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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>Gayle</span> Wed, 08/02/2017 - 20:32
Diatomaceous earth is the best! It is a natural silica rock that is ground into a fine powder. It is non toxic to humans or pets. You can sprinkle it right on the base of the plant or around the plant. Bugs have to walk on it to kill them and don't let it get wet, it is not effective when it is wet. You can also spray pests with soapy water, but it is more labor intensive.
<span>Beachmom3798</span> Fri, 07/28/2017 - 17:03
Hi guys. I've been using salt around my plants to keep out pest. I also make one a bucket full of water with a cup or so of peroxide. That gives the roots strength and it keep s the pest away as well. I don't know if it helps but I also sprinkle the mix lightly on the leaves. To prevent leaf disease. I also make a reason mix for them with coffee, tea, and banana peels lol. They love it. Finger crossed for this year's crop!
<span>Karra N Ansley</span> Tue, 04/11/2017 - 00:54
Last year I had a patch of watermelon. It did not do well because it didn't get watered. This year, the area where the watermelon grew is thick with plants that look like watermelon plants but I did not think they regrew. I know we did not have much of a winter so I was wondering if it is possible that these are watermelon plants--or, just weeds that look like watermelon. Any advice?
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 04/11/2017 - 09:49

These are weeds.  Watermelons' biggest issue is actually weed control and it's important to pull the weeds so that your watermelon is not forced to compete for necessary water and nutrients. Perennial grasses that grow in the watermelon patch can be difficult to control so you need to stay on top of them.  Before you plant, dig up all weeds with a hoe. You can't do this later or you'll damage the vines of the melon. Also, put mulch between the plants to keep the weeds down. Finally, plant multiple melons far apart so you can get between the plants to weed easily.

 <span>Hamza Jibril Bindawa</span> Mon, 03/13/2017 - 02:21
In his name the most high. I am very grateful with your writing and I find it very useful not to only me, but to all nation. But my only problem is where can I get such hybrid seed in Nigeria. God bless u
<span>Winhan</span> Mon, 02/27/2017 - 12:11
now my watermelon is a bigger stems,when i cut a weeks
<span>Metonu Gabriel</span> Sun, 04/22/2018 - 08:35
pls send me the details on how to plant water melon
<span>Phil</span> Wed, 02/08/2017 - 07:49
I sprayed malasol on my watermelon garden 10days ago, because there were flies, ants, works and other insects on the leaves and fruit and some watermelon began to rot. Now I want to know if it is safe to eat those that are ripe and others still growing?
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 02/10/2017 - 13:14

We would recommend that you contact the manufacturer of Malasol. If you still have the container, check the directions--it may have a number that you can call. Malasol is made by Efekto, which is based in South Africa.
You can find more information about Malasol here: http://www.efekto.co.za/shop/protection/garden-protection/garden-protection-insecticides/malasol/
Contact info here: http://www.efekto.co.za/contact/
Good luck!

 <span>Yourgolole</span> Wed, 01/25/2017 - 15:05
i am growing my watermelon inside and i want FRUIT but i also dont want bees flying everywhere so can you tell me how to pollinate it your self?