Humans have cultivated watermelon plants for thousands of years. Originally native to southwest Arica, watermelons now grow in hot climates worldwide.
Want to continue this juicy history by planting a patch of your own? Keep reading.
In this article, we’ll explain the watermelon growth stages in detail. Then we’ll offer some tips to ensure you have an abundant harvest.
8 Watermelon Growing Stages & Timeline
Over three months, a watermelon plant grows from a tiny seed into a large fruit. First, let’s go over a step-by-step breakdown of the watermelon growth process. That way, you’ll understand the timeline and events of the growing stages.
A single watermelon can weigh up to 25 lbs. But the growing cycle of watermelon begins with a tiny black and brown seed. This flat, teardrop-shaped seed is no bigger than half an inch long.
Before you put any seeds in the ground, you’ll need to select a variety. For example, there are over 1,000 varieties of watermelon, so the choice can be overwhelming.
Here are some things to consider when selecting a variety: seeded or seedless, red flesh or yellow flesh, size, shape, and flavor. But the plant’s growing season is arguably the most important consideration for first-time growers.
If you live in a region with shorter summers, you’ll probably want to select an early variety. Early-season watermelon varieties take 70-75 days to harvest (roughly two and a half months).
Popular Main Season Varieties
- Black Diamond Watermelon – red flesh, 30-50 lbs
- Charleston Gray – red flesh, 25-35 lbs
- Crimson Sweet – red flesh, 15-25 lbs
- Honey Heart – yellow flesh, 8-10 lbs
If you’re attempting to grow watermelon in colder climates, be prepared to plant in early spring. First, identify the day of the last spring freeze for your region. Then count back four weeks. This date is when you want to plant the seeds.
Start by planting the watermelon seeds indoors. When soil temperatures reach 70 F, transplant the seeds.
If you live in warmer climates with long sunny summers, you have more flexibility in your planting schedule. (The watermelon growth stages will remain the same, but the exact timeline may vary slightly.)
Plant the seeds in raised rows of loamy, well-drained soil. These hills help the soil drain properly while retaining the sun’s heat.
Keep a distance of 2-3 feet between each seed, and nestle each watermelon seed one inch below the soil. Maintain about six feet between each row. Water the seeds to begin germination.
2.) Germination & Sprouting
Seed germination begins once you’ve planted the seed in the soil. It then takes 3-14 days for the seed to complete germination.
During germination, the seed sprouts a tiny stem called a hypocotyl. This stem allows the plant to root in the soil. The seed embryo then develops radicles that eventually develop into the primary root.
(The fully developed root system will reach about six feet deep.)
Once the seed has germinated, it produces embryonic leaves called cotyledons. These two leaves will push through the soil surface.
The period of germination and sprouting is the most vulnerable of the watermelon seed growth stages. Protect your seedlings from cold weather and animals. Moisture is crucial during germination, but be careful not to overwater the seedlings.
3.) Vegetative Growth
After the seedlings have sprouted, plant growth accelerates.
In about 5-10 days, four or five leaves will replace the tiny embryonic leaves. This growth is known as the first set of true leaves.
True leaves are vegetative growth resembling mature watermelon plant leaves. They offer increased surface area, helping the plant to perform photosynthesis.
Photosynthesis is the process through which plants convert sunlight into energy. This energy fuels additional growth. And the more growth available, the more the plant can perform photosynthesis.
The leafage becomes longer and sturdier within two weeks. During this time, the plant also produces the main vine.
Once this runner vine has grown a foot long, additional foliage will begin to sprout along the vine.
Dark green leaves sprout along the vine every 3-5 inches. Spiky hairs cover both the leaves and the vines.
Approximately one month after you’ve planted the watermelon, you’ll see new vines develop from the main vine. Depending on the seed variety, the vines will eventually grow up to 10-12 feet long.
Branching allows a single watermelon plant to produce multiple melons. (Each branch can grow one watermelon.)
Healthy watermelon plants can support 3-5 branching vines. If your watermelon plant struggles to produce robust growth, remove weak and excess branches from the main vine.
This branching requires more nutrients and water. In addition, thinning the branches gives the plant the best chance of producing fruit.
The branching stage takes just over a month to complete.
5.) Flower Production & Pollination
Watermelon plants produce both male and female flowers. Each solitary yellow flower measures about 1-3 inches wide with 4-5 petals.
The male flower grows first, usually during the branching phase—the female flower forms at the tip of a mature vine branch.
Male flowers contain an anther covered in pollen. Female flowers have a stigma. Although these flowers allow the watermelon to pollinate, the male flower will wither after one day.
Watermelons cannot self-pollinate. They require assistance from pollinators such as bees, insects, or even humans. Pollination occurs when the male flower’s pollen contacts the female flower’s ova.
After flowering, when do watermelons begin to grow?
Once the plant has successfully pollinated, it begins to develop a marble-sized fruit within a few days. The female flower will eventually fall off as the fruit grows.
This moment might be the most exciting of all the watermelon growth stages. The marble-sized fruit will swell into a full-sized watermelon in less than a month.
6.) Setting Fruit
After pollination, a tiny bulge begins to form behind the female flower. This fruit will slowly swell over the course of a month into a watermelon.
Believe it or not, the fruit of a watermelon plant is technically a berry. A pepo, to be even more precise. It has a hard outer skin, known as a rind, and soft watery flesh.
The variety of the watermelon impacts the shape, size, flesh color, rind thickness, and flavor of the fruit.
For instance, a sugar baby watermelon is a spherical fruit. It has a dark green rind with no variegation. But a crimson sweet watermelon has a more oblong shape with light green and yellow stripes.
Variety also affects the time it takes a watermelon to mature. In general, smaller varieties mature more quickly than larger varieties.
As the fruit sets, seeds develop within the melon’s flesh.
Watermelons will reach full maturity about a month after initial fruiting. However, the exact timeline will vary depending on the watermelon variety and the weather.
Tap the melon at the end of the growing season to determine ripeness. Ripe watermelons will produce a hollow sound.
You can also rely on a few visual cues. For example, the area where the fruit touches the ground will have yellowed on a ripe watermelon. The tendrils on the vine might similarly have turned brown.
Once the fruit has fully ripened, it’s time to harvest the melon! Use a small pair of shears to snip the fruit off the vine.
After you have harvested the fruit, the watermelon vine will begin to dry. Sadly, this plant is an annual, which means it will die at the end of the season.
But it’s not all bad news. Depending on the variety you’ve planted, you might be able to collect mature seeds from the watermelon.
Let these seeds dry. You can then plant them next spring, starting the watermelon growth stages all over again.
Watermelon Growing Tips
Now you understand the growth stages of watermelon. Let’s go over a few quick tips to ensure growing success at each stage. That way, you’ll understand how to grow watermelon plants from seed to fruit.
- Growing Conditions: Before you start planting, check that your region offers ideal growing conditions for watermelon. This plant grows best in temperatures ranging from 65-95 F. Soil pH should be between 6.0-6.5 for best melon growth.
- Watering: The watering needs of watermelons vary depending on the stage of growth. Water is crucial to germination, so water the seed thoroughly after planting. As the plant produces vegetative growth and flowers, water the plant consistently so that the soil is moist but not soaked. But if you want the best-tasting melons, reduce watering once the fruit appears.
- Germination: Consider chitting the seeds before planting. This method forces seeds to germinate outside the soil, ensuring that you only plant viable seeds.
- Sprouting: Larger watermelon plants transplant poorly. Once the plant has formed a set of true leaves, transplant them outside.
- Vegetative Growth: As the plant develops additional foliage, prune yellow and dead leaves from the main vine. You can also remove weak or leggy side vines. This pruning helps the plant conserve energy.
- Pollination: Watermelon cannot self-pollinate. If your garden doesn’t host many pollinators, you might need to pollinate the flowers yourself. Use a cotton swab to transfer pollen from the male flower to the stigma on the female flower.
- Seedless Watermelon: The seedless watermelon is a sterile hybrid. You will need to plant regular watermelons along with seedless melons for pollination.
- Setting Fruit: Watermelon plants will benefit from well-balanced fertilizer while they produce vegetative growth. But once the fruit begins to grow, switch to a low-nitrogen fertilizer.
Still trying to understand watermelon growth stages? Take a look at these quick answers to some frequently asked questions.
How Long Does a Watermelon Take to Grow?
A watermelon takes roughly three months to grow from seed to fully mature fruit. The plant spends the first two months germinating, sprouting, vining, and flowering. A fruit develops after the flowers have been pollinated, taking about a month to reach full size.
What Is a Watermelon’s Lifespan?
Watermelon is an annual plant; it will only yield fruit for one season. From seed, watermelon plants take anywhere from 70-90 days to produce mature fruit. Once harvested, a watermelon will keep for two weeks in the fridge.