How to Grow Watermelon in Washington

Choosing the Right Watermelon Variety

The first step in growing watermelons in Washington is choosing varieties that are well-suited to the state’s climate and growing season. Washington’s summers are generally warm and dry, but the growing season can be shorter than in more southern regions. To ensure a successful harvest, it’s important to select varieties that mature within the available growing period. Here are some recommended watermelon varieties for Washington:

VarietyDescription

Sugar Baby	An early-maturing variety that produces small, round fruits (6-10 lbs) with crisp, sweet flesh. Well-suited for cooler climates.
Crimson Sweet	A popular variety known for its large size (16-25 lbs), deep red flesh, and excellent flavor. Requires a longer growing season.
Charleston Gray	An heirloom variety with light green striped rind and sweet, red flesh. Adapts well to various climates and produces fruits around 25 lbs.
Yellow Doll	A unique variety with yellow flesh and a sweet, honey-like flavor. Produces small fruits (5-10 lbs) and performs well in cooler regions.

Preparing the Soil

Watermelons thrive in well-drained, nutrient-rich soil with a pH range of 6.0 to 6.8. To prepare the soil for planting, follow these steps:

• Test your soil’s pH level and adjust it if necessary by adding lime (to raise pH) or sulfur (to lower pH).
• Incorporate plenty of organic matter, such as compost or aged manure, into the soil to improve drainage and fertility.
• Remove any weeds, rocks, or debris from the planting area.
• Create raised beds or hills to improve soil drainage and warmth, which is essential for watermelon growth.

Planting and Spacing

The optimal time for planting watermelon seeds or transplants in Washington is typically between late May and early June, once the soil has warmed up to at least 70°F (21°C). Follow these steps for successful planting:

1. If planting seeds directly, sow them 1 inch deep and 2-3 feet apart in hills or rows, with 6-8 feet between rows.
2. If using transplants, space them 2-3 feet apart in rows, with 6-8 feet between rows.
3. Apply a layer of mulch around the plants to conserve moisture and suppress weeds.
4. Use row covers or plastic tunnels to protect young plants from cooler temperatures and pests.

Water and Fertilizer Requirements

Watermelons require consistent moisture throughout the growing season, especially during fruit development. Here are some key points regarding water and fertilizer requirements:

• Water deeply and regularly, providing about 1-2 inches of water per week, depending on rainfall and soil conditions.
• Avoid overhead watering, as it can promote fungal diseases. Instead, use drip irrigation or furrow irrigation methods.
• Apply a balanced fertilizer, such as 10-10-10, at the time of planting and again when the vines begin to run.
• Supplement with additional nitrogen fertilizer once the fruits start developing.

Watering Techniques

Proper watering is crucial for watermelon growth and fruit production. Here are two recommended watering techniques:

1. Drip Irrigation: This method delivers water directly to the root zone, minimizing water loss and reducing the risk of fungal diseases. Drip irrigation systems can be easily set up and automated.
2. Furrow Irrigation: Create shallow furrows or trenches between rows of watermelon plants. Water is then channeled through these furrows, allowing it to slowly seep into the root zone. This method can be labor-intensive but is effective for larger plantings.

Fertilizing Schedule

To ensure optimal growth and fruit production, follow this fertilizing schedule for watermelons:

• At planting: Apply a balanced fertilizer, such as 10-10-10, at the rate recommended on the package.
• When vines begin to run: Side-dress with additional nitrogen fertilizer, such as ammonium nitrate or urea, at a rate of 1/4 to 1/2 pound per 100 square feet.
• Fruit development stage: Apply another side-dressing of nitrogen fertilizer, using the same rate as before.

Pest and Disease Management

Like many cucurbit crops, watermelons are susceptible to various pests and diseases that can significantly impact their growth and yield. Here are some common issues to be aware of and their respective control measures:

Pest/DiseaseControl Measures

Aphids	Use insecticidal soaps, neem oil, or introduce beneficial insects like ladybugs.
Cucumber Beetles	Apply row covers, use sticky traps, or treat with pyrethrin-based insecticides.
Squash Bugs	Remove egg clusters by hand, use insecticidal soap, or apply neem oil.
Fusarium Wilt	Plant resistant varieties, practice crop rotation, and improve soil drainage.
Anthracnose	Apply fungicides, remove infected plant materials, and improve air circulation.
Gummy Stem Blight	Use fungicides, maintain good airflow, and avoid overhead watering.

Insect Pests

Some common insect pests that can affect watermelon plants in Washington include:

• Aphids: These small, pear-shaped insects can transmit viruses and cause stunted growth. Control measures include insecticidal soaps, neem oil, or introducing beneficial insects like ladybugs.
• Cucumber Beetles: These yellow or striped beetles can damage leaves, stems, and fruits. Use row covers, sticky traps, or pyrethrin-based insecticides to manage them.
• Squash Bugs: These brown, shield-shaped bugs can cause wilting and stunted growth. Remove egg clusters by hand, use insecticidal soap, or apply neem oil for control.

Plant Diseases

Watermelons are susceptible to several fungal and bacterial diseases, including:

• Fusarium Wilt: This soil-borne disease causes wilting and stunted growth. Plant resistant varieties, practice crop rotation, and improve soil drainage to prevent it.
• Anthracnose: This fungal disease causes lesions on leaves, stems, and fruits. Apply fungicides, remove infected plant materials, and improve air circulation to manage it.
• Gummy Stem Blight: This disease causes stem and leaf lesions, leading to wilting and fruit rot. Use fungicides, maintain good airflow, and avoid overhead watering to control it.

Harvesting and Storage

Knowing when to harvest watermelons is crucial to ensure optimal flavor and quality. Here are some tips for successful harvesting and storage:

Harvesting Tips

• Check the tendril (curly stem) closest to the fruit – when it turns brown and dries up, the watermelon is likely ripe.
• Look for a yellow or creamy underside where the watermelon rests on the ground.
• Give the watermelon a gentle tap – a dull, hollow sound indicates ripeness.
• Use a sharp knife or pruners to cut the stem, leaving a short stub attached to the fruit.

Storage Methods

Proper storage is essential to extend the shelf life of freshly harvested watermelons:

• Store watermelons at a cool temperature, around 55°F (13°C), with a relative humidity of 85-90%.
• Avoid storing watermelons in direct sunlight or near ripening fruits like bananas or tomatoes, as they release ethylene gas that can cause premature spoilage.
• Whole, uncut watermelons can typically be stored for 2-3 weeks, while cut watermelons should be consumed within 3-5 days.

Conclusion

Growing watermelons in Washington may require some extra effort, but the rewards of harvesting these sweet, juicy fruits make it all worthwhile. By following the steps outlined in this guide, from selecting the right variety to implementing proper planting, care, and harvesting techniques, you can increase your chances of a successful watermelon crop in Washington. With patience, dedication, and a little bit of watermelon-growing know-how, you can enjoy the delicious taste of homegrown watermelons throughout the summer months.