How to Grow Watermelon in Containers

Can You Grow Watermelons in a Container?

Let's start with the obvious. Can you grow watermelons in a container? Yes!

Watermelons can grow well in a container if you choose the right variety and give them proper care. These sprawling vines typically consume a lot of space in a traditional garden, but you can grow them with the proper-sized gardening container, some trellising, and consistent watering.

Container-grown watermelons have advantages over in-ground planting. For example, a box planter with good potting soil and proper drainage holes helps prevent soil-borne diseases. It also gives you more control over nutrients. Plus, container gardening makes protecting plants from weeds and certain pests easier.

Some Challenges of Container-Grown Watermelons

OK. We said you could grow watermelons in containers, but it can be more challenging than growing other produce like tomatoes or peppers.

Watermelons require warm temperatures, plenty of space, and consistent care to thrive. Here are five challenges you might face when growing watermelons in containers:

1. Watermelons Need Lots of Space

Even compact or bush varieties have long vines that can stretch several feet. Without space, you’ll need to train them onto a trellis, which requires extra support for the heavy fruit.

2. Pollination Can Be a Challenge

Watermelon plants produce both male and female flowers and require pollination for fruit to develop. Bees typically handle that effort. But without a pollination source, you may need to hand-pollinate using a small brush to transfer pollen between flowers.

3. Watering Must Be Just Right

• Too much water? It can cause root rot or split the fruit.
• Too little water? The melons won’t develop properly.
• Inconsistent watering? It can lead to bland or cracked fruit.

The good news is that you can address watering concerns with a self-watering planter box. EarthBox, for example, offers a self-irrigated planter that handles the watering for you. Use the fill tube to add water to the planter's reservoir, and your plants will drink when ready.

Your plants will enjoy a consistent water source, keeping them thriving. Simply make sure the reservoir stays filled.

4. Watermelons Are Heavy Feeders

Because watermelons grow rapidly and produce large fruit, they require constant nutrients. If the soil lacks nitrogen early on, the plant won’t grow well. If it lacks potassium later, the fruit won’t be as sweet. Regular feeding with the right fertilizer is essential.

5. Pests and Diseases Can Cause Problems

Container gardening reduces some risks, but aphids, spider mites, and cucumber beetles still pose a threat. Fungal diseases like powdery mildew can also develop with poor airflow. To prevent issues:

• Space out plants for better air circulation.
• Check leaves regularly for signs of pests or disease.
• Use natural pest control methods like neem oil if needed.

If these concerns don't bother you, then it’s time to learn how to successfully grow watermelons in pots. Follow these steps, and you can enjoy sweet, homegrown watermelon wherever you live!

Best Watermelon Varieties for Containers

Not all watermelon types are suited for pots or planter boxes. Look for smaller or bush varieties that require less space but still produce delicious fruit.

• ‘Sugar Baby’ – A classic small watermelon with sweet, red flesh.
• ‘Bush Sugar Baby’ – A compact version, perfect for smaller spaces.
• ‘Golden Midget’ – A fast-growing variety with golden-yellow skin.
• ‘Mini Love’ – Early maturing and disease-resistant.

These varieties thrive in containers better than traditional sprawling watermelon plants.

What's the Best Size for a Watermelon Pot?

Watermelon plants need a sizeable container with at least 5 gallons of soil per plant, but bigger is better. Ideally, a 10–15 gallon planter box or pot is best to accommodate their deep roots and sprawling vines.

You can use large plastic pots, fabric grow bags, and half-barrel planters. However, make sure the container has drainage holes to prevent water from pooling at the bottom, which can lead to root rot.

You'll also want to place your container or planting box where your plants will get 6-8 hours of sunlight.

How Much Space Do Watermelons Need?

While watermelons can adapt to container growing, they still require ample space for their sprawling vines, which can grow 6 to 10 feet long. That can translate to as much as 20 square feet of space.

If you don't have enough ground space, you can train them to grow vertically on a trellis. If you want to let them spread out naturally, place your container in an open area. That will allow the vines to trail over a patio or balcony floor without tangling. The trailing vines can even act as a privacy screen.

How Many Watermelons Can You Plant Per Container?

For best results, plant only one watermelon plant per large pot or planter box to allow enough room for roots and vines. If using a considerably larger container (20 gallons or more), you may be able to plant two.

Planting is simple by following these steps:

1. Potting soil: Avoid garden soil, which can be too compact. Watermelons prefer a loamy soil (more on that in a minute).
2. Fertilizer: Watermelons are heavy feeders. Start with a slow-release granular mix. During initial growth, go a little heavier on nitrogen for leaf growth. Once flowers appear, support fruit development with a heavier phosphorous and potassium mix. Add fertilizer at least every two weeks.
3. Seeds or seedlings: Sow seeds directly in the soil or transplant young plants after the last frost.
4. Support: If you don't have space for sprawling vines, use a trellis to train vines to grow vertically. Support fruit growing with cloth or pantyhose slings to prevent them from breaking off. EarthBox offers a vertical gardening bundle that's perfect for vining plants.
5. Mulch: Add plenty of mulch to your planter box to retain moisture and regulate temperature.

What Kind of Soil Does Watermelon Like?

We mentioned soil, but let's dig a bit deeper. Watermelons grow best in loose, well-draining potting soil rich in organic matter. Avoid using dense garden soil, which can compact too easily in containers.

The best soil mix includes:

• A lightweight potting mix with peat, perlite, or coco coir.
• Lots of organic compost for added nutrients. When planting, use 50% potting mix with 50% compost.
• A slightly acidic to neutral pH (6.0–6.8) for optimal growth.

What Is the Best Fertilizer for Watermelons?

Remember, watermelons are heavy feeders requiring plenty of nutrients throughout their growing cycle. The best fertilizer approach includes:

• A balanced fertilizer (10-10-10 or 12-12-12) at planting to promote overall growth.
• Use a phosphorus-rich fertilizer (5-10-10) during flowering to encourage strong roots and blossoms.
• Use a potassium-rich fertilizer (0-0-12 or 3-12-12) as the fruits develop to enhance sweetness and water retention.

Companion Planting: What to Avoid Growing Next to Watermelons

Certain plants can either help or hinder watermelon growth. Avoid planting watermelons near:

• Potatoes compete for nutrients.
• Cucumbers & squash increase the risk of shared pests and diseases.
• Pumpkins can cross-pollinate and produce odd fruit.

Good companions for watermelon include basil, marigolds, and radishes, which help deter pests.

How Long Does It Take for a Watermelon to Grow?

Watermelon growth depends on the variety, but most take 70–90 days from planting to harvest. Mini or bush varieties may mature slightly earlier, around 65–75 days. Warmer temperatures and proper care can help speed up growth.

Do You Only Get One Watermelon Per Plant?

No, a healthy watermelon plant can produce multiple melons. On average, expect 2–4 melons per plant in a container, depending on the variety and growing conditions.

How to Make Watermelon Sweeter

How well you care for your plants impacts how sweet and juicy your watermelons are. For the sweetest fruit, pay attention to these items:

1. Sun: More sun exposure equals sweeter fruit.
2. Water: Don’t overwater near harvest time, as too much water can dilute the sweetness.
3. Fertilizer: Add a potassium-rich fertilizer to enhance the natural sugars in the fruit.
4. Harvest: A ripe watermelon will have a yellow underside and a dried tendril near the stem.

How to Tell When a Watermelon Is Ripe

One of the most complex parts of growing watermelon is knowing when to pick it. If you harvest too soon, it won’t be sweet. It might overripen and lose its crisp texture if you wait too long. Here's a trick to know when to harvest: the two-finger rule.

A ripe watermelon has darker green stripes about the width of two fingers. Find your perfect watermelon by holding your index and middle fingers together and place them lengthwise along the watermelon's stripes. If they fit between the darker green area and the white stripes, it's ready for harvest.

Other ways to check ripeness:

• Ground Spot Color: The part of the melon that touches the ground should turn yellow, not white.
• Knock Test: A ripe watermelon sounds hollow when tapped.
• Skin Appearance: A dull, non-shiny surface means the fruit is fully mature.

EarthBox Removes the Challenge of Growing Watermelons in Containers

Growing watermelons in a planter box is a great way to enjoy fresh fruit, even if you don’t have a large garden. EarthBox can help ensure your success. We've been helping home gardeners grow fresh produce for over 30 years.

Our award-winning planting boxes and growing system let you grow watermelon, tomatoes, peppers, herbs, and other fresh produce. It helps gardeners with even the smallest spaces enjoy container gardening success.