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Botanical Name
Citrullus lanatus
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Planting, Growing, and Harvesting Watermelons
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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.
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! Learn how to support pollinators in your garden.
- As the fruit is ripening, prevent rotting by gently lifting it and putting cardboard or straw between the fruit and the soil.
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).
Types
- ‘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.
- ‘Golden Midget’: 70 days to maturity. Bears petite, yellow-skinned 3-pound melons with pink flesh. Good for Northern gardeners.
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Comments
My watermelons never seem to ripen. I keep checking them but no ripe melons. I have had actual melons growing for 4 months. Cut them open and still not rip. This happens every year. What am I not doing? Can't seem to grow radishes either. Thanks.
We can only suspect the weather conditions. Melons need heat to ripen properly. Cool cloudy weather in the spring will slow down thier development. Also, have you used plenty of fertilizer and water? Watermelon plants are heavy feeders.
You provide spectacular information on this website. Thank you for your help!
How many melons can be harvest from a single vine. This is my first time gardening watermelons. I have followed every step one by one. I lived in Puerto Rico and the temperature is aroumd 90 degrees all year around.
There are lots of opinions about how many watermelons to expect—or let grow—on one vine. Consider that if several fruits get started, it might be to your benefit to remove the weakest or smallest ones, so that a few do very well. Of course, in your environment, many may do very well. Watch your plants and decide as they appear and grow.
I have a lot of watermelons, some that are older than others are smaller than the newer ones? And I can't figure out when they will be ready to harvest? They have been growing for a couple months now and they are still white on the bottom?
Water melon do not slip from the vine or give off an odor to indicate they they are ripe. People use all kinds of methods: First, check your seed packet for the number of days to maturity, consider when you planted these and count the days since then. Some say that a "waxy" rind means a watermelon is ripe. The "thump" test involves knocking on the rind with a knuckle and listening for a dull, muffled sound. (Some say a watermelon always sounds dull and muffled when rapped that way.) White colr means only that that side was away from the sun.
When you harvest your melon, cut it from the stem, do not pull it, and do it in the morning.
My volunteer melon was growing well, until placed on a flat brick. It grew for a.couple of days, then stopped. I checked the bottom and it had split. What happened?
Oh, so sorry to hear. Typically excessive watering or heavy rain will cause a ripening watermelon to split.
The rule of thumb is water less as the melon is ripening; this improves flavor.
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Sweet Baby Watermelon has district stripes when immature and become almost black when ripe. A Bush Sugar Baby has a dark green rind with no stripes.