10 Must-Know Tips for Growing Sweeter, Juicier Watermelons

A perfectly ripe watermelon should be sweet, juicy, and packed with a fruity flavor that brings to mind backyard barbecues and summertime picnics. But if watermelons are harvested too early or grown in less-than-ideal conditions, they may not develop the desired sugary-sweet flavor.

To ensure your harvest meets your standards, these tips walk you through everything you need to know to grow sweeter watermelons, from seed to harvest.

1. Choose Sweeter Varieties

Some watermelon varieties are known to be sweeter than others, and if it’s sweetness you’re after, these are the watermelons to grow. Varieties like ‘Charleston Grey,’ ‘Bradford,’ ‘Crimson Sweet,’ and ‘Sultan’ are particularly esteemed for their high sugar content, but there are other tasty types of watermelons to try. Just keep in mind that to produce fruit, seedless watermelons will need to be planted alongside seeded varieties (referred to as pollenizers or watermelon pollinator plants).

2. Pick a Sunny Location

The most important factor that determines how sweet watermelons will be when harvested is the amount of heat and sun the plants are exposed to during the growing season. Long periods of cool and cloudy weather make watermelons less sweet, while lots of hot sun will cause the plants to produce more sugars and more flavor.

Of course, gardeners don’t have much control over the weather. But you can set your watermelon plants up for success by growing them in full sun locations that receive at least eight hours of direct light per day. Covering the soil with black plastic sheeting also makes the soil warm up faster and may be helpful if you’re experiencing a cooler-than-average summer.

3. Enhance the Soil

Some plants handle nutrient-poor soil, but watermelons are heavy feeders that need rich, well-draining, and slightly acidic soil to grow well. Testing your soil and mixing a few inches of compost into the area before planting is a must if you want watermelons to thrive. You can also experiment with growing melons in DIY melon pits filled with food scraps and other organic waste that will fuel the rapid growth of watermelon vines.

4. Plant at the Right Time

Watermelons are heat-loving plants that don’t tolerate cold weather and should only be planted outdoors after the risk of frost has passed. Still, it’s important not to sow watermelon seeds too late. These plants need to do most of their growing during the hottest part of summer to produce the sweetest fruit.

Watermelons take 85 to 95 days to maturity. If your growing season does not offer at least three months of warm weather (including warm nights above 60°F), you may need to start the seeds indoors. In a warmer climate, sow watermelon seeds outdoors about one to two weeks after the risk of frost has passed.

5. Water Well

With a name like “watermelon,” it’s no surprise that watermelon plants need regular watering and should be provided with about 1 to 2 inches of water per week.

Once your plants set fruit, it’s best to dial back on watering and to withhold all water two weeks before you intend to harvest your plants. Watering too much when the fruit is developing tends to dilute the sugars in watermelons and make them less sweet.

6. Fertilize Regularly

Growing watermelons in soil that’s been enriched with compost or a melon pit makes your plants support healthy plant growth, but it is not enough. Watermelons are such heavy feeders that they will need extra fertilizer as they grow. Feed watermelons about once every six weeks with a granular fertilizer, or every two weeks with a liquid fertilizer. Note that application rates vary depending on the product; always read the label instructions.

7.  Prevent Fungal Issues

Powdery mildew and other fungal plant diseases often occur when the air gets humid and watermelon plants are grown too closely together. Although these issues are rarely fatal to watermelon vines, they potentially make plants less productive and lower the quality of the fruit.

Following proper spacing guidelines and watering watermelons at the soil line instead of overhead minimizes some fungal problems. However, you may also want to preventatively treat watermelon leaves with a weekly application of milk spray if mildew is a recurring problem in your garden every season.

8. Prune Wisely

For the most part, it’s best to avoid pruning watermelon vines as removing leaves interferes with the plant’s ability to photosynthesize and produce the sugars that make watermelons sweet. However, pruning some of the extra flowers and fruit off your plants channels the plant’s energy into making the watermelons that remain a little sweeter.

Wait until your plants have three to four watermelons developing on a vine, then prune away any flowers and fruit that develop on the vine afterwards.

9. Watch for Pests

Just like mildew issues, pests stress watermelon plants and make it harder for the vines to produce big and tasty fruit. Keep an eye on your plants to detect any pest issues early. To control aphids and spider mites, spray the plant with a strong blast of water from the hose, or use insecticidal soap.

A natural way of pest control is to use flowers and scented herbs as companion plants for watermelons. They repel pests and attract beneficial insects that feed on them. As a bonus, many flowering companion plants also attract pollinators and help to ensure your watermelon vines set fruit.

10. Know When to Harvest

Pick watermelons when they’re perfectly ripe to get the best flavor, as the fruit doesn’t continue to ripen off the vine. You’ll know your watermelons are ripe and ready when:

• Their rinds become dull.
• The bottom of the fruit turns from white to yellow.
• The vines begin to brown.
• The watermelon produces a dull thunking sound if you tap on it with your knuckles.

When all these boxes are checked, the watermelon is ready to be harvested. Cut it off the vine with a sharp knife and eat it as soon as you can for the best and sweetest flavor.