of ripe fruit is typically symmetrical and has no irregular bumps or dents.

7 Watermelon fruits
Fruits dullen as they ripen.  

Irregularly shaped fruit can be an indication that the fruit didn’t receive enough water when it was growing. Irregular-shaped fruit can also be a sign that the flower was not properly pollinated. Finally, large dents and cuts can signify fungal or insect infestation.

Dry weathering spots and vein-like webbing on the surface of the fruit are caused by excess sugar seeping from the fruit as it develops. These are signs that your fruit may be extra sweet.

Watermelon fruits form on the ground. The point where the fruit contacts the ground is known as the grow or field spot. As the fruit ripens, this changes color and provides a good indication of when you can harvest the fruit.

As the fruit develops, the grow spot is usually green or white. During ripening, the grow spot changes in color to a creamy or pale yellow color. This change indicates that the fruit is sweetening. If you harvest your fruit when the grow spot is still white or green, the fruit will be lacking in flavor.

The weight of the fruit tells you if it is time to harvest. Ideally, the fruit should feel heavy for its size. In general, the heavier the fruit, the juicier and more full of water it is.

How the fruit feels also tells you when to harvest watermelon. If you think the fruit is ripe, attempt to scratch the rind with your fingernail. You should not be able to break or pierce the skin.

Hold the fruit in both hands and squeeze it gently. A ripe fruit is firm and won’t yield easily under pressure. On the other hand, soft fruits are probably overripe.

8 Ripe watermelons are firm

Ripe fruits feel firm when squeezed.

Another test that can tell you when to harvest is to tap or slap the fruit. A ripe fruit sounds deep. A high-pitched sound suggests the fruit is underripe. Meanwhile, hollow-sounding fruits are overripe.

Finally, as the fruits ripen, they emit a sweet fragrance that you may be able to smell.

It can take a little practice before you become confident in knowing when to harvest watermelon.

However, once you can identify a ripe fruit, the next step is learning how to harvest watermelon.

How to Harvest Your Watermelon

Now that you know when to harvest watermelon fruits, the next step is learning how to harvest.

Use a sharp knife to cut the fruits away from the plant. You can also use heavy-duty garden shears or garden scissors to sever the vine that attaches the fruit to the plant. Aim to cut away around 2 inches of stem with the fruit.

Best eaten fresh, a whole fruit can be stored at room temperature for around a week. While you can store the fruits in a refrigerator, they keep better in a cool room; a temperature of 45 to 50 ℉ is ideal. In cool conditions, whole fruits keep for up to 2 weeks.

Cut slices can be kept fresh in the refrigerator for a few days.

9 Watermelon slices

Slices keep fresh for a few days.  

Fun and easy to grow, learning how and when to harvest watermelon fruits can be a tricky skill to master. But with a bit of practice, you will soon perfect the art, enabling you to enjoy sweet, juicy watermelons throughout the summer months.

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