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Watermelons are planted in late spring or early summer, once the soil has warmed to at least 70°F and all danger of frost has passed.
If you’ve been wondering how and when to plant watermelon, the short answer is simple: give them heat, give them sun, and give them room to sprawl.
Watermelon is a warm-season crop that absolutely hates the cold, so timing your planting right is everything.
Plant too early and the seeds rot in cool, damp soil.
Plant too late and you may not get ripe fruit before the season ends.
In this post, we’ll walk through exactly how and when to plant watermelon so you can grow sweet, juicy fruit right in your own backyard.
Let’s dig in.
When to Plant Watermelon
Knowing when to plant watermelon is the difference between a thriving vine and a sad, stunted seedling.
Here’s how to nail the timing.
1. Wait Until the Soil Warms Up
Watermelon seeds need soil temperatures of at least 70°F to germinate, and they truly thrive once the soil hits 80°F.
If you plant too early in cold soil, the seeds will just sit there and rot.
A good rule of thumb is to wait at least two weeks after your last expected frost date.
You can grab an inexpensive soil thermometer to check, or just wait until the weather has been consistently warm for a couple of weeks.
2. Follow Your Growing Zone
When to plant watermelon depends a lot on where you live.
In warmer southern regions, you can usually plant watermelon from late March through May.
In cooler northern zones, you’ll want to wait until late May or even mid-June.
If you’re starting seeds indoors, begin them about three to four weeks before your last frost date.
Just don’t rush them outside until the nights stay above 50°F.
3. Watch the Nighttime Temperatures
Watermelon plants are sensitive to cold, and nighttime temps below 50°F can stunt their growth.
So even if your days are warm, check that your nights are consistently mild before you plant watermelon in the garden.
A late cold snap can set your plants back by weeks.
How to Plant Watermelon
Now that you know when to plant watermelon, let’s talk about how to do it right.
Getting the planting method down gives your vines the best possible start.
1. Pick the Right Spot
Watermelons need full sun, at least six to eight hours a day, and plenty of space.
Choose a spot with loose, well-draining soil rich in organic matter.
Since watermelon vines sprawl, give each plant about 3 to 5 feet of room in every direction.
If space is tight, you can grow watermelon vertically on a sturdy trellis, but you’ll need to support the heavy fruit with slings.
2. Prepare the Soil
Before you plant watermelon, amend the soil with compost or aged manure to boost fertility.
Watermelons love slightly acidic soil with a pH between 6.0 and 6.8.
You can also build small mounds or hills about 6 inches tall, which helps the soil warm up faster and improves drainage.
This is especially helpful in cooler climates where soil stays cold longer.
3. Plant the Seeds or Seedlings
To plant watermelon from seed, sow three to four seeds about 1 inch deep in each hill.
Space your hills 4 to 6 feet apart.
Once the seedlings sprout and develop a few leaves, thin them down to the two strongest plants per hill.
If you’re transplanting seedlings, set them out carefully without disturbing the roots, and water them in well.
You can also plant watermelon in rows, but hills tend to work better for vining varieties.
4. Water and Mulch
After you plant watermelon, give them a deep watering to settle the soil.
Then add a layer of mulch to retain moisture and keep weeds down.
Watermelons need about 1 to 2 inches of water per week, especially while the fruit is developing.
Just avoid getting the leaves wet, since that can invite disease.
Drip irrigation or soaker hoses are ideal here.
5. Feed Them Well
Watermelons are heavy feeders, so once the vines start running, give them a side dressing of balanced fertilizer.
Too much nitrogen will give you tons of leaves and no fruit, so look for a blend that’s lower in nitrogen and higher in phosphorus and potassium.
This helps the plant focus its energy on producing sweet, ripe melons.
Tips for Growing Watermelon Successfully
Once you’ve figured out how and when to plant watermelon, a few extra tips can make a big difference.
Keep the vines weed-free early on, but once they spread, the leaves will shade out most weeds on their own.
Be patient with harvesting too.
A watermelon is ripe when the tendril near the fruit turns brown and dry, the underside turns creamy yellow, and it makes a deep, hollow thump when you knock on it.
And if you’re growing in a short-season climate, choose a variety with fewer days to maturity, like ‘Sugar Baby’ or ‘Blacktail Mountain.’
These smaller types ripen faster and still taste amazing.
So, How and When to Plant Watermelon?
To plant watermelon, wait until the soil is warm and all frost danger has passed, then give them full sun, rich soil, and plenty of space to sprawl.
When to plant watermelon really comes down to warmth, so timing it right after the last frost in your zone sets you up for success.
Follow these steps and you’ll be rewarded with vines full of sweet, homegrown watermelon by the end of summer.