How to Grow Watermelon in New Hampshire

How to Grow Seedless Watermelon

Growing watermelons in New Hampshire requires careful planning and attention to detail, but the sweet reward of harvesting these juicy fruits makes it well worth the effort. With the right variety, site selection, and cultural practices, you can successfully grow watermelons in the Granite State's cooler climate.

Choose the Right Watermelon Variety

Selecting a watermelon variety well-suited to your specific growing conditions is crucial for a bountiful harvest. When growing watermelons in New Hampshire, prioritize varieties with a shorter growing season, disease resistance, and appropriate fruit size.

Watermelons require a long, warm growing season, typically 80 to 100 days from planting to harvest. However, varieties with a shorter maturity period, around 70 to 80 days, are better suited for New Hampshire's cooler climate. Some excellent early-maturing options include 'Sugar Baby,' 'Blacktail Mountain,' and 'Crimson Sweet.'

Days to Maturity

Look for watermelon varieties labeled as "early" or "extra-early" to ensure they can reach full maturity before the first fall frosts. These varieties have been bred to produce ripe fruit in a shorter timeframe, increasing your chances of success in New Hampshire's shorter growing season.

Disease Resistance

New Hampshire's humid summers create an ideal environment for various fungal diseases, such as anthracnose, fusarium wilt, and gummy stem blight. Choosing disease-resistant varieties can help mitigate these risks. 'Crimson Sweet,' 'Sangria,' and 'Millennium' are excellent options known for their disease resistance.

Size

Watermelon sizes can range from a few pounds to over 20 pounds. Larger melons may be impressive, but they also require more growing space and a longer maturity period. For New Hampshire gardens, opt for smaller to medium-sized varieties like 'Sugar Baby' or 'Crispy Red,' which typically weigh between 8 and 15 pounds.

Site Selection and Soil Preparation

Watermelons thrive in well-drained, nutrient-rich soil and full sun exposure. Proper site selection and soil preparation are essential for creating an ideal growing environment.

Watermelons require at least 6 to 8 hours of direct sunlight per day, so choose a planting location that receives ample sun exposure. In New Hampshire's cooler climate, consider using row covers or low tunnels to trap heat and extend the growing season.

Sun Exposure

Maximize sun exposure by orienting your planting rows in a north-south direction and selecting a site with minimal shade from trees or buildings. If necessary, prune or remove obstructions that could cast shadows over the growing area.

Soil Requirements

Watermelons prefer well-drained, sandy loam soil with a pH between 6.0 and 7.0. Poorly drained soils can lead to root rot and other issues, so avoid planting in low-lying areas or heavy clay soils.

Soil Amendments

Incorporate aged compost or well-rotted manure into the planting area to improve soil fertility and drainage. Apply a balanced, slow-release fertilizer following the manufacturer's instructions for optimal plant growth and fruit production.

Planting and Spacing

Proper planting techniques, including timing, depth, and spacing, are crucial for watermelon success in New Hampshire.

Watermelons are warm-season crops and should be planted after the last expected frost date in your area, typically in late May or early June. Start seeds indoors 3 to 4 weeks before the anticipated planting date to give your plants a head start.

Timing

In most parts of New Hampshire, the ideal planting window for watermelons is from mid-May to early June. This timing allows the plants to establish themselves before the hottest summer months and ensures sufficient time for fruit maturation before the first fall frosts.

Planting Depth and Spacing

Plant watermelon seeds or transplants at a depth of 1 to 2 inches, spacing them 2 to 3 feet apart in rows spaced 6 to 8 feet apart. This spacing allows for proper air circulation and access to sunlight, reducing the risk of disease and promoting optimal fruit development.

Transplanting

If starting with transplants, harden them off gradually by exposing them to outdoor conditions for a few hours each day, increasing the duration over a week or two. This process helps the plants adjust to the outdoor environment and reduces transplant shock.

When transplanting, handle the seedlings gently, and plant them at the same depth they were growing in their containers. Water the transplants immediately after planting to settle the soil and reduce transplant stress.

Caring for Watermelon Plants

Consistent care and maintenance are essential for producing a bountiful watermelon harvest in New Hampshire.

Watermelons have shallow root systems and require consistent moisture throughout the growing season. Provide approximately 1 to 2 inches of water per week, adjusting as needed based on rainfall and soil conditions.

Watering

Water deeply and slowly, aiming to moisten the soil to a depth of at least 6 inches. Avoid overhead watering, as wet foliage can promote fungal diseases. Instead, use soaker hoses or drip irrigation to deliver water directly to the root zone.

Mulching

Applying a 2 to 4-inch layer of organic mulch, such as straw or shredded leaves, around your watermelon plants can help retain soil moisture, suppress weeds, and regulate soil temperatures. Mulching also helps prevent soil from splashing onto the vines and fruit, reducing the risk of disease.

Pest and Disease Management

Watermelons are vulnerable to various pests and diseases, so monitoring and taking preventative measures are crucial. Common issues in New Hampshire include:

• Cucumber beetles: These pests can spread bacterial wilt and other diseases. Use row covers or apply insecticidal soap or neem oil to control them.
• Powdery mildew: A fungal disease that causes white, powdery growth on leaves. Improve air circulation and apply a fungicide if necessary.
• Fusarium wilt: A soil-borne fungus that causes wilting and plant death. Rotate crop locations and choose resistant varieties.

Regular scouting and prompt treatment can help prevent infestations from escalating.

Pollination

Watermelons require pollination by bees or other insects to produce fruit. Attract pollinators to your garden by planting a variety of flowering plants nearby, and avoid using broad-spectrum insecticides during bloom time.

If pollination is inadequate, you can hand-pollinate watermelon flowers by transferring pollen from male to female flowers using a small brush or cotton swab.

Common Watermelon Pests and DiseasesPrevention and Control Methods

Cucumber beetles	Row covers, insecticidal soap, neem oil
Powdery mildew	Improve air circulation, apply fungicide
Fusarium wilt	Crop rotation, resistant varieties

Harvesting and Storage

Knowing when to harvest and how to properly store your watermelons can help ensure you enjoy their sweet flavor at its peak.

Watermelons are typically ready to harvest 80 to 100 days after planting, depending on the variety. Keep an eye out for these signs of maturity:

Signs of Maturity

• The underside of the melon, where it rests on the ground, develops a creamy or yellow color (known as the "ground spot").
• The curly tendril nearest the fruit stem turns brown and dry.
• The rind develops a dull, matte appearance and becomes difficult to puncture with your fingernail.
• The melon develops a hollow sound when tapped lightly.

Harvesting Techniques

1. Use a sharp knife or pruning shears to cut the watermelon from the vine, leaving a few inches of stem attached.
2. Handle the fruit carefully to avoid bruising or puncturing the rind.
3. Avoid carrying watermelons by their stems, as this can cause them to break off.
4. Harvest watermelons in the morning or evening when temperatures are cooler to prevent them from overheating in the field.

Storage

Watermelons can be stored at room temperature for up to two weeks, but their shelf life can be extended by refrigerating them:

1. Store whole, uncut watermelons in the refrigerator at 50°F to 60°F.
2. Cut watermelons should be wrapped tightly in plastic wrap or placed in an airtight container and refrigerated.
3. For extended storage, watermelons can be frozen by cubing or pureeing the flesh and placing it in airtight containers or freezer bags.