Watermelons, with their juicy sweetness and refreshing appeal, are fun to grow in the garden.
Just like their pumpkin cousins, watermelons demand ample space and sunlight to thrive, making them ideal candidates for larger garden plots. In this guide for how to grow watermelon, we’ll explore the essentials of growing watermelons, from selecting the right varieties to nurturing them to harvest.
We’ve grown many watermelon over the years in our zone 5b (now 6a) garden zone and will share everthing we’ve learned.
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Growing Watermelons: Quick Facts
Best Time to Plant: After the last frost date in your area, when soil temperatures reach at least 70°F (21°C)
Soil pH: 6.0-6.8, slightly acidic to neutral
Soil Type: Well-draining loamy soil with good fertility
Sunlight: Full sun, at least 6-8 hours per day
Watering: Consistent watering, aiming for 1-2 inches per week, increasing during hot, dry periods
Fertilizing: Use a balanced fertilizer or compost before planting, and side-dress with nitrogen-rich fertilizer during the growing season. We do not fertilize our watermelon but plant into compost rich soil.
Plant Spacing: Plant seeds or seedlings 2-3 feet apart in rows spaced 6-8 feet apart, allowing ample room for vines to spread
Common Pests: Aphids, cucumber beetles, squash bugs, and powdery mildew
Companion Planting: marigolds, nasturtiums, or radishes can help repel pests; consider planting corn or beans as companions for mutually beneficial growth. See more about Companion Planting Watermelon.
Harvest Time: Generally 80-90 days after planting, when the tendril nearest the fruit turns brown and the underside of the watermelon changes color from white to yellowish. You will want to check the specific varieties and make sure your growing season in long enough to grow that variety.
Selecting the Best Watermelon Variety
There are many varieties of watermelon that come in lots of sizes, shapes and even colors. Pay attention to the days to harvest to make sure you can grow the variety in your zone. We’ve typically found the smaller varieties a bit easier to grow. Below are some of the most popular varieties.
Sugar Baby Watermelon: This variety is a favorite among home gardeners for its compact size and sweet, crisp flesh. Sugar Baby watermelons typically weigh between 8-10 pounds, making them perfect for smaller gardens or containers. With a dark green rind and bright red flesh, they’re a classic choice for summertime snacking.
Crimson Sweet Watermelon: Known for its excellent flavor and high sugar content, the Crimson Sweet watermelon is a popular choice for home growers and market gardeners alike. These melons can reach up to 25 pounds and have a striking green-striped rind with sweet, juicy red flesh. They thrive in warm climates and are resistant to many common diseases.
Charleston Gray Watermelon: Dating back to the 1950s, the Charleston Gray watermelon remains a beloved heirloom variety cherished for its sweet, firm flesh and thin rind. These oblong-shaped melons can weigh up to 30 pounds and have a light green rind with distinct darker green stripes. They’re well-suited for hot, humid climates and have good resistance to pests and diseases.
Black Diamond Watermelon: With its large size and rich, sweet flavor, the Black Diamond watermelon is a standout choice for those looking for a show-stopping fruit. These melons can weigh up to 50 pounds or more, featuring a dark green rind and deep red, juicy flesh. While they require a longer growing season, the reward is worth the wait, as they’re a favorite at picnics and gatherings.
How to Grow Watermelons
When to Plant Watermelon
Watermelons are warm-season crops that thrive in temperatures above 70°F (21°C), so it’s important to wait until after the last frost date in your area before planting them. Typically, this means planting watermelon seeds or seedlings outdoors when soil temperatures have warmed to at least 70°F (21°C) and all danger of frost has passed. Depending on your location, this could range from late spring to early summer. Aim for a time when the soil is warm and the weather is consistently mild, as watermelons require warm conditions to germinate and grow successfully.
It’s possible to start seeds indoors and transplant outside after frost although this is mostly recommended when you have a short growing season, otherwise I prefer to plant watermelon directly outside.
How to Plant Watermelons
Planting watermelons is relatively straightforward.
Start by choosing a sunny location with well-draining soil, as watermelons thrive in full sun and dislike soggy conditions. Prepare the soil by loosening it to a depth of at least 12 inches and incorporating organic matter like compost or aged manure to improve fertility and drainage. Like pumpkkins, watermelon are fairly heavy feeders.
When planting seeds directly in the ground, sow them about 1 inch deep and space them 2-3 feet apart in rows spaced 6-8 feet apart to allow ample room for vine growth. this spacing depends on the variety and smaller varieties can often be grown closer together. Check your seed packet for more specific information.
If starting with seedlings, transplant them into the garden at the same spacing once they have developed a few true leaves. Keep the soil consistently moist but not waterlogged, especially during the germination and early growth stages.
Watermelon Care and Maintenance
Once your watermelon vines begin to grow, it’s important to provide consistent watering, aiming for about 1-2 inches of water per week, especially during dry periods or when fruits are developing. Watermelon require more water than most other crops.
Mulching around the plants can help retain soil moisture, suppress weeds, and maintain even soil temperatures. Additionally, regular fertilization is key to supporting vigorous growth and fruit production. Monitor the plants for any signs of pests or diseases, such as aphids, cucumber beetles, or powdery mildew, and take prompt action to address any issues. As the watermelons mature, provide support for larger fruits by placing them on straw or boards to prevent rotting and ensure even ripening.
Harvesting and Storing Watermelon
Harvesting watermelon at the peak of ripeness is key to enjoying their sweet, juicy flavor.
Typically, watermelons are ready for harvest around 80-90 days after planting, depending on the variety and growing conditions. One indicator of ripeness is the tendril closest to the fruit, which will dry up and turn brown when the watermelon is ready to be picked. Additionally, the underside of the watermelon will change color from white to yellowish.
When harvesting, use a sharp knife or shears to cut the stem about 1-2 inches above the fruit. Be careful not to damage the vine or the fruit itself. After harvesting, watermelons can be stored in a cool, dry place for up to two weeks. Alternatively, they can be refrigerated for longer shelf life, but keep in mind that cold temperatures can affect the flavor and texture.
Enjoy your freshly harvested watermelons in salads, desserts, or simply sliced and enjoyed on a hot summer day.
Best Tips for Growing Watermelon
- Choose a sunny location: Watermelons thrive in full sun, so select a spot in your garden that receives at least 6-8 hours of sunlight per day.
- Prepare the soil: Ensure the soil is well-draining and rich in organic matter by incorporating compost or aged manure before planting.
- Plant at the right time: Wait until after the last frost date in your area and soil temperatures have warmed to at least 70°F (21°C) before planting watermelon seeds or seedlings.
- Provide consistent watering: Aim for about 1-2 inches of water per week, especially during dry periods or when fruits are developing, and mulch around the plants to retain moisture.
- Support vine growth: Space watermelon plants 2-3 feet apart in rows spaced 6-8 feet apart to allow ample room for vine growth, and provide support for larger fruits as they develop.
- Monitor for pests and diseases: Keep an eye out for common pests like aphids, cucumber beetles, and squash bugs, as well as diseases like powdery mildew, and take prompt action to address any issues.
- Harvest at the right time: Look for signs of ripeness such as the tendril closest to the fruit drying up and turning brown, and the underside of the watermelon changing color from white to yellowish before harvesting with a sharp knife or shears.
Common Watermelons Problems and Solutions
Powdery Mildew: Powdery mildew is a fungal disease that appears as a white powdery substance on the leaves, eventually causing them to yellow and die. To combat powdery mildew, ensure proper air circulation by spacing plants adequately, avoid overhead watering, and apply fungicides early in the season as a preventive measure. Additionally, removing and destroying infected plant material can help prevent the spread of the disease.
Blossom End Rot: Blossom end rot is a physiological disorder characterized by water-soaked lesions at the blossom end of the fruit, leading to rotting. This condition is often caused by calcium deficiency or fluctuations in soil moisture levels. To prevent blossom end rot, maintain consistent soil moisture by watering evenly and avoiding periods of drought or waterlogging. Incorporating calcium-rich amendments into the soil, such as gypsum or lime, can also help prevent this issue.
Pests (Aphids, Cucumber Beetles, Squash Bugs): Various pests can infest watermelon plants, feeding on foliage, stems, and fruits, ultimately affecting plant health and reducing yields. To control aphids, cucumber beetles, and squash bugs, employ natural predators like ladybugs and lacewings, manually remove pests from plants, and use insecticidal soaps or neem oil as organic control methods. Implementing crop rotation and practicing good garden hygiene can also help reduce pest populations over time.
Fusarium Wilt: Fusarium wilt is a soil-borne fungal disease that causes wilting, yellowing, and eventual death of watermelon plants. To manage Fusarium wilt, plant resistant varieties whenever possible and avoid planting watermelons in areas where susceptible crops have been grown in previous seasons. Additionally, ensure proper soil drainage and avoid overwatering, as wet conditions can exacerbate fungal growth. If Fusarium wilt is detected, remove and destroy infected plants promptly to prevent the spread of the disease.