How to Grow Watermelon From Seed to Juicy Fruit

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This article is part of our Growing Fruit From Seed series.

Watermelons are one of the most delicious warm-weather crops for your food forest garden. Watermelons produce mouth-watering fruit, are tremendously sweet, and almost everyone loves eating them. We can show you how to grow watermelons from seed to harvest – and it’s surprisingly easy. We’ll also share how to germinate seeds, care for, and harvest melons.

My daughter holding a huge homegrown watermelon

How to Easily Grow Watermelon

Watermelons grow best in regions with warm temperatures between 65 and 95 degrees Fahrenheit. Watermelons also require a lengthy growing season – many watermelon cultivars take two to three months to mature. Luckily, homesteaders in cooler climates can grow watermelons if they germinate the seeds indoors. We will share our easy 6-step watermelon seed germination process below.

Growing Watermelons From Seed In 6 Easy Steps

Growing Watermelon Plant Time Lapse - Seed to Fruit (110 Days)

Remember that watermelon is a crop that demands hot weather and a long growing season. You can help lengthen your growing season by germinating watermelon seeds inside your kitchen. Here’s our easy, 6-step process to help you start.

Watermelon Growing Supplies Needed:

  • 12 fresh, healthy watermelon seeds
  • 12 biodegradable growing cups. (So you can directly sow the seedlings in the garden.)
  • A well-draining, sandy loam soil or potting mix
  • A warm, sunlit spot in your home
  • Fresh organic manure compost or a 5-10-10 fertilizer

You might also need a small heating pad to help germinate your watermelon seeds and nurture your plant as it develops. But a heating pad is only necessary if your room temperature dips below 70 degrees Fahrenheit.

1. Add Organic Fertilizer 60 Days Before Planting

Watermelons are tremendously heavy feeders. Way more than other fruit crops you may have grown before. But – feeding them is easy. Add an inch and a half or two of compost, aged cow manure, or a 5-10-10 fertilizer around your transplant site. Ensure the transplant site of your choosing gets at least six to eight hours of direct sunlight daily.

2. Starting Your Watermelon Seeds Indoors

Starting Watermelon Seeds Indoors

You can grow watermelons from seeds and sow them directly in your garden when the soil reaches at least 65 degrees Fahrenheit. For better results – wait for the soil to warm to 70 to 90 degrees Fahrenheit.

But – we usually recommend sowing the melon seeds indoors a month to six weeks before your final frost, as it can help lengthen your growing season, which is critical since watermelons require a long and warm growing season.

Thankfully – germinating watermelon seeds indoors is a piece of cake. Gather a few peat-growing cups and fill them with a well-draining potting mix. Dig a hole around one to one and a half inches deep. Insert your watermelon seeds in each hole. Then, give the seeds a splash of warm water.

Keep your watermelon seeds warm – at least 70 degrees Fahrenheit. Wait for your seeds to germinate over the next one to two weeks.

You can also buy baby watermelon plants from the store for an earlier harvest. But – starting from seeds is more entertaining – and can be cheaper.

3. Nurture Your Watermelon Seeds for 4 Weeks

Small watermelon seedling growing in cups indoors, starting seeds indoors

Your watermelon sprouting will grow surprisingly fast if you put the peat pots in a warm, sunny spot. Nurse and nurture them indoors until they grow to about 5 or 6 inches tall and have a few true leaves. This development will take around four weeks to six weeks.

During this time – keep your watermelon seedlings moist. Never let the soil get dry. Also, mind the temperatures. If the temperatures dip below 70 degrees Fahrenheit, consider using a heating mat to help keep the growing pot nice and warm. (A heat pad can also help germinate the seeds.)

4. Planting Your Watermelon Seedlings Outdoors

Watermelon seedling planted in the garden outdoors

Once your watermelon plant reaches five or six inches and has a few true leaves, it’s time to transplant it outdoors! Ensure the risk of frost has passed and the outdoor temperatures are above 70 degrees.

Also – the most significant issue when transplanting baby watermelon plants outdoors is their roots – they are tremendously sensitive. That’s why I recommend using biodegradable peat cups. That way, you can directly sow your tiny watermelon plants in the garden without disturbing or risking puncturing their sensitive roots.

Plant your baby watermelon plants in groups of two or three. Plant them with one to two feet between groups and six feet between rows.

Using biodegradable peat cups also makes the transplanting wickedly easy. Use your favorite garden shovel to dig a hole in the transplant site roughly 10% bigger than the peat cup. Then, insert the peat cup into the hole and cover any extra space with soil.

Watermelons take up a ton of space – so don’t crowd them! We will remove weak watermelons in a future step to help clear space – and give them room to flourish.

5. Add Mulch Around the Watermelon Transplants

Carefully add two to three inches of mulch around your baby watermelon transplants. Watermelon plants adore a thick layer of mulch around their vines. The mulch helps to suppress weeds, attain moisture, and maintain temperature. Mulch can also help feed the soil. 

Many gardeners swear that plastic mulch works excellently for watermelon vines. But we prefer using organic mulch – like coarse cedar chunks, redwood chips, or thick tree bark.

6. Removing Weak Watermelon Plants

Baby watermelon plant grown from seed growing in the warm and humid summer garden.

After transplanting the watermelon seeds and adding mulch, we then wait. Wait and watch them develop for a few weeks. We will then remove the weakest plants from each group. 

The idea is to leave only the most robust and promising watermelon plant from each group. We want to keep the healthiest and strongest plant – and cull the weak. We’ve found that this significantly increases our odds of producing healthy, mighty, and powerful watermelon plants with the best and juiciest yields.

(We also know that watermelon plants are tremendously sensitive – with somewhat fickle plant roots – and some transplants will perform better than others.)

If you live in a warm growing zone, you can germinate the watermelon seeds outdoors directly in your garden if the temperature exceeds 65 to 70 degrees Fahrenheit. When sowing outdoors, wait for your watermelon plants to reach at least five or six inches before adding mulch around the vine’s base! (We don’t want to smother or stifle the tiny plant.)

Related – 12 DIY Watermelon Trellis Ideas – Grow Watermelons Vertically!

Watermelon Plant Growing Requirements

Very healthy watermelon vine grown from seed with big ripe watermelon fruit

Watermelons are surprisingly easy to grow. They love growing in warm, sunny locations with well-drained, loose soil. Be careful when transplanting them, as the slightest injury can permanently stifle root growth.

Sunlight

Watermelons need lots of sunlight energy for the best fruit and flower production. Aim for at least six hours of direct sunlight – with eight to ten daily hours of sunlight being optimal. Watermelons also need a long growing season – some cultivars require up to three months. We always advise sowing watermelons indoors or acquiring a baby watermelon plant from a local plant nursery or garden center if in doubt!

Soil + Fertilizer

Watermelon gardens benefit from a well-draining, sandy, loamy soil with a pH of around 6 to 7.5. Watermelon plants are surprisingly heavy feeders – especially compared to other garden crops like peppers, kale, and tomatoes.

We always treat our watermelon transplant site with aged manure compost or a 5-10-10 compost fertilizer a few weeks to a month before planting.

Don’t use a nitrogen-dominant fertilizer when growing watermelons. Doing so may result in fewer fruits and excess vine growth. We’ve had good luck with granular fertilizer. But – don’t let the fertilizer pellets touch the watermelon foliage, or it may burn the delicate leaves.

(One of the only things, aside from cool temperatures, that watermelons hate is waterlogged soil. Ensure your soil drains properly. And – try to avoid a transplant site with clay soils.)

Watering

Watermelon plants in the garden with drip irrigation
Drip irrigation is a great way to water your watermelon plants grown from seed

We were surprised to learn that watermelons have relatively shallow roots – most of them exist in the top twelve inches of soil. As a result – watermelon vines don’t need as much water as you might expect.

Watering your watermelon is most critical during the first two months of growing. During this time, always keep the soil around your plants moist – and aim for around one to two inches of water weekly. (If the weather gets hot, monitor the garden soil daily. Never let the garden soil get too dry.)

For the final month of growing, try to minimize the watering somewhat. Watermelons have superior flavor when you decrease the watering to slightly below two inches weekly. We bet you’ll find minimizing their watering during their final month of growing will result in sweeter, juicier, and tastier fruit. šŸ˜‰

Pollination

female and male watermelon flower in spring in a greenhouse with sanded soil
Female and male watermelon flowers

Watermelon vines develop female and male flowers. The male watermelon flowers emit markedly massive pollen grains. But those pollen grains must reach the female flower for a healthy harvest. Honeybees, bumblebees, squash bees, and native bees help ensure proper pollination.

We’ve read that one honeybee hive per acre will help your watermelons attain maximum flowering and fruit. (Few honeybees in your yard will invariably result in poor pollination and lackluster melon fruit.)

Harvesting

How to Grow Watermelons - Complete Growing Guide

The biggest trick to harvesting watermelons is that they ripen at different times. So – instead of reaping them according to your calendar or stopwatch, it’s best to monitor your watermelon garden – especially after 60 or 70 days. By then, you will likely notice that your yummy homegrown melons are nearing ripeness and are almost ready for harvest.

Look for the underside of the melon to turn a whiteish-cream color, which is the best indicator of melon ripeness. You’ll also notice that the pig’s tail (the curly plant tendril near the watermelon) begins to die and fade as the watermelon approaches harvestability.

Some of our gardening friends swear you can determine a watermelon’s ripeness by tapping it and listening for a deep sound. But, we find that monitoring the watermelon’s underbelly and waiting for the pig’s tail to fade are far superior and more reliable methods.

Related – How to Grow an Avocado From Seed In 5 Easy Steps

Watermelon Planting and Growing Schedule

Here are the critical dates all watermelon growers should know.

MonthDescription
AprilApril is the best time to germinate watermelon seeds indoors if you live in a cooler climate. Keep the soil temperature above 65 degrees – and place your growing pot in a bright spot. Just about the only thing that will prevent your watermelon seeds from germinating is cold soil! So – consider using a heating pad to help maintain warm soil. And – keep the soil moist during this time. When scouting for an outdoor transplant site, remember that watermelons are spacious and love to sprawl. Give at least around 15 to 25 feet per plant.
MayMay is usually the perfect time to transplant your baby watermelon seedlings outdoors. The risk of frost is often gone in late spring, and if you live in a warm growing zone, you can also plant seeds directly in the garden whenever the soil reaches 65 degrees Fahrenheit. Give your freshly planted watermelon plants lots of water after transplanting – about one to two inches. Add row covers or a thick black plastic mulch layer around your watermelon plant to lock in moisture and heat. (We prefer organic mulches – but many watermelon gardeners swear that black plastic mulch works perfectly for melon rows.)
JuneIf you transplanted your watermelon plants in April, you might be surprised by some ripe melon in your garden during June. Keep an eye on fruit development – and remember to watch for the pig’s tail (the tendril leaf closest to the melon). The fading and dying pigtail signals mature, ripe fruit. Your watermelons usually need ample water in June – so keep your eyes on your plant to ensure the soil never dries. And if the weather gets super hot – give them an extra drink.
JulyJuly is when your watermelon plants should start to produce yummy and delicious fruit. Depending on when you planted them, you might be harvesting delicious melon throughout the month. July might also be a great time to reduce how much water you feed your melons. We advise slightly shrinking the water level your melon gets around one month before harvest – so the timing will vary.
AugustEven watermelon cultivars with the lengthiest mature date will likely begin maturing sometime during late summer. Depending on when you planted them outdoors – August might be the best time for ripe watermelons! Monitor your garden for fruit growth, and check underneath your melons for a faded yellow spot – which can help indicate ripeness and melon maturity.
SeptemberMost of your homegrown watermelon should be ready to harvest by early September. In many growing climates, the temperatures start flirting with their first frost in September. So – plan for your watermelon garden to mature before this time!
Watermelon Planting and Growing Schedule

Remember that your watermelon cultivar might vary slightly according to its preferences. And your growing zone!

Choosing the Best Watermelon Varieties and Cultivars

Over 1,200 watermelon cultivars exist – making it tricky to find your perfect variety. But we want to help you decide! So – we’re showcasing our three favorite watermelon cultivars below.

Crimson Watermelon

Crimson watermelons are our favorite classic seeded varieties. They’re beautiful-looking fruits. A successful crop will bless you with yummy and tasty treats throughout the summer season.

  • Plant Size: One to three feet tall by eight feet wide
  • Maturity: 70 to 100 days
  • Fruit Weight: 20 to 25 pounds
  • USDA Hardiness Zone: 6 to 13
  • Seedless: No
  • Appearance: Crimson watermelons have a medium, striped rind and tiny brown seeds. The melon rind appears light green with darker green stripes. They are markedly delicious and juicy fruits with yellowish flesh.

Golden Midget Watermelon

Golden midget watermelons are perfect if you want a cute, adorable fruit crop that won’t be nearly as big as other watermelon cultivars. They’re easy to grow, delicious, and seedless – making them an excellent choice for yummy treats during hot summers. They’re also our top pick if you want to try watermelon in containers or raised beds.

  • Plant Size: One to two feet tall and up to ten feet wide
  • Maturity: 70 to 75 days
  • Fruit Weight: 2 to 4 pounds
  • USDA Hardiness Zone: 4 to 11
  • Seedless: Yes
  • Appearance: Golden midget watermelons are a miniature variety with yellow to orange rinds and light red to pinkish flesh.

Jubilee Watermelon

We saved our favorite watermelon flavor for last. The Jubilee watermelon! These heavy-hitting fruits have an oblong shape, deep red flesh, and classically green rinds. They’re not dainty icebox watermelons – as the fruits can reach over 40 pounds. (These uncut watermelon fruits are almost too large to carry!)

  • Plant Size: One and a half to two feet tall and up to ten feet wide
  • Maturity: 80 to 90 days
  • Fruit Weight: 30 to 40 pounds (They’re massive!)
  • USDA Hardiness Zone: 3 through 11
  • Seedless: No
  • Appearance: Jubilee watermelons are sizely oval-shaped fruits. They appear like classic melons with reddish and sugary, delicious flesh. Their rinds are usually light green, with dark green stripes.

This tiny list above barely scratches the surface of watermelon cultivars. We tried to choose our three favorites – including seeded and seedless varieties. But no matter which melon variety you like, do your homework. All watermelon varieties vary slightly.

Related – Here’s How to Grow a Lemon Tree From a Seed

Common Problems With Watermelon Plants

6 Watermelon Growing Mistakes To Avoid 🍉

Watermelons are surprisingly easy to grow if you offer ample warm sunlight, nutrient-rich soil that drains well, and plenty of loose soil for their delicate root systems.

But even if you give watermelons everything they need, the following watermelon ailments can find their way into your garden.

Gummy Stem Blight

Blight symptoms on watermelon leaf causal agent Didymella bryoniae .Gummy Stem blight.

Gummy stem blight is a nasty black rot that impacts watermelons, cucumbers, squash, and pumpkins. Didymella bryoniae, a fungal pathogen, causes gummy stem blight.

If you suspect gummy stem blight, the symptoms are similar to other fungal diseases. Look for stunted growth, circular spots on leaves, and oozy stem cankers. (Yuck!)

The best way to manage gummy stem blight is to choose watermelon plants free of plant diseases. In other words – never introduce tainted crops to your garden! Overly wet and cloudy weather and poor air circulation can also exacerbate symptoms.

We’ve read from several reliable sources that overhead drip irrigation can help didymella bryoniae flourish. (Overhead drip irrigation is BAD in this case.)

Management often involves using root-level drip irrigation instead of overhead. Never use overhead irrigation for watermelon crops. Watering from overhead soakers can contribute to overly wet foliage and soil moisture. Use a garden hose to wet the root level without soaking the melon leaves or vine.

You can also use an automated soaker hose to water your melon crops. But – ensure the water goes to the root level. Don’t soak the entire plant!

Downy Mildew

Pseudoperonospora cubensis on watermelon

Downy mildew, or Pseudoperonospora cubensis, is an icky powdery mildew that can impact watermelon plant health at any growth stage.

Like many melon ailments, symptoms are usually worse during cool and wet weather. Downy mildew symptoms include black or brown mildew on leaves. The mildew is most visible during the morning. Prolonged exposure leads to plant defoliation, wilting leaves, and leaf death.

Try increasing air circulation to help manage downy mildew. Using wide row spacing and watermelon trellis stations can help tremendously.

It’s also wise to remove dead plants with heavy infection – and clear any lingering debris with mildew remnants.

When all else fails – consider using a fungicide like chlorothalonil or mancozeb.

Insect Pests

Aphids and Ants at Top of Watermelon Leaves
Aphids on a watermelon leaf

We have bad news for watermelon growers. Insects love eating them almost as much as we do! Keep your eyes out for these pests that can wreak havoc upon your melon harvest.

Watermelon Insect Pests:

  • Aphids
  • Cucumber beetles (and larvae)
  • Leafminers
  • Seed corn maggots
  • Squash bugs
  • Squash vine borers
  • Two-spotted spider mites

We monitor our watermelon vines regularly and scan for pests. Whenever we find infestations – we manually pluck and remove them. Remove infected leaves and clear bad infestations.

If it’s impossible to pluck the insect pests – consider spraying them with the hose. I’ve yet to find an aphid infestation that a cold blast from the hose couldn’t fix!

You can also use organic pesticides around your watermelon crop if you must. We prefer insecticidal soap and natural organic pest control sprays – like hot pepper spray, cayenne pepper spray, and citrus oil.

We also have good news. Your melon garden usually has boatloads of predatory mites and insects that will help rid any common pest. We’re always paranoid that synthetic pesticides will injure and harm these beneficial predators! So – we only recommend using pesticides if the infestation gets out of hand.

How to grow watermelon from seed to harvest indoor and outdoor growing tips.

Related – How to Grow Pineberries for Abundant and Tasty Fruit

Conclusion

Thank you for reading our guide about growing watermelons from seed!

We grow melons every year as soon as the chance of frost passes. They’re one of our favorite ground-layer food forest crops. And they make one of the best BBQ sides to serve alongside fried chicken, smoked ribs, cheeseburgers, or veggie platters for our vegetarian friends. šŸ™‚

What about you?

  • What’s your favorite watermelon cultivar to grow?
  • Do you start your watermelon seeds inside? Or do you grow them outdoors?
  • Do you grow your watermelons in mounds? If so – how many melon seeds per mound do you sow?
  • What’s your favorite organic matter fertilizer to help dress plants?
  • Have your young watermelon plants ever had a late spring frost? Did your plants survive?

We can’t get enough of these yummy, juicy fruits.

And – we hope to hear from you if you grow some anytime soon.

Thanks again for reading.

Have a great day!

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