How to Grow Watermelon in Gardening Containers

Growing a Summertime Staple in Planting Boxes

Growing your watermelons might seem intimidating, but growing watermelon in gardening containers is easy. Here are the benefits of growing watermelons in planting boxes:

1. Watermelons require a lot of water—several gallons per day. So, look for gardening containers with at least a three-gallon water reservior.
2. Watermelon plants hate wet feet and waterlogged roots—such will negatively impact your harvest. By using a well-aerated growing medium in your planting box, such as one of the potting mixes mentioned on our Approved Growing Media page, the roots can draw water as needed without overly saturating the soil.
3. Watermelons require warm temperatures and plenty of sunshine to grow healthy—they are happiest in full sun with daytime temperatures above 80 degrees, and evenings that don’t dip below mid-50s. If you put your gardening containers on casters, you can easily move your system around to provide your plants with optimal sunlight. Don’t worry if your local temperatures are not quite there yet – the EarthBox® Frost Cover can help growers in cooler climates get an early start; or you can wheel your gardening boxes inside at night using the Caster Kit! If you’re unsure of your frost-free dates, check your USDA Zone before planting.
4. Watermelons need support—Another key to success in growing watermelon is using some type of vertical gardening container. The EarthBox® 7’ Staking System is stable and tall enough to offer the vertical support your vining plants need! Easily guide the watermelon vines to the trellis net and they will begin training up the net themselves. Once the fruit starts to develop and grows to the size of a baseball, you should create a sling or hammock to support it on the vine, so it does not drop off from its own weight. The best materials for making a hammock are strips of t-shirts and sheets, cheesecloth, pantyhose, or mesh onion bags. Simply tie one end of the sling to the trellis net next to the fruit, bring the cloth under the fruit, and tie the other end to another part of the trellis net. Check daily to ensure the fruit has not fallen off its sling.
5. Follow our tried and true guidance—In our years, we’ve grown A LOT of watermelons. Trust us and follow our instruction manual, planting chart, and growing guide so you can grow A LOT of watermelons too!
   (Place 4 watermelon seedlings in the EarthBox Original gardening system in a staggered pattern to give plants space to climb.)

Best Varieties to Grow in Planting Boxes

With the potential to develop massive vines and take over almost 150 square feet of space, watermelons don’t always make the best neighbors to other plants in the garden. This makes choosing a smaller watermelon variety for your container garden crucial to getting started. The best varieties will produce melons weighing 12 pounds or less, and often they will have terms that denote their size, like “baby,” in the name. You’ll need 4 watermelon plants to get started. You can choose all one variety, or mix it up and plant several different ones.

Recommended watermelon varieties for gardening containers:

• Sugar Baby
• Yellow Petite
• Moon & Stars
• Crimson Sweet
• Blacktail Mountain
• Moonbeam
• Golden Midget
• Sangria (this is a larger variety, but one we have successfully grown ourselves in our EarthBox company garden!)

Common Watermelon Pests and Problems

Be proactive when you plant by keeping watch for aphids, cucumber beetles, and squash vine borers—they can cause wilting and browning of leaves, stunted growth, and can even spread bacterial wilt. Beneficial insects like ladybugs and green lacewings will eat their eggs; and insecticides like neem oil will help eliminate the adults.

Fungal diseases are also very common in cucurbits. One such disease, fusarium wilt, will cause infected plants to wilt and turn yellow. Fungicides can slow the spread of this disease, but once infected, there is no way to completely stop it. You should remove and destroy any infected plants, do not compost them. Watermelons can also develop Blossom End Rot (BER), which can be easily treated and corrected. You can learn more about BER from our article, All About Blossom End Rot.

How to Know When to Pick Watermelon

When your watermelon is ready to harvest will depend on which variety you choose to grow. On average, you should expect to harvest approximately 60 to 90 days after planting, or about 45 days after you see fruit develop. Look for visual cues to determine when the fruit is ready to be picked, such as the color of the rind and the vine’s tendrils. The rind will change from bright to dull green as it ripens, and its belly will turn from white to yellow. The tendrils will also begin turning yellow, eventually to brown. You can also test for ripeness by the sound made when tapping on the melon. Under-ripe fruit will make a higher pitched sound, and the pitch will lower to a dull thud as the melon ripens. Ripening on the vine takes about two weeks, so as you start noticing these changes in the fruit, you can decide if you want to withhold water for the last week before the melon is fully ripe. Withholding water helps concentrate the sugars, which is what makes the melons so sweet. Too much water during the ripening phase can lead to bland, tasteless watermelons.

Once your fruit is ready, you can cut it right off the vine! Your watermelons will keep for two to three weeks on the counter, and even longer if you store them in the refrigerator. You can also freeze some of the fruit for use in slushies to help you stay cool in the heat!

Have you ever grown watermelons in your EarthBox? Share your favorite watermelon varieties in the comments below!