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How to Plant, Grow, and Harvest Watermelon

Image Credit:
Pixabay
Botanical Name
Citrullus lanatus
Grown as
Annual
Toxicity
Non-toxic
Sun Exposure
Full Sun
Water Needs
High
Height
1–3 feet
Spread
3-6 feet
Soil pH
Neutral
Bloom Time
Summer
Flower Color
Yellow
Special Features
Container-Friendly
Attracts Pollinators
Resilience
Heat-Tolerant
Plant Type
Fruit
Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

Watermelon is the ultimate summer treat—and growing your own makes it even sweeter! Whether you’re in a warm climate or working with a short season, this guide covers everything from planting to picking the perfect melon. Let’s get growing!

Because watermelons need a long period of warm weather to grow well, they tend to be more popular in warmer climates with long growing seasons. However, gardeners in colder climates can still successfully grow watermelons by starting seeds indoors or purchasing young plants from a nursery and growing shorter-season varieties. Depending on the variety of watermelon, it can take between 70 and 100 days to go from planting to harvest.

Planting

When to Plant Watermelons

  • In cool climates with short growing seasons, start seeds indoors 2 to 3 weeks before your last frost date. Plan to transplant seedlings into the garden about 2 weeks after that date or when the soil has warmed to at least 65°F (18°C).
  • In warmer climates with long growing seasons, sow seeds directly outdoors 1 to 2 weeks after your last frost date, as long as the soil temperature has warmed to at least 65°F (18°C).
  • Young watermelon plants can also be bought from nurseries. Plant these after there is no longer a chance of frost; they are very tender. Watch the local forecast and err on the side of caution! Consider laying black plastic over your planting area to warm the soil even more.
    • Tip: Starting with young plants can result in an earlier harvest (usually up to 2 weeks earlier), so consider buying young plants, particularly if you live in a cooler climate.

Choosing and Preparing a Planting Site

  • Amend soil with aged manure, seaweed, and/or compost before planting. Watermelons are heavy feeders, meaning they need soil that is fertile and has a high nutrient level. Learn more about soil amendments and preparing soil for planting.
  • Watermelons do best in loamy, somewhat sandy, well-drained soil. They can struggle in soil that contains too much clay and doesn’t drain well.
  • Watermelons prefer a soil pH between 6.0 and 7.5 (“slightly acidic to neutral”).
  • Watermelons need A LOT of space—up to 20 square feet per plant. Their vines need room to sprawl, so plant them in a place where they won’t crowd out other crops.
  • Growing the vines in raised rows, known as hills, ensures good drainage and will hold the sun’s heat longer.
    • Plan to space the plants 2-3 feet apart in a 5-foot-wide hill.
    • If you’re growing in traditional rows, space them at least 6 feet apart. 

watermelon growing in a garden

How to Plant Watermelons

  • Sow seeds 1/2 to 1 inch deep outdoors or 1/4 to 1/2 inch deep in seed-starting pots indoors.
    • Tip: To allow for more root growth, use larger starting pots than you would for most seeds. Also, consider using compostable pots that can be cut away or planted directly in the garden, as this will minimize the risk of damaging seedlings’ tender roots during transplanting.
  • If direct seeding outdoors, sow 4 to 6 seeds per hill, eventually thinning to 2 to 3 seedlings. 

Transplanting Seedlings

  • Handle watermelon seedlings with extreme care when you transplant. Their roots are very fragile, so try not to disturb the soil when removing them from pots.
  • After transplanting, cover the plants with row covers to keep pests at bay. Remember to remove the row covers when you see both male and female flowers on the vine, as pollinators will need to access the flowers.
  • Find even more tips for planting melons in your home garden.

Growing

Watering Watermelons

  • Watering is very important—from planting until fruit begins to form. While melon plants are growing, blooming, and setting fruit, they need 1 to 2 inches of water per week.
  • Keep soil moist but not waterlogged. Water at the vine’s base in the morning, and try to avoid wetting the leaves and avoid overhead watering. Reduce watering once fruit is growing. Dry weather produces the sweetest melon.

Fertilizing

  • If you choose to fertilize (and many do), make sure it delivers more nitrogen than phosphorus and potassium, as this will encourage leaf and vine growth. However, after flowering begins, use a fertilizer with less nitrogen to instead encourage flowers and fruit. We like to use a seaweed-based fertilizer.

Flowering and Fruiting

  • Vines produce male and female flowers separately on the same plant. They often begin producing male flowers several weeks before the females appear. Do not be concerned if the male flowers fall off. The female flowers (which have a swollen bulb at the base) will stay on the vine and bear fruit.
  • Blossoms require pollination to set fruit, so be kind to the bees!
  • As the fruit is ripening, prevent rotting by gently lifting it and putting cardboard or straw between the fruit and the soil.

Baby watermelon

General Watermelon Care Tips

  • Mulching with black plastic or straw around the plants will serve multiple purposes: it will warm the soil, hinder weed growth, and keep developing fruits off the soil.
  • Pruning generally isn’t necessary for watermelon plants, but vine productivity may be improved if you do not allow lateral (side) vines to grow and stick to the main vine. When the plant is young, just cut off the end buds as they form (before the side shoots become vines). You can also pinch off some blossoms to focus the energy on fewer melons (though it’s challenging to kill off a potential fruit).

Harvesting

Watermelons don’t continue ripening after they are picked, so harvest time is important. They generally ripen over a two-week period, so keep your eye on them.

How to Tell If a Watermelon Is Ripe

Dr. Bill Rhodes, professor of horticulture at Clemson University, offers the following advice on how to tell when watermelons are ripe:

  • Thump it. If the watermelon sounds hollow, it’s ripe.
  • Look at the color on the top. The watermelon is ripe when there is little contrast between the stripes.
  • Look at the color on the bottom. An immature watermelon will have a white bottom; a ripe melon will have a cream- or yellow-colored bottom.
  • Press on it. If the watermelon sounds like it gives a little, it’s ripe. (Note: Rhodes doesn’t like this method because it can ruin the quality of the fruit.)
  • Check the tendril. If it’s green, wait. If it’s half-dead, the watermelon is nearly ripe or ripe. If the tendril is fully dead, it’s ripe or overripe; it’s not going to get any riper, so you might as well pick!
  • Stems should be cut with a sharp knife close to the fruit.

Check out these tips for more ways to tell if a watermelon is ripe.

How to Store Watermelons

  • Watermelons can be stored uncut for about 10 days. If cut, they can last in the refrigerator for about 4 days. Wrap tightly in plastic.

Pests and Problems

Types

  • ‘Golden Midget’: 70 days to maturity. Bears petite, yellow-skinned, 3-pound melons with pink flesh. Good for northern gardeners.
  • ‘Sugar Baby’: 80 days to maturity. Produces 10-pound melons with bright red flesh. This variety of smaller fruit can be planted just 4 feet apart.
  • ‘Sweet Beauty’: 80 days to maturity. A 2004 All-America Selection. Bears 6-pound, oblong melons with red flesh.

Wit and Wisdom

  • What’s in a name? Watermelons are 90 percent water.
  • The pumpkin vine never bears watermelons.
  • August 3 is National Watermelon Day (U.S.)!

Fruit

About The Author

Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website, and is also a certified master gardener in the state of Indiana.

Read more from Catherine Boeckmann

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Comments

<span>Joe Henthorn</span> Thu, 06/12/2014 - 10:50
I have a 20 X 20 raised bed melon patch to ensure perfect soil conditions, a tilled combination of top soil, compost and sand. Using mounds about 24 inches in diameter,and 4 feet apart, I plant a circle of 6 seeds around the center of each mound. My question is how many plants should I leave (thinning) once they are up and I have established the stronger ones. Should I leave all 6, thin the mound to only 2 to 3 plants per mound, or leave just one? Thank you
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 06/13/2014 - 11:01

Sounds like a perfect setup for your watermelons! Once the seedlings emerge and you've determined which are the stronger ones, you can thin to 2 or 3 vigorous plants per mound. Happy gardening!

 <span>Rachell</span> Tue, 05/05/2015 - 13:15
Of course it is it's amazing
<span>Jeremy Becker</span> Mon, 06/09/2014 - 06:41

I have two different varieties of watermelon and certain plants are growing faster than other plants. I was considering hybridizing them, so my question is this: will the plants continually produce male and female flowers throughout the growing season or does each plant need to be roughly the same age so that they flower at same time? Also, some of the same plant variety are emerging from the soil about 4 to 6 days after their brothers and sisters. I'm new to growing watermelons, but who doesn't love a couple slices of watermelon during the summer. Thank you for your assistance. :-)

<a title="View user profile." href="/author/editors">The Editors</a> Tue, 06/10/2014 - 05:18

Watermelons have separate male and female flowers on the SAME plant so they don't need another plant to pollinate. What they need are the pollinators—the bees. Watermelons do cross-pollinate with other watermelon varities. If you do decide to encourage cross-pollination, then I imagine you would want flowers opening around the same time. The female watermelon flowers do not open for very long and this is a morning event. You can always hand pollinate by plucking off a healthy male flower, removing its petals, and wiping the pollen on its stamen on to the center of the female flower. Note that you will not have a hybrid in this first generation. You need to save the seeds from the crossed melon and plant them next season to see what you get!

 <span>Ptg</span> Sun, 06/08/2014 - 17:10
My watermelons are developing both male and female flowers, but the plants are still quite small. Should I pinch off the flowers to let the vines develop more, or is it fine for them to put out flowers despite being fairly small? (I would say square foot large plants.) I grew watermelon last year and the vines were huge and sprawling, so I'm a little concerned despite the vines otherwise looking very healthy.
<span>Electriccow12</span> Sat, 05/31/2014 - 09:19
I'm going to be planting watermelon next year and I want to make sure everything is perfect so I can have an excellent and successful harvest. :) Using a tool provided by our local university I have found the watermelon seeds recommended for my area. However since I have never grown a watermelon before I don't know which of these watermelons are the sweetest. Charleston Gray Crimson Sweet Dixielee Jubilee Tendersweet (Orange) The only one I think is sweet (based off a youtube video I saw of this harvest) is the Jubilee watermelon. Any thoughts/help on this? Thank you :)
<span>Wilber50050</span> Mon, 06/16/2014 - 12:58
The tendersweet orange is the sweetest with crimson sweet after that.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 06/03/2014 - 09:57

I don't know every variety but there are some very sweet watermelons on your list (Crimson Sweet, Jubilee) based on this reference chart which lists the "Brix" sweetness level: 

http://agsyst.wsu.edu/watermelonphotos.html

 <span>Charlie2</span> Thu, 05/22/2014 - 15:47
I have probably 10 water melon plants growing in a 30 gallon container, can i just let them spill from the container and ramble on the ground?