How to Grow Watermelon

Growing watermelons at home can be a lot of fun if you know the basics of how to grow them. This guide will teach you the basics of how to grow watermelon. Use it and you’ll be growing watermelon in no time!

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Why should you plant Watermelon?

Some scientists think watermelon was first cultivated over 4000 years ago in Northern Africa. This popular red fruit is loaded with nutrients including vitamins A and C, potassium, and Magnesium. It also contains the cancer-fighting compounds cucurbitacin E and lycopene. It’s low in calories, is 92% water so it is very hydrating, and it tastes AMAZING!!

And more importantly, it is fairly easy to learn how to grow watermelon in most backyard gardens. This is especially true if you live in areas with warm summers and more than 120 days of frost-free growing time.

Choosing the right variety of watermelon for your garden

There are a couple of considerations when choosing the varieties of watermelon you will be growing in your backyard garden.

1. First is space. Watermelons grow on large, sprawling, and vining plants. One hill of watermelons can easily take up 20 square feet or more in your garden. So if you don’t have a lot of space you should opt for bush varieties. These specially bred watermelon varieties have a much smaller growing habit, taking up much less space. But with bush varieties, you need to recognize that you will have fewer watermelons per plant and most bush varieties also produce smaller fruit.
2. Second is the length of your growing season. Growing watermelon can be difficult in colder northern climates. Many watermelon varieties require 100+ days to mature and those need to be warm days. So if you live in the north or a cooler climate you should choose smaller “icebox” varieties that have maturity dates closer to 75 days.

Watermelon varieties

There is a huge variety of watermelons out there. Both round and oblong shaped. Melons with red flesh, orange flesh, and pink flesh! Here are a few suggestions:

Bush Varieties (for small spaces)

• Cal Sweet Bush – 90 days – 10 to 12 Pounds – Hybrid Seed
• Bush Jubilee – 90-100 Days – 25 to 35 pounds – Open Pollinated
• Sugar Baby Bush – 75-80 Days – 12 Pounds – Open Pollinated
• Bush Charleston Gray – 90 Days – 10 to 13 Pounds – Open Pollinated

Long Vine Varieties

• Crimson Sweet – 80-97 Days – 30 to 35 pounds – Open Pollinated
• Moon and Stars – 95 Days – Up to 40 Pounds – Open Pollinated
• King of Hearts – 80-85 Days – 14 to 18 Pounds – Hybrid
• Sweet Princess – 85 to 95 Days – 20 to 30 Pounds – Open Pollinated

Short Season Varieties

• Sugar baby – 68 to 86 Days – 8 to 10 pounds – Open Pollinated
• Coles Early – 80 Days – 15 to 20 Pounds – Open Pollinated
• Fordhook Hybrid – 75 Days – 14 Pounds – Hybrid
• Golden Crown – 60 to 70 Days – 5 to 7 Pounds – Hybrid

What are our Favorite Watermelon Varieties?

• Crimson Sweet- This variety bears a nice large fruit in a reasonable 90 days. They are a full-sized melon and the vines sprawl and take up space, but we are rewarded with 3 or more fruits per vine.
• Moon and Stars– This one is beautiful and tasty and takes about 95 days to mature. This variety produces big sweet fruit with more traditional black seeds. Moon and Stars is also a beautiful watermelon variety with yellow spots (the moon and stars) on a dark green background!
• Sugar Baby – This one is always a producer in our garden. Even in cooler years when the longer maturing varieties don’t produce well, Sugar Baby is a star. Its smaller fruits are ready in as little as 68 days and each vine produces 2 or 3 tasty fruits!

Planting Watermelon – Seeds vs Transplants

Like all other members of the Cucurbit family, Watermelon does best when seeds are directly sown in the garden. Watermelon is very frost sensitive so planting should be done 7 to 14 days after your average last frost date. It is best to wait until the soil temperatures reach at least 65 degrees Fahrenheit (18 celsius).

Watermelon seeds are normally planted in “hills”. “Hills” are simply small mounds of soil. Create a small “hill” that is about 12-18 inches round (30-45 cm). Enrich the soil with a generous helping of compost if compost wasn’t added earlier in the year. Also now would be the time to add a balanced fertilizer to the soil if you feel like your garden soil is lacking.

In each “hill” plant 6 seeds, you should sow seeds spaced about 3 inches (7.5 cm) apart around the hill. Seeds should be planted an inch deep (2.5 cm).

Many experts recommend that if you live in a very arid climate it may be beneficial to plant your watermelon seeds in a small crater instead of a hill. This will help with water retention.

Once the seeds have germinated and the first set of true leaves have appeared you should select the 3 strongest seedlings in each hill and thin the weaker seedlings.

Planting Watermelon by Transplants

Members of the cucurbit family, including watermelon, do not like having their roots disturbed after the seeds have germinated. This is the main reason why we recommend direct seeding whenever possible.

However, if you live in a very cold climate with short growing seasons, it may be necessary to start your watermelons using transplants that you have either grown yourself or bought at a nursery.

To minimize root disturbance you should grow your watermelon seedlings using either pots made from newspaper, using peat pots, or using soil blocks. These types of pots can be directly planted in the ground without removing the plant from the container reducing how much we disturb the roots.

Smaller watermelon plants will have less transplant shock than larger plants that have started vining. So when growing your seedlings you should only start them 3-4 weeks before you intend to set them out in the garden. We want transplants with only 1 or 2 sets of true leaves.

Watermelon transplants should be started in a warm area, using a heat mat to help warm the seedling mix. Shop lights or grow lights should be used to ensure the plants have the appropriate amount of light. Keep the lights close to your seedlings to help prevent legginess. You can learn more about growing seedlings by downloading our Free Seed Starting eBook here.

Buying Watermelon Transplants

When buying watermelon transplants look for small compact plants with only 1 or 2 sets of true leaves. Plants should be small and healthy-looking, be sure to check for pests and diseases.

Hardening Off Watermelon Transplants

Whether you grow your own seedlings or buy them from a local nursery you should harden your transplants before setting them out. Hardening Transplants is the process of slowly introducing the seedlings to the conditions in the garden over the course of 7 to 10 days.

This will help strengthen the transplants and reduce transplant shock. Be sure to include hardening time in your planting date calculations. If you would like to learn more about hardening off check out this article on our website.

How to care for Watermelon Plants

Sunlight requirements for Watermelon

As fruiting plants, watermelons will need as much sun as possible. Watermelon should be planted in areas that receive full sun (defined as at least 6 hours per day). Watermelon plants love lots of hot sunshine, so you should try to plant them in areas that get 8 or even more hours of sunlight each day during the summer months.

Soil Requirements

Growing watermelon is best done in rich, well-drained, slightly sandy soils. But watermelons will do well in almost any type of soil as long as it is well drained.

Amend your soil with around an inch of compost or well-aged manure mixed into the top few inches of soil before planting. If your soil needs it you can also add a balanced fertilizer to the soil before planting (mix well into the top 6 inches of the soil)

How much Water does a Watermelon plant need?

Growing watermelons require between 1-2 inches of water a week depending on weather conditions, so you should plan on irrigating at least twice a week.

Drip irrigation systems are the best option for watermelon plants. The slow even watering of a drip system will help build deep roots for your plants. Overhead watering should be avoided if possible as it tends to promote diseases and fungal infections in your watermelons.

Be sure to be consistent with your watermelons. Keeping the soil consistently moist will help prevent cracking as your fruit is developing. Constant cycles of drying out and then lots of water can cause developing fruit to crack as it grows.

Consistent water levels are also very important for good flavor in your watermelons.

Mulch can help to keep your soil moisture even. Mulches like shredded leaves, grass clippings, or even compost will help protect your plants.

Weeding

Like most garden crops, watermelon doesn’t like competition. Keep the weeds down to improve your crop. Mulches can help with this!

Add Mulch under the Fruit

The simple habit of adding a little mulch underneath your growing watermelons can help keep the fruits in good shape. Gently lift the developing fruits and cover the bare ground with mulch, straw, or even some cardboard. This will help prevent the fruits from rotting and will also limit soil-borne pests from snacking on the fruit.

Common Pests and Diseases

Healthy watermelon plants are usually fairly resistant to most pests, but can be susceptible to any of the following pests:

• Aphids
• Squash Bugs
• Squash vine borers
• Cucumber Beetles
• Grasshoppers
• Whiteflies
• Cabbage Loopers
• Flea Beetles
• Click Beetles
• Thrips
• White Grubs

I have found that watermelons grown in a backyard garden end up being fairly pest-free, that is mainly because if you have a garden with a variety of plants, most of the pests will prefer something else in the garden and leave the melons alone.

Growing watermelon with plants like marigolds, nasturtium, and dill will also help as those plants tend to repel most pests.

Watermelons are also susceptible to diseases like powdery mildew, downy mildew, bacterial wilt, and viruses. Good Crop rotation practices and planting resistant varieties can help with these issues.

How to tell when a watermelon is ripe and ready to pick?

Individual watermelon fruits usually take between 35 to 45 days from flowering to reach full maturity depending on weather conditions and variety. Getting the timing right on picking a watermelon is important because a watermelon will NOT continue to ripen once it has been harvested.

In colder northern areas you should start removing all flowers from your vines about 50 days before your average first frost. This allows the plant to focus its energy on ripening the existing fruit without having to worry about growing any additional fruit that will not ripen in time.

If you want to learn more about when to pick melons in general read this article.

5 Signs your watermelon is ready to pick

1. Days since flowering

You can start tracking time to maturity once you notice a fruit has “set”. They will usually mature in about 35 to 45 days after the fruit has set.

2. Thump your Melons

Make a fist with your hand and thump it on your chest. Do you hear the sound that thumping makes? Now thump your watermelon. The sounds should be similar. If they are, this is the first sign your melon is getting ripe, but don’t just use this as your determining factor.

3. Skin Color

As a melon approaches maturity its skin color will change from a shiny color to a dull one. This is another indication the melon is ready.

4. Ground Spot Color Change

As final maturity is getting close the “ground spot” (the spot where the melon is touching the ground) will change color from white to yellow. This is also another good indication that the melon is about ready to pick.

5. Vine Tendril Dries Up

The best way to tell if your watermelon is ready to pick is to watch the curly tendrils closest to the melon. If you look closely you will see these little tendrils growing on the watermelon vines. There will be a tendril fairly close to the watermelon you think is ready.

Initially, this tendril will be green, and “pigtail” curly. As your watermelon reaches ripeness the tendril closest to the melon will dry out and become brown and hard. Once that tendril has completely dried out (see the photo below) then it is time to pick your watermelon. Do not wait for too long after this tendril dries as the melon will overripen.

Harvest and Storage of Watermelons

You should use a nice sharp pair of pruning shears or a sharp knife to harvest your watermelon. Trying to pull or twist the vine to remove the fruit risks damage to the plant and can then affect the other melons that are still ripening.

Watermelon can be stored for 1 to 2 weeks if held in a fridge at between 45-50 F (7-10 C). They won’t last long so eat them up quickly.

Watermelon can be frozen and used later as an ingredient for smoothies and it can also be made into fruit leather. But other than that there aren’t any viable methods for preserving watermelon long-term.

Short on space? Grow vertically!

If you have a small garden with little ground space then you could consider growing watermelons vertically! Watermelon vines will climb trellises very well and the added air circulation can help reduce both pest problems and powdery mildew issues. A cattle panel trellis can be ideal for growing watermelons.

Many watermelon varieties grow very large and heavy fruits which would need excessive support when growing vertically. So when you are choosing a variety to grow on a trellis you want to select smaller fruit varieties. Most “Icebox varieties” will do well on a trellis. These Varieties include Blacktail Mountain, Sugar Baby, and Sweet Beauty.

Also, keep in mind that you will need to support the fruit on watermelon grown vertically. You can do this with old nylon stockings or there are commercially available melon hammocks that you can buy to give them the support they need.

Watermelon Questions and Answers

No fruit is developing on my Watermelon Plant?

The first thing to check is for pollination. Do you have bees and other pollinators visiting your watermelon plants? If not you may have to hand-pollinate your watermelon flowers using the technique described above.

Next, check your watering, is the plant stressed from not having enough water? It should be getting around 1-2 inches per week depending on the time of year.

Also, remember to be patient. Early in the season most cucurbit family plants only produce male flowers. This is a natural process that starts attracting bees and other pollinators. A few weeks into the process you should start to see more female flowers.

Should I prune my overgrown watermelon plants?

No! Studies have shown that the sugars that sweeten your watermelon come from the leaves on the vines. Fewer leaves mean less sweetness in the fruit. So don’t worry about pruning your plants.

Can I grow Seedless Watermelons at home?

Yes, but it is tricky! Seedless watermelons are hybrids and they don’t produce enough pollen in their male flowers to pollinate the female flowers. So you have to grow a second variety of watermelon to act as a “pollinator cultivar” to provide enough pollen for the fruit.

Seedless watermelon seeds are also fairly expensive and should be started indoors to be transplanted out in the garden later.

Growing seedless varieties at home is possible, it just takes more space and work than regular melons. Would you like to get more details on growing seedless watermelons? I found a great article that goes into more detail here.

Should I put black plastic down when planting watermelons?

Using black plastic or black landscape fabric as mulch can be helpful with watermelons. The black plastic acts as a mulch, keeping weeds down, keeping water in, and raising the soil temperature around your watermelon plants. All of this combines to produce stronger, faster-growing watermelon plants.

This is particularly helpful in cooler northern climates. Using black plastic mulch isn’t really necessary in warmer southern climates with long growing seasons.