Watermelons are everyone’s favourite summer treat! Large and sprawling, they grow similarly to other members of the cucurbit family, like pumpkins, squash, and cucumbers, but their flesh is much sweeter. With vibrant red flesh and a glossy green rind, watermelons are a refreshing snack in the heat. They can weigh anywhere from 2-3 kg to a massive 20 kg!
All About Watermelons
Watermelons love warm weather, which makes them more common in climates with long growing seasons. However, you can still grow them in colder areas by seeding indoors, buying young plants from a nursery, and choosing shorter-season varieties. Depending on the watermelon variety, it typically takes between 70 and 100 days from planting to harvest.
When To Plant Watermelon
Timing is the key when learning how to grow Watermelon. In cooler climates with short growing seasons, start watermelon seeds indoors 2 to 3 weeks before your last frost date. Transplant the seedlings into the garden about 2 weeks after that date or once the soil temperature reaches at least 65°F (18°C).
In warmer climates with long growing seasons, sow seeds directly outdoors 1 to 2 weeks after your last frost date. Make sure the soil has warmed to at least 65°F (18°C).
You can also purchase young watermelon plants from nurseries. Plant them once there’s no longer any risk of frost, as they are pretty tender. Check the local forecast and err on the side of caution. For an added boost, lay black plastic over the planting area to warm the soil further.
Tip: Starting with young plants can speed up your harvest by up to 2 weeks. It’s a great option for cooler climates.
How To Plant Watermelon
Watermelon can be grown from seeds or transplants. All you need to do is:
Soil Preparation
Watermelons prefer organic, rich, well-drained, sandy soils but can grow well in most soil types as long as drainage is good.
Select a sunny spot in your garden for planting. Before you start, conduct a soil test to determine the fertilizer needs and follow the recommendations provided. If fertilizer is needed, incorporate it into the top 6 inches of soil.
For compost, apply no more than 1 inch of well-composted organic matter per 100 square feet of garden area to enrich the soil naturally.
Planting
- Sow watermelon seeds 1/2 to 1 inch deep when planting outdoors or 1/4 to 1/2 inch deep when starting seeds indoors.
- Tip: Use larger seed-starting pots than usual to encourage root growth. Compostable pots are a great choice, as they can be cut away or planted directly into the garden, reducing the risk of damaging the seedlings’ delicate roots during transplanting.
- When direct seeding outdoors, plant 4 to 6 seeds per hill and thin them down to 2 or 3 seedlings as they grow.
Transplanting Seedlings
- Handle watermelon seedlings carefully during transplanting because the roots are fragile. Keep the soil intact while removing them from pots to prevent any disturbance.
- After transplanting, cover the plants with row covers to guard against pests. Be sure to remove the covers once male and female flowers appear, allowing pollinators to access the blooms.
How To Grow Watermelon
To Create a bushy, productive plant, follow the simple steps below on how to grow Watermelon.
Mulching
Black plastic mulch warms the soil, conserves water, and suppresses weeds. It’s especially effective for earlier planting and faster maturity, especially with transplants.
To use plastic mulch, lay it out over the planting area, secure the edges with soil, and cut holes for seeds or transplants. With plastic mulches and row covers, you can plant seeds or transplants 2–3 weeks before the last frost.
For organic mulches like grass clippings, straw, or newspapers, wait until the soil warms to at least 75°F. Both plastic and organic mulches effectively conserve water and control weeds for healthy growth.
Row Covers
Row covers are great for enhancing growth and encouraging earlier harvests. Hotcaps, plastic tunnels, fabric covers, and similar devices protect seedlings and transplants from chilly air temperatures.
Use a thermometer to monitor the temperature under the covers. Ventilate the plants when air temperatures rise above 80°F, and remove the covers entirely when temperatures exceed 90°F or when the plants begin to flower. Once the weather stabilizes, remove the covers to allow the plants to grow naturally.
Watering
Watering is essential in learning how to grow watermelons. Melon plants need 1 to 2 inches of water per week during their growth, blooming, and fruit-setting stages.
Keep the soil consistently moist but not waterlogged. Water at the base of the vines in the morning. Avoid wetting the leaves or using overhead watering. As the fruit begins to grow, reduce watering.
Fertilizing
If you decide to fertilize, choose one with a higher nitrogen content initially to promote healthy leaf and vine growth. Once the plants start flowering, switch to a fertilizer with lower nitrogen levels to focus on encouraging blooms and fruit development. A seaweed-based fertilizer works excellent for this purpose.
Harvesting and Storing
Watermelons typically ripen over two weeks. Once one melon is ripe, the others will soon follow. About a week before ripening, water only as needed to keep the vines from wilting. Withholding water at this stage concentrates sugars in the fruit and enhances its sweetness. Too much water can reduce sweetness.
You can tell a watermelon is ripe by its skin colour. The rind shifts from bright to dull green, and the part touching the soil changes from greenish-white or straw yellow to a rich, creamy yellow. Another method is tapping the skin and listening for a low-pitched thud. Practice by tapping a few unripened fruits. Those that aren’t ripe will produce a high-pitched, tinny sound.
Uncut watermelons can be stored for about 10 days, while cut pieces should be wrapped tightly in plastic and stored in the refrigerator for up to 4 days.
