How to Grow Watermelons: Guide With Detailed Instructions

Most people love watermelon, but it’s hit or miss to bring home a ripe sweet melon when you buy them at the grocery store. The good news is that it’s incredibly straightforward to grow watermelon plants.

With careful planning, proper care, and the right growing conditions, you can grow and harvest your very own sweet watermelons.

Besides being sweet and juicy, watermelons are super nutritious. At the end of this article, we share some nutrition facts about watermelon and unique recipe ideas for making the most of your watermelon harvest.

Preparation and planning is the key to an abundant watermelon harvest.

When to Plant Watermelons

Depending on the watermelon cultivar you grow, you need to know the number of days it will take for your plants to reach maturity.

This number is essential because you will need to choose cultivars that work with your growing season.

Also, you need to know whether to start seedlings inside or sow seeds directly into the ground. Watermelon plants thrive best when the seeds are sown directly into the ground because the roots of watermelon plants are somewhat sensitive.

Nevertheless, direct sowing doesn’t work in every climate or watermelon variety.

Watermelon Plant Varieties

There are three types of watermelons:

  • Early watermelons (70-75 days to harvest)
  • Main season watermelons (80-85 days to harvest)
  • Seedless watermelons (80-85 days to harvest)

The watermelon varieties you grow will depend on your growing season and your USDA Hardiness Zone.

Be sure only to buy seeds or plants that work well for the area in which you live. 

How to Grow Watermelons from Seeds

watermelon seeds ready for planting

For most watermelon varieties, the best method is directly sowing the seeds. Plant them at least two weeks after your last spring frost date if you directly sow your watermelon seeds.

Unless you live in a dry climate, the best practice for growing watermelons is to on small hills that you mound up.

The mounds provide extra room for the watermelon vines to sprawl out over, and raised mounds also keep water from pooling around the watermelon’s main stem.

Soil needs to be at least 60 degrees Fahrenheit for watermelon seeds to germinate. However, if the soil is between 70-95 degrees Fahrenheit, you will have even more success with germination.

Follow these steps to direct sow watermelon seeds:

  1. Plant the seeds between 3/4 and one inches deep.
  2. Smooth the soil’s surface so that it’s even.
  3. Press three or four seeds flat into the soil’s surface.
  4. Scrape the removed soil to cover the seeds.
  5. Gently pat the surface of the soil so that it has solid contact with the watermelon seeds.
  6. Using a watering can or wand, gently water the watermelon seeds.

Seedlings should germinate within five to ten days, depending on the variety you plant.

Once seedlings have germinated, keep the two most robust seedlings and snip off the weaker seedlings with scissors.

Leave just two plants for every crater or hill.

Transplanting Watermelon Seedlings

If you live in an area with a shorter growing season, you may opt to start your seeds indoors or in a greenhouse. Then, once daytime temperatures reach at least 70 degrees Fahrenheit, you can transplant your watermelon seedlings into your melon patch.

Remember that watermelon plants have a delicate root system, and transplanting them isn’t ideal. For this reason, we recommend planting your seeds in biodegradable peat-free pots so that you don’t have to disturb the root systems of your seedlings.

With biodegradable seed trays, you simply plant your seedlings pot into the soil.

Follow these steps to transplant watermelon seedlings:

  1. Start your seeds indoors in biodegradable pots using a sterile seed starting mix.
  2. Plant three seeds in every pot and cover the seeds with half an inch of potting mix.
  3. Gently water your planted seeds using a spray bottle.
  4. Put your planting trays next to a sunny window, preferably a south-facing one. You can also use a grow light.
  5. Water your seedbeds daily using a spray bottle.
  6. Consider a heat mat to ensure that your seedlings germinate more successfully and quickly.
  7. Once the seedlings are about two inches tall and have some sets of true leaves, it’s time to thin them.
  8. Keep the strongest seedling in each pot. Then, snip off the weaker seedlings with scissors just above the soil’s surface.
  9. About a week following your area’s last frost, begin the process of hardening off your watermelon seedlings. The outside temperature needs to be at least in the 70s. The first couple of days, put your seedlings outside in a location that’s protected for about an hour. Every day, increase the time they spend outdoors and the amount of direct sunlight they receive.
  10. Two weeks after your area’s last frost and when temperatures are in the 70s, your seedlings will be ready to be transplanted outdoors.
  11. Plant two seedlings per crater or hill by trimming the top rims of the biodegradable pots you used so that they are level with the soil.
  12. Dig a hole in the crater or hill that your pot will fit into.
  13. Backfill the hole with soil and water your transplanted seedlings gently.
  14. For the next several days, water the seedlings every day so that they are less likely to experience transplant shock.

How to Grow Watermelon in a Cold Climate

To grow watermelon in colder climates, start your seeds indoors or in a greenhouse. Then, follow the instructions for transplanting watermelon seedlings into your garden.

How to Grow Watermelon in the Desert

If you live in an arid climate, you will need to water your watermelon plants more frequently to supplement rainfall.

Also, when you direct sow your seeds, you need to water your freshly planted seeds every day until the seedlings sprout and grow some true leaves.

Instead of mounds, people growing watermelons in a dry climate benefit from planting their seeds or seedlings in shallow craters. The craters help the plants to conserve moisture.

Craters need to be six inches deep and about two to three feet in diameter.

Spacing Requirements

watermelon plants in garden showing spacing

Craters or mounds should be between three and six feet apart. Rows need to be between six and 18 feet apart. Keep in mind that watermelon vines can become up to 10 feet long.

If you grow smaller watermelon varieties, your seeds or plants can be placed closer together. For best results, follow the instructions on the seed packets.

If you live in a humid climate, your plants may benefit from more generous spacing because this helps with air circulation. With more air circulation, plants are less at risk for disease.

Watermelon Plant Care: How to Grow Healthy Watermelon

Once you have your seeds or seedlings ready to plant, it’s time to get into the details of how to grow watermelon. 

Soil

The soil in your watermelon patch should be moist. However, soggy soil can cause rot. For best results, water your watermelon planting a few hours before you plan to plant your seeds or seedlings. Alternatively, you can plant a few hours after it rains.

For best results in growing watermelon, it’s important to do a soil test to determine your soil’s pH level. The soil test will inform your decisions about the types of fertilizer you need to add to the soil before planting your plants. 

Before you ever plant your watermelon seeds or seedlings, do a soil test so that you will know what types of fertilizer you need to use. The key is to fertilize the soil before planting your seeds or plants. 

The best natural fertilizer option is organic matter, such as well-rotted manure from trusted sources. Ideally, manure should come from livestock that has been fed food that isn’t sprayed with herbicides. 

Another excellent natural fertilizer is compost. Compost and well-rotted manure are perfect for prepping your soil in the spring. 

Sunlight

Watermelon plants thrive in full sunlight. 

Water

Watermelons are made up of about 92% water, so it stands to reason that they need a lot of water to grow. However, it is possible to over-water watermelon plants. 

When seedlings are young or seeds are germinating, they will need to be watered most days so that the soil remains moist. To test your soil’s moisture, use your finger to a depth of one inch. If the soil feels dry, water your plants. 

When plants are well established, they need between one and two inches of water every week. If you get rain, you may not need to supplement with irrigation. If you do water your plants, be sure you water consistently and deeply. 

Once fruits start to ripen, it’s more important to water evenly so that your watermelons don’t crack. When watering becomes erratic, watermelons can crack or split.

To avoid split or cracked melons, go with varieties such as Mini Love, Sugar Baby, or Gold in Gold. 

About a week before your fruit reaches maturity, start withholding water. This will ensure that you have the sweetest possible watermelons as the sugar concentrates in the melons. 

When you water, be sure to water at ground level to avoid getting the foliage wet. Wet foliage is more prone to disease. 

Humidity & Temperature

Once seeds have sprouted, watermelon plants thrive in temperatures between 70 and 90 degrees Fahrenheit during the day. Nighttime temperatures can be between 60 and 70 degrees Fahrenheit. 

Fertilizer

Once your watermelon vines start to grow well, you can begin feeding them with a balanced organic fertilizer.

When the plants begin to fruit, drench the soil with seaweed fertilizer.

Established plants can be fertilized monthly with an all-purpose fertilizer, worm compost, or comfrey tea sprayed on the foliage. 

Mulch

organic watermelon in mulch

Mulching is essential because it helps to maintain moisture around your watermelon plants. However, mulch also serves the purpose of keeping weeds at bay. 

Additionally, mulch such as hay under watermelons helps to keep the fruit off of the soil, where they can be prone to rotting. 

If your area has cooler temperatures, we suggest using darker mulch, such as black plastic mulch. In cooler temperatures, the dark-colored mulch absorbs the daytime heat and releases it back into the plant’s area at night. 

Row Covers

You can protect your watermelon plants from pests by covering them with row covers or garden netting until female and male flowers appear.

Protecting Your Growing Fruit

Once your watermelon plants set fruit, take steps to keep the fruit off the ground. This will help to prevent or control diseases, rot, and pests. One way to do this is to use a melon cradle, sturdy cardboard, or a layer of hay.

If you’re growing vertical watermelon vines, you can use melon hammocks to support the growing fruit.

Pollination

Watermelon plants have separate female and male flowers, and they usually share the same vine. Keep in mind that seedless watermelon varieties also require pollination, or they will fail to set fruit.

One tip is to buy seedless watermelon plants and a few different varieties of watermelon seeds to serve as pollinizers. To get watermelon from the seedless plants, you need to grow both fruit types.

Companion Planting

What is companion planting? Companion planting is planting other plants with your watermelon plants to benefit your melons.

Companion planting can attract valuable pollinators like butterflies and bees to your watermelon patch.

Additionally, companion planting can help deter pests such as vine borers, cucumber beetles, and aphids.

There are three types of companion plants:

  • Banker plants: These plants provide shelter and food for predators that help control pests that prey on your watermelon plants. Also called cover crops, banker plants such as hairy vetch will feed your soil with beneficial organisms, improve nutrient availability for your crop, and build your soil’s organic matter.
  • Repellant plants: The way repellant plants work is by camouflaging the crop’s fragrance, making it more difficult for pests to find the plants.
  • Trap crops: One way to control pests in your garden is to plant something they enjoy more than your watermelon plants. That’s where trap crops come in.

Here are a few excellent watermelon companion plants:

  • Sunflowers
  • Coneflowers
  • Cosmos
  • Herbs such as oregano, mint, rosemary, and thyme
  • Sweet clover
  • Buckwheat
  • Cowpeas
  • Radishes
  • Nasturtium
  • Blue Hubbard squash (to lure cucumber beetles and squash bugs)

Troubleshooting: Common Watermelon Diseases & Pests

No matter how careful the gardener is, every garden experiences pests and/or diseases. Unfortunately, watermelon plants can be susceptible to certain diseases and pests like most plants. 

Watermelon Diseases

Occasionally, watermelon plants can be subject to common diseases.

These include:

  • Blossom-end rot
  • Fusarium wilt
  • Holes and brown lesions (anthracnose)

The best way to prevent disease is to practice good prevention: 

  • Buy seeds and plants from vendors you trust. 
  • Rotate your crops and wait three years before you plant from the same family (cucumbers, other melons, and squash) in the same area. 
  • Use drip irrigation or water at the base of the plants with soaker hoses and watering wands. 
  • Don’t handle plants when they have water on them because this is one-way diseases spread from one plant to another. 
  • Altogether remove infected plants. Don’t till them under or compost them. 

Watermelon Pests

Believe it or not, it’s not just bugs that can wreak havoc on your watermelon patch. Deer love watermelon, so you will need to deer-proof your garden with fencing.

deer in a garden eating plants

Surprisingly, coyotes also enjoy the flavor of watermelon, and fencing will help keep them out. However, coyotes climb fences or dig under the fences instead of jumping them, so you will need to consider different types of fencing if coyotes are a problem in your area. 

Most of a gardener’s woes will come from insects. Here are some more common insect pests that can affect your watermelon plants.

  • Spider mites
  • Melon aphids
  • Cucumber beetle

You can remove aphids and spider mites with a strong water jet from a gardening hose. To control cucumber beetles, use floating row covers until your plants start to flower. 

Harvesting Watermelons

Watermelons don’t continue to ripen off the vine, so it’s essential to know when to harvest them. Alternatively, watermelons can spoil in just a few days if they’re left on the vine for too long. 

How to Tell if Watermelons Are Ripe

Once your watermelons start to become large, it’s time to monitor them daily for progress to see if they’re ripened. There are a few different methods to test for ripened fruit. 

1.) Check the curly tendril.

There is a curly tendril where the fruit is connected to the vine when it’s growing. When watermelon is ripe, these tendrils will become nearly completely dry and start to turn brown. If the curly tendril is green, you know the melon was picked before it was ripe. 

2.) Thump the watermelon’s rind.

When you thump a ripe watermelon, you should hear a deep hollow sound that sounds something like a knock on a door. However, with some varieties, a dull thump can indicate that the watermelon is overripe, so this isn’t the most reliable method. 

3.) Check the field spot, the part of the melon that rests on the ground.

A fully ripened watermelon will have a cream or pale yellow-colored field spot. 

Storing Ripe Watermelons

After harvesting your watermelons, inspect your yield to see if any have cracked. Cracked or split melons should be used immediately. 

Intact melons can be stored at cool temperatures (68-72 degrees Fahrenheit) for seven and ten days. 

Once the watermelon has been cut, it will keep well for up to five days when refrigerated in an airtight container. 

Preserving Watermelon

Watermelon is best eaten fresh and ripe, but there are some things you can do to preserve this sweet fruit. Frozen watermelon is excellent for making fruit smoothies and slushies. 

You can also use frozen watermelon to make watermelon sorbet or ice cream. 

More ideas for preserving watermelon include snacking on the seeds, which is common in other parts of the world. You can also make pickled watermelon rind and watermelon wine. 

Watermelon Nutrition Facts: Is Watermelon Healthy?

Besides being sweet and delicious, watermelon is also remarkably hydrating. This is because watermelons are about 92% water.

In addition to being hydrating, watermelon is also full of vitamins and minerals.

  • Protein
  • Dietary fiber
  • Carbohydrates
  • Vitamin A
  • Vitamin C
  • Potassium

Using Watermelon in Recipes

The best way to eat watermelon is raw and fresh. However, you can try watermelon in countless recipes.

Here are some ideas for using your watermelon harvest:

  • Watermelon cocktails
  • Fruit salad
  • Fruit smoothies
  • Watermelon chunks and other fruit served with sweetened cream cheese fruit dip
  • Watermelon ice cream or sorbet

FAQs

Below, we answer some of the most frequently asked questions about growing watermelon.

How long does it take a watermelon fruit to grow?

It depends on which watermelon cultivar you plant. Some varieties can take up to 100 days or more to produce ripened fruit.

How do I make my watermelon sweeter?

The secret to getting super sweet watermelons is to begin withholding water about a week before the fruit reaches maturity. When the fruit is deprived of water, the sugars will concentrate fully, resulting in a super sweet watermelon. 

To know when your fruit is nearing maturity, count from the time you planted until the variety you planted reaches maturity. 

Should I grow watermelon from plants or seeds?

It depends mainly on your growing season. If you live in a cold climate, consider starting your seeds indoors using biodegradable pots that you can plant along with the seedlings. 

Do watermelon plants return every year?

Unfortunately, watermelon plants are annuals, not perennials. This means that watermelon plants have to be replanted every year.

How many watermelons will I get from one plant?

The number of watermelons you get from each plant will vary depending on which watermelon cultivar you choose to plant. Other considerations are the amount of pollinator activity and the growing conditions in your area.
Generally, you can count on between one and two watermelons per vine.