Watermelons are a summertime favorite, known for their sweet, juicy flesh that’s perfect for hot days. Growing watermelons from seed is a rewarding project that allows you to enjoy fresh, homegrown fruit right from your garden. While these sprawling plants need space, warmth, and consistent care, they’re not as difficult to grow as they might seem. This guide will take you through the process of growing watermelons from seed, from selecting the right variety to harvesting your delicious fruits.

Why Grow Watermelons from Seed?

Starting watermelons from seed has several advantages:

  1. Variety Selection: Growing from seed gives you access to a wide range of watermelon varieties, including heirloom, seedless, and mini types that may not be available as transplants.
  2. Cost Savings: Seeds are cheaper than buying established plants, especially if you plan to grow multiple watermelon plants.
  3. Control Over Growing Conditions: Starting from seed allows you to manage the growth environment from the very beginning, ensuring healthy and vigorous plants.

Choosing the Right Watermelon Variety

Before you start, it’s important to choose a variety that suits your climate, space, and taste preferences. Watermelons are typically categorized by their size, sweetness, and growing duration:

  1. Icebox Varieties: Small, compact watermelons like ‘Sugar Baby’ and ‘Golden Midget’ are ideal for smaller gardens and take less time to mature. They typically weigh between 6 and 15 pounds.
  2. Picnic Varieties: Larger watermelons like ‘Crimson Sweet’ and ‘Charleston Gray’ are traditional types that produce fruit weighing 20-40 pounds or more. They require more space and a longer growing season.
  3. Seedless Varieties: Varieties like ‘Triple Crown’ and ‘Millionaire’ are hybrid types that produce seedless fruit. They require a pollinator variety to set fruit.
  4. Novelty Varieties: Heirloom and specialty varieties like ‘Moon and Stars’ or yellow-fleshed watermelons offer unique colors, flavors, and patterns.

When to Start Watermelon Seeds

Watermelons need a long, warm growing season. They thrive in temperatures between 70°F and 90°F (21°C to 32°C) and are sensitive to frost. In cooler climates, it’s essential to start seeds indoors to give your plants a head start.

  • Indoor Seed Starting: In cooler regions, start watermelon seeds indoors 4-6 weeks before the last expected frost date. This helps the seedlings establish before transplanting them outdoors once the soil warms up.
  • Direct Sowing Outdoors: In warmer climates, where the growing season is long and frost-free, you can sow watermelon seeds directly in the garden after all danger of frost has passed and the soil has warmed to at least 70°F (21°C).

Preparing the Soil

Watermelons grow best in loose, well-drained soil that’s rich in organic matter. The ideal pH range is between 6.0 and 6.8. Here’s how to prepare your garden bed:

  1. Choose a Sunny Location: Watermelons need full sun, which means at least 8-10 hours of direct sunlight per day.
  2. Soil Preparation: Before planting, amend the soil with plenty of compost or well-rotted manure to improve fertility and drainage. Watermelons are heavy feeders, so providing rich soil from the start will give them a strong foundation.
  3. Raised Mounds or Hills: Watermelons are often planted in mounds or hills to ensure good drainage and to keep the soil warm. Create mounds that are 3-6 feet apart, depending on the variety, and 8-12 inches high. Work in compost or a balanced fertilizer into each mound.

Planting Watermelon Seeds

Once your soil is ready, it’s time to plant the seeds:

  1. Sowing Indoors: Plant seeds in biodegradable pots or seed trays filled with seed-starting mix. Sow seeds about 1/2 inch deep and keep them in a warm place. Maintain consistent moisture and provide 12-16 hours of light daily using grow lights if needed. Watermelon seeds usually germinate within 7-10 days.

  2. Transplanting Seedlings: Once the seedlings have at least two true leaves and the outdoor temperatures are consistently warm, harden them off by gradually exposing them to outdoor conditions over a week. Transplant them to the garden, placing them in the center of each prepared mound or hill.

  3. Direct Sowing Outdoors: If sowing directly, plant 3-4 seeds per hill, about 1 inch deep. Once the seedlings emerge, thin them to the strongest two or three plants.

Watermelon Plant Care

Watermelons require consistent care throughout the growing season. Here’s how to give them what they need:

  1. Watering: Watermelons need regular, deep watering, especially during flowering and fruit set. However, be careful not to overwater, as soggy soil can lead to root rot. Aim to keep the soil consistently moist but not waterlogged. Once fruits start to mature, reduce watering to improve the sweetness of the melons.

  2. Mulching: Mulching around the base of the plants helps retain soil moisture, suppress weeds, and keep the fruit clean. Use straw, hay, or black plastic mulch. Black plastic also warms the soil, which can be beneficial in cooler climates.

  3. Fertilizing: Watermelons are heavy feeders. Start with a balanced fertilizer (such as 10-10-10) when preparing the soil. Once the vines begin to spread, switch to a fertilizer that is higher in phosphorus and potassium to support flowering and fruiting. Avoid too much nitrogen, as it can lead to excessive vine growth at the expense of fruit production.

  4. Weeding: Keep the garden bed free of weeds, especially early in the season when watermelon plants are establishing. Hand-pulling weeds is best to avoid disturbing the shallow roots of the watermelon plants.

  5. Supporting the Vines: Watermelon vines can sprawl over large areas, often growing 10-20 feet long. If space is limited, consider using a trellis or vertical support system for smaller varieties. Use slings made of cloth to support the heavy fruit as they develop on the trellis.

Pollination and Fruit Development

Watermelons produce separate male and female flowers on the same plant. Pollination is crucial for fruit set, and it’s primarily done by bees. Encourage pollinators by planting bee-friendly flowers nearby. You can also hand-pollinate by transferring pollen from the male flowers to the female flowers using a small brush.

  • Male Flowers: Appear first and have a straight stem.
  • Female Flowers: Appear later and have a small swelling at the base, which is the developing fruit.

Common Pests and Problems

Watermelons can be affected by a variety of pests and diseases. Here are some common issues to watch for:

  1. Pests: Aphids, cucumber beetles, and squash bugs are common pests. Use organic insecticidal soap or neem oil for control. Row covers can protect young plants but should be removed once flowering begins to allow for pollination.
  2. Diseases: Fungal diseases like powdery mildew, downy mildew, and anthracnose can affect watermelon plants. Ensure good air circulation, avoid overhead watering, and use disease-resistant varieties when possible.
  3. Blossom-End Rot: Caused by calcium deficiency, this condition results in dark, sunken spots on the fruit. Ensure consistent watering and add calcium supplements to the soil if needed.

Harvesting Watermelons

Knowing when to harvest watermelons is key to enjoying their peak sweetness. Unlike other fruits, watermelons do not continue to ripen after being picked, so timing is crucial.

  1. Days to Maturity: Check the seed packet for the variety’s expected maturity time, usually between 70 and 100 days from planting.

  2. Color and Sound: The bottom of the watermelon (where it touches the ground) should change from white to a creamy yellow color when it’s ripe. Additionally, the skin should be dull rather than shiny. Some gardeners use the “thump” test—when you tap the fruit, it should produce a deep, hollow sound.

  3. Tendrils: Near the stem where the watermelon is attached to the vine, look for a curly tendril. When this tendril turns brown and dries out, it’s a good indicator that the watermelon is ready to harvest.

Storing and Enjoying Your Watermelons

Once harvested, watermelons can be stored at room temperature for a week or two. For longer storage, keep them in a cool place. Once cut, refrigerate the watermelon and cover it with plastic wrap to keep it fresh.

Enjoy your homegrown watermelons in a variety of ways: fresh slices, fruit salads, smoothies, or even grilled! The taste of a watermelon grown in your own garden is unbeatable.

Conclusion

Growing watermelons from seed is a rewarding endeavor that, with the right care and attention, results in delicious, juicy fruits. From selecting the right variety to nurturing the vines and harvesting at just the right moment, every step of the process is filled with the promise of sweet success. Whether you have a large garden or a small patch, with the right variety and a bit of effort, you can enjoy the taste of summer straight from your backyard. Happy gardening!