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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>Ter</span> Sun, 10/22/2017 - 05:10
Dry season produces the best tasting fruit so I'd advice you plant Oct/Nov. There are several varieties we are planting Erato F1 (eastwestseeds). Make ridges or heeps to help with water conservation and avoid over head watering. If one must water overhead be sure to water very early in the morning so plant can dry before temperature rises to produce humid conditions. Humidity brings fungal issues. Hope this help. Happy growing :-)
<span>Onyi Obinna</span> Sun, 04/29/2018 - 10:31
Watermelon don't come out in dry season
<span>Johnny A</span> Thu, 08/10/2017 - 18:16
What if the criteria for harvesting a watermelon are contradictory? I have a melon that sounds very hollow but the stem is still very green. Pick or wait? This is the first year my melons have gotten this far (escaped the groundhog, the vine borer, the drought...). I'm in Maryland.
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 08/11/2017 - 16:29

Hi Johnny, 

Sometimes it's a hard game to know if a watermelon is ripe. The things to look out for are these: The stem turns brown, the tendril on the stem turns brown, the spot on the bottom of the watermelon turns yellow, and the watermelon sounds hollow. Since you have the hollow sound, it is probably close, but still a tough judgment call. 

 <span>Aparna</span> Thu, 08/10/2017 - 11:01
Unlike regular watermelon - The Moon Star variety does not have stripes. How do I know when to harvest them... They say the sizes vary so I am not too sure to just go by size !!. I will watch out for that creamy patch. I am not sure I am good at hearing the difference in the thumping - they all sound the same to me !! TIA
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 08/10/2017 - 15:29

Hi Aparna,

To harvest the 'Moon & Stars' watermelon, wait until the stem has wilted and turned brown. Turn the watermelon over and examine the yellow spot on its underside: If the spot is pale yellow or white, leave it be for a few days before checking again; if the spot is bright yellow, the watermelon is ripe. We hope this helps!

 <span>Salman Alawadhi</span> Thu, 08/10/2017 - 07:52
Around 2 weeks ago I planted around 50 seeds all together in a small area and now at least 20-30 sprouted so do I need to transfer or separate them from each other? Please help me As Soon As Possible.
<span>Lori</span> Tue, 08/01/2017 - 13:27
My watermelons are growing good but here in Arizona things are opposite ,bring plants in during summer and put them out during winter, from anywhere else where I've lived. I've killed several before I learned what they like. I'm not having any luck with my melons and wondering if I take some off the vines off will it kill the plant? If not how would I do this ?
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 08/04/2017 - 14:42

Hi Lori,

If it's the heat that is causing you problems, try mulching the base of the vine (straw or bark mulch work well) to protect the plant from the burning sun and to better retain water. As to your question, if you are asking if it is helpful to take off some of the developing melons, the answer is yes, it can be helpful. Having to provide energy for fewer developing fruit can help to make the remaining melons to be bigger and healthier. If you are asking if it is helpful to cut off vines, the answer is not usually. Melon plants have about one female flower for every seven male flowers, meaning that if you start cutting off vines you may end up with no fruit. Cutting vines also can cause the plant to send out runners (smaller vines) to make up for the cut vines, which causes the plant to spend more energy growing runners than it does creating fruit. Either way, you will have a stronger plant if you let the vines be. We hope this helps!

 <span>Abdulfatah</span> Thu, 07/06/2017 - 09:34
I planted watermelon last two weeks,it started germinating this weeks pls advice me what can I do to make it save from pests