How to Grow Watermelons – 7 Essential Tips

A sweet, juicy slice of watermelon fresh from your garden is a real treat on those sunny summer afternoons. Despite their long growing season, growing watermelons isn’t as tricky as you might think. This post covers all the essentials about how to grow watermelons at home.

Watermelons are large vining plants that have a sprawling growth habit. They originated in Africa’s Kalahari Desert and are part of the Cucurbitaceae plant family, along with cantaloupe, gourds, pumpkins, cucumbers, and squash.

Watermelons are as nutritious as they are delicious. They’re an excellent source of plant-based fiber and are rich in vitamins A, C, and B1, B5, and B6. Watermelon also contains antioxidants like carotenoids, lycopene, and cucurbitacin E. These nutrients help reduce inflammation, improve digestion, support eye and heart health, and promote healthy skin and hair. Additionally, eating water-rich foods like watermelon keeps you hydrated and helps you to feel fuller, both of which aid weight loss.

Watermelons are straightforward to grow in most climates as long as you can provide rich, well-draining soil and plenty of sunshine. Keep reading to discover the best tips and tricks for enjoying a bountiful harvest of delectable melons.

Best Tips on How to Grow Watermelons

Watermelon plants need at least 70 days of warm weather above 65℉ to ripen. Gardeners in cooler climates can get a head start on the growing season by starting seeds indoors in early spring or transplanting nursery-grown seedlings after the last danger of frost passes.

The optimal temperature range for growing watermelons is between 65-90℉. They require full sun, with six or more hours of direct sunlight throughout the day.

Consistently moist soil is critical for growing watermelons. On average, give your watermelon plants one to two inches of water per week. It’s beneficial to use drip irrigation or a soaker hose rather than overhead watering to avoid getting the leaves wet, which increases the risk for fungal diseases.

Pollination is vital for getting a satisfactory watermelon crop. The plants grow separate male and female flowers and need help from pollinators like bees and butterflies. Male flowers feature a stamen that produces pollen, and female flowers contain a pistil for receiving pollen. Female flowers also have a small, swollen node at their base (their “lovely lady lumps”) where the fruit will eventually develop. Plant aromatic herbs and flowers close by to attract pollinating insects to your garden.

One of the greatest parts of growing your own groceries is trying unusual varieties of fruits and veggies that aren’t available at grocery stores or farmer’s markets. Here are some of the best watermelon cultivars for home gardens.

Top Watermelon Varieties

• Allsweet (heirloom, 25-30 pound fruits, green striped rind, bright red flesh, disease-resistant, 90-105 days to harvest)
• Golden Midget (heirloom, 3-4 pound fruits, gold rind when ripe, salmon pink flesh, fast-growing, 60-90 days to harvest)
• Lemon Drop (heirloom, 1-2 pound fruits, yellow rind, golden flesh, early producer, 65-70 days to harvest)
• Lil Red Rock (hybrid, 5-7 pound fruits, green striped rind, bright red flesh, seedless, high-yielding, disease-resistant, 75-80 days to harvest)
• Mini Love (hybrid, 3-6 pound fruits, green striped rind, dark red flesh, high-yielding, disease-resistant, resists cracking/splitting, 70 days to harvest)
• Moon and Stars (heirloom, 10-20 pound fruits, green rind with yellow markings, pink flesh, disease-resistant, drought/heat-tolerant, 95-100 days to harvest)
• Orange Krush (hybrid, 15-20 pound fruits, green rind, orange flesh, disease-resistant, 75-80 days to harvest)
• Sugar Baby (heirloom, 8-10 pound fruits, green rind, bright red flesh, drought-tolerant, disease-resistant, 75-80 days to harvest)

How to Grow Watermelons from Seeds

Since they have a long growing season, most gardeners plant watermelon seeds indoors two or three weeks before the expected last frost date. In warm climates, sow seeds directly in the garden two weeks after the last spring frost or whenever the soil temperature is consistently above 70℉. The ideal temperature for germination is 80-85℉.

You’ll require a few supplies for starting watermelon seeds indoors. Find these items at your local garden center if you don’t already have them at home.

Seed Starting Supplies

• Organic watermelon seeds
• Seedling tray with two-inch cells
• Seed starting potting mix
• Heat mat
• Grow light
• Humidity dome
• Clean spray bottle

Fill your seedling tray, peat pots, or a repurposed cardboard egg carton with well-draining, nutrient-rich potting soil. It’s beneficial to pre-moisten the soil before planting your watermelon seeds.

Sow the seeds a half-inch deep and lightly cover them with soil. Top your tray with a humidity dome or sheet of plastic wrap to maintain soil moisture during germination, which typically takes four to ten days.

Keep the soil consistently warm. Watermelon seeds won’t germinate if the soil temperature is below 70℉ or above 95℉.

When the seedlings emerge, move the seedling tray to a sunny windowsill that gets a minimum of six hours of bright light each day. Alternatively, use grow lights to avoid letting your seedlings become elongated or “leggy” from not receiving enough sunlight. Rotate the tray every few days to encourage strong stem growth, and keep the seedlings well-watered.

Watermelon seedlings are very cold-sensitive and die if exposed to temperatures below freezing. Wait two weeks after your typical last frost date to transplant them outdoors.

Prime Growing Conditions for Watermelons

Watermelon plants flourish in garden soil that’s well-draining and rich in organic matter. Cover the planting area with a generous layer of organic compost, dark-colored mulch, or a sheet of black plastic for seven to ten days before transplanting to raise the soil temperature.

Like most other fruits and veggies, watermelons prefer neutral to slightly acidic soil with a pH level between 6.0 and 7.0. Contact your district extension service for a soil test if you’re unsure of your soil pH level.

Helpful soil amendments include organic compost, well-aged manure, kelp meal, and bone meal. Mulching with organic materials like bark chips, grass clippings, leaves, pine needles, or straw helps to retain moisture, insulate and protect the soil, and minimize weed growth. Planting watermelons on small mounds or hills keeps the soil warmer and facilitates water drainage away from the plant’s main stem.

Some gardeners opt to grow watermelons on a trellis to save ground space and provide better air circulation. Smaller cultivars are easy to trellis. However, with the proper support, it’s also possible to train larger varieties to climb a trellis.

Watermelons aren’t natural climbers. Loosely tie the vines to your trellis structure. Soon, the curly tendrils will begin wrapping themselves around the lattice. Support heavy fruits with flexible fabric tied to the framework like small hammocks. Pieces of old T-shirts or pantyhose work well.

Choosing the Right Watermelon Fertilizer

Watermelon plants are heavy feeders. They benefit from regular fertilizing throughout the growing season. Plant fertilizer contains three primary macronutrients: nitrogen (N), phosphorus (P), and potassium (K). Nitrogen encourages leafy growth, phosphorus supports robust root systems, and potassium boosts the fruiting and flowering processes.

For the best possible results, add one tablespoon of all-purpose, organic fertilizer to the bottom of each hole when transplanting your watermelon seedlings. Add another dose of slow-release fertilizer to the soil around the plant’s base after four to six weeks. Once your watermelons start flowering, switch to a fertilizer with higher levels of phosphorus and potassium to enhance fruit production.

Keep in mind that overfertilizing damages the microbiome in your garden soil and can inhibit plants from absorbing nutrients from the earth. Always follow the listed instructions, and test your soil to find out which nutrients you need to add.

How Long Do Watermelons Take to Grow?

Are you wondering, “Just how long do watermelons take to grow?” The answer is that it depends on the cultivar. Certain varieties, especially those that bear miniature watermelons, mature faster than the larger types. Watermelons take an average of 70-110 days from planting seeds to harvest time.

After the plant begins flowering, it usually takes around 45 days for the melons to ripen. Watermelons won’t continue ripening off the vine, so it’s crucial not to pick them too soon.

There are several noticeable indicators of a watermelon’s ripeness. Depending on the variety, the rind will usually change color when it’s ready to get picked, or the markings (stripes or spots) will disappear.

Another reliable method for checking ripeness is to press on the melon gently. If it still feels firm, wait a little longer. If the rind gives a bit, it’s ready.

In addition, you can observe the curly tendril growing from the melon’s nearest leaf node. The watermelon isn’t mature yet if that tendril is still bright green. When the tendril dries out and turns brown, the melon is ripe. For more tips on how to tell if a watermelon is ripe, check out this post from Iowa State University.

Harvesting and Storing Your Homegrown Watermelons

Harvest watermelons with a clean, sharp knife or pair of pruners to prevent accidental damage to the main stem or vines when harvesting watermelons. Always sterilize your garden tools between uses to avoid spreading diseases between plants. Watermelons will stay fresh longer if you leave two inches of the stem intact.

Store an uncut watermelon in the fridge for up to 10 days. Watermelons usually keep for around four days after slicing into them. Wrap any leftovers tightly in beeswax food wrap or plastic film. Or, store them in a lidded container in your refrigerator’s crisper drawer.

Solutions for Common Pest and Disease Issues

It’s vital to monitor your watermelon plants for symptoms of pest and disease problems. Healthy plants are considerably less vulnerable to attacks from insects and pathogens. Their best defense is getting appropriate amounts of light, nutrients, and water.

Some of the most commonplace insect pests for watermelons include aphids, spider mites, cucumber beetles, and vine borers. After transplanting, cover the seedlings with floating row covers to prevent insects from laying eggs in the nearby soil or on the leaves. If you have a severe insect infestation, spray all parts of the plant (especially the undersides of the leaves) with an organic insecticide like horticultural oil, neem oil, or insecticidal soap.

Prevalent plant diseases that affect watermelon plants are powdery mildew, anthracnose, fusarium wilt, and stem blight. These fungal diseases spread quickly in warm, humid conditions and frequently get transported via splashing water droplets. Provide appropriate spacing and sufficient airflow and water with a soaker hose or drip irrigation to keep the leaves dry. Remove any affected leaves and treat the plants with an organic copper or sulfur fungicide. If you’ve had issues with these diseases in the past, be sure to plant disease-resistant cultivars.

Companion Plants for Watermelons

Companion planting is a time-honored garden design strategy that takes advantage of favorable interactions between compatible plants. Many plants attract beneficial insects like pollinators and predators, repel common garden pests, and enhance their neighbors’ flavor and overall vitality. However, some plants are known to hinder one another’s growth and must grow separately.

Marigolds, nasturtiums, and radishes are outstanding companion plants for watermelons. They ward off insect pests like cucumber beetles, aphids, and whiteflies. Alliums like chives, onions, and garlic repel aphids, whiteflies, spider mites, rodents, and deer.

Dill is immensely helpful around the garden, thanks to its ability to repel numerous insect pests like aphids, spider mites, and cucumber beetles. This aromatic herb also attracts beneficial predatory insects that help control pest populations, including hoverflies, lacewings, ladybugs, and parasitic wasps (which don’t sting humans.) Oregano also fends off cucumber beetles, and it attracts predators and pollinators, too.

Flowering plants like borage, chamomile, cosmos, calendula, and lavender help to bring pollinators to your garden. Planting a border of wildflowers around your garden helps to attract native bees.

Plant potatoes and sage away from watermelons, as these plants reportedly stunt one other’s growth. Additionally, it’s best not to plant crops vulnerable to the same kinds of pest and disease problems close together. Therefore, avoid growing watermelons near other cucurbits like cantaloupe, cucumbers, pumpkins, or squash.

Watermelons are a delightful addition to any food garden. Since they require a relatively long, warm growing season, planting watermelon seeds indoors in early spring is advantageous. There are numerous unique varieties to choose from – grow small or large fruits, seedless melons, or even orange and yellow watermelons. The possibilities are infinite, and the final results are heavenly.

Do you have any recommendations or questions about how to grow watermelons? Please share them in the comments! If you enjoyed learning more about growing watermelons, please share these gardening tips with your fellow green thumbs.