How to Grow Watermelons in North Dakota

How to Grow Watermelons in North Dakota

Growing watermelons in North Dakota can be a rewarding challenge due to the state’s short growing season and cooler climate. However, by selecting the right variety, using proper techniques, and carefully timing your planting, it’s possible to produce sweet, juicy watermelons even in this northern state.

1. Understanding North Dakota’s Climate for Watermelons

Watermelons need warm temperatures, typically between 70-85°F, to grow and develop properly. North Dakota’s growing season is relatively short, often lasting from May through September, so it’s important to take advantage of every warm day available.

• Frost Dates: The last frost in North Dakota usually occurs in mid- to late May, while the first frost often hits by mid-September. This gives growers roughly 100-120 frost-free days, which is tight but manageable with the right planning.
• Heat Requirements: Watermelons thrive in heat, so maximizing sunlight exposure and using techniques to extend warmth, like black plastic mulch, is essential.

2. Choosing the Right Watermelon Varieties

Selecting watermelon varieties that mature quickly is crucial for success in North Dakota. Look for varieties with shorter growing periods and good cold tolerance.

• Sugar Baby: A popular choice for northern climates, this small, round watermelon matures in about 75 days and weighs around 8-10 pounds.
• Blacktail Mountain: Developed in northern Idaho, this variety matures in 70-75 days and is known for its cold tolerance, making it ideal for North Dakota.
• Crimson Sweet: A larger variety that can mature in about 80 days, producing watermelons up to 25 pounds.

3. Starting Watermelons from Seeds

Watermelons can be direct-seeded into the garden, but starting seeds indoors can help get a head start on the season.

• Indoor Planting: Start seeds indoors 2-3 weeks before the last frost date (late April to early May). Use peat pots or biodegradable containers, as watermelons don’t like having their roots disturbed when transplanted.
• Sowing Depth: Plant the seeds about ½ inch deep in a warm, sunny spot. Water the seedlings regularly and keep the temperature between 70-80°F for optimal germination.

4. Transplanting Watermelons Outdoors

Once the soil has warmed to at least 65°F (usually by late May or early June), transplant your watermelon seedlings into the garden.

• Site Selection: Choose a sunny spot with well-drained soil. Watermelons need 6-8 hours of direct sunlight each day.
• Soil Preparation: Watermelons prefer loose, sandy soil with a pH of 6.0-6.8. Before planting, work compost or aged manure into the soil to improve fertility and moisture retention.
• Spacing: Space plants about 3-4 feet apart in rows that are 6-8 feet apart. Watermelons are sprawling vines and need plenty of space to grow.

5. Using Black Plastic Mulch

Black plastic mulch is a useful tool in North Dakota’s cooler climate. It helps to warm the soil, retain moisture, and suppress weeds.

• Lay Mulch Early: A few weeks before transplanting, spread black plastic mulch over the planting area. The mulch will absorb sunlight, keeping the soil warm even during cooler nights.
• Cutting Holes for Plants: When transplanting, cut small holes in the mulch to plant the watermelon seedlings.

6. Watering and Fertilizing

Consistent watering is essential for growing watermelons, particularly during the fruiting stage.

• Watering: Water deeply once or twice a week, aiming to provide about 1-2 inches of water. Be careful not to overwater, as watermelons prefer slightly dry conditions once the fruit has set.
• Fertilizing: Side-dress the plants with a balanced fertilizer (such as 10-10-10) when they start to vine. Once the fruit begins to grow, switch to a fertilizer high in phosphorus and potassium to encourage fruit development.

7. Pollination

Watermelons rely on bees and other pollinators for successful fruit set. Make sure your garden is pollinator-friendly by avoiding insecticides that harm bees and planting flowers nearby to attract them.

• Hand Pollination: If pollinators are scarce, you can hand-pollinate by transferring pollen from male flowers to female flowers with a small paintbrush or cotton swab.

8. Pest and Disease Management

Although North Dakota’s cooler climate reduces the risk of some pests, watermelons can still face challenges.

• Cucumber Beetles: These pests can damage watermelon vines. Use row covers early in the season to protect young plants and remove covers once flowering begins.
• Fusarium Wilt: This soil-borne disease can cause wilting and yellowing of leaves. Rotate crops and avoid planting watermelons in the same spot year after year.

9. Harvesting Watermelons

Knowing when to harvest your watermelons is crucial, as they don’t ripen off the vine.

• Check for Ripeness: Watermelons are ripe when the tendril closest to the fruit turns brown, the underside of the melon turns yellow, and the skin loses its shine.
• Harvest Time: Most varieties will be ready to harvest 75-85 days after transplanting, depending on the weather and variety.

10. Storing Watermelons

After harvesting, watermelons can be stored for up to two weeks at room temperature or longer in a cool, dry place.

Conclusion

Growing watermelons in North Dakota may seem challenging, but with the right timing, variety selection, and techniques like using black plastic mulch, you can enjoy a successful harvest. By starting seeds indoors, giving them plenty of warmth, and providing consistent care, you can produce sweet, juicy watermelons even in the northern climate.