How to Grow Watermelon in Pots – 8 Tips to Get Sweet, Juicy Fruits in Small Spaces
The steps to success from planting to harvesting
I currently have a watermelon plant growing in my greenhouse. Am I crazy, trying to grow a watermelon in a container in zone 8 (the north-west of the UK)? Maybe I am, but god loves a trier. It may be difficult, but you can grow watermelon in pots, provided you make the right choices.
Those decisions include picking the right variety, container, and soil. Then there is the need to give the plants the right amount of sun, water, and nutrients. It is tricky, but not impossible if you are willing to put in the effort.
Here I take a look at some vital factors you must consider if you want to grow watermelon in a container, whether indoors or outdoors. Who knows if I will get a crop of juicy, sweet fruits from my watermelon, but I am up for the challenge.
1. Pick the Right Type
Watermelon plants can grow up to 10 feet. In reality, that is too big for containers. If you want to grow watermelon in pots, don’t complicate things. You can make life easier on yourself by growing compact and bush varieties.
These types are more manageable, and the fruit is just as tasty and juicy as that of the larger types. The vines grow shorter – often reaching 2 or 3 feet rather than 10 – and you can end up with a few good-sized watermelons per plant to pick.
The likes of ‘Sugar Baby’, ‘Bush Sugar Baby’ or ‘Golden Midget’ are perfect compact varieties of watermelon that thrive in containers.
Get ‘Sugar Baby’ watermelon seeds at True Leaf Market
Get ‘Bush Sugar Baby’ watermelon seeds at Burpee
Get ‘Golden Midget’ watermelon seeds at True Leaf Market
2. Use a Large Pot
When you decide to grow watermelon in pots, you need to pick a large container to have any chance of success. This is crucial as watermelons have extensive root systems and need room to develop. Pick a pot that is too small and the plant will get root-bound and stressed, plus you’ll end up watering more.
For the best chances of success, a dwarf or compact watermelon variety needs at least a 10-gallon pot. But to be safe, aim for 15 to 20 gallons. It should ideally be 18 to 24 inches deep and wide. This gives the roots ample space to grow and helps make maintenance easier.
The other non-negotiable is drainage holes. The pot needs to drain excess water. Otherwise, the plant will sulk and can succumb to root rot sitting in sodden soil for long periods.
Most pots should come with drainage holes, but it is best practise to check. Thankfully, it is not difficult to add drainage holes to planters to give watermelons the drainage they need.
You can use large pots (like these 15-gallon nursery pots at Amazon) or grow bags (you can also get 15-gallon grow bags at Amazon).
3. Fill the Pot With Fertile, Well-Draining Soil
Watermelons are heavy feeders, making it important to use the right soil in the containers. For a rich mix, combine a quality potting soil with compost at an 80:20 ratio.
This blend will drain well. It will also provide essential nutrients so the watermelon grows healthily in the container.
This organic potting mix at Walmart is a great option. If you don’t have any homemade compost to mix with it, you can buy bags. For example, you can get a 10lb bag of organic compost at Amazon.
4. Plant Your Watermelon
There are two options for planting the watermelon into the soil. You can sow seeds or buy transplants.
If you opt for the former, it is best to sow seeds directly into the container to reduce any potential risk of transplant shock. Sow two or three seeds an inch deep in the soil and keep it moist. Once the seedlings emerge, thin them to keep the strongest one.
You can buy transplants from a garden center, nursery, or online – which is what I did. Dig a large hole in the soil and carefully transplant the seedlings ASAP into the large pot to avoid them getting pot-bound or shocked.
Watermelon plants can be left to trail across the ground, or be trained up a strong trellis. Growing watermelons vertically is perfect for smaller spaces, and it is recommended to have the supports in place when you plant them.
5. Give Them Sun
To grow watermelon in pots successfully, you need to put them somewhere where they can bask in lots of sunlight over the summer.
Watermelon plants need heat and sunshine to grow and develop the sweet fruits. Place the container somewhere that gets 8 to 10 hours of sunlight each day and temperatures over 70°F.
Gardeners in cooler climates may need to grow watermelon in pots in a greenhouse or cold frame to guarantee the temperatures required for optimum growth.
This four-foot-tall portable greenhouse at Wayfair could house a compact watermelon plant (it has removable shelves) and provide a warm, protected place to grow.
6. Water Regularly and Consistently
The name gives it away – watermelons need a lot of watering throughout the season. This is especially true when you grow watermelons in pots, as the soil can dry out really quickly. And you never want to let the soil dry out completely.
The key is to keep the soil consistently moist, which can mean watering once or twice a day during the season. Check the moisture a few inches under the soil surface every day – and water if it feels dry. When you do water plants, water deeply, until it starts to flow out of the drainage holes.
As the season progresses, reduce the watering when the fruits are nearly ripe.
If you aren’t confident and worry about overwatering plants, a soil moisture meter is an essential tool. You can place it into the soil to get instant information about when to water plants in hot weather.
Get a soil moisture meter at Amazon.
7. Fertilize Every 2 Weeks
Watermelons are hungry plants and need lots of nutrients throughout the season to develop their vines and ripen fruit. If you grow watermelon in pots, committing to a regular fertilizing schedule is crucial to have any chance of a good harvest.
If you added compost at planting, there will be nutrients to get plants off to a good start. In the absence of compost, add some balanced, slow-release fertilizer at planting, such as this all-purpose plant food at Burpee.
Once the plant starts flowering, start feeding it with a product higher in phosphorus and potassium, which encourages the development of fruits and flowers. An ideal fertilizer is a tomato feed, such as this tomato booster at Amazon.
Alternatively, you can use seaweed fertilizer or make your own comfrey fertilizer. Apply this fertilizer every two weeks during the summer.
8. Harvest the Watermelons
Watermelons take 70-90 days from planting to harvesting. You may need to hand-pollinate plants if they are growing indoors to guarantee fruit.
The signs to look for to know a watermelon is ready to be picked are that the curly tendril near the fruit turns brown, the rind is hard and matte rather than shiny, and the watermelon gives a deep, hollow sound when tapped.
If a fruit ticks all these boxes, cut the melon from the vine with a sharp knife, like this Fiskars harvesting knife on Amazon.
What to Shop
'Sugar Baby' is a compact watermelon variety for smaller spaces. It produces small, sweet fruits that weigh around 8 to 10 pounds.
Seaweed fertilizer can be given to watermelon plants once they start flowering. This organic feed is a blend of tropical red and brown seaweed varieties.
A drip irrigation set-up can efficiently water plants in containers without soaking the foliage, which can promote fungal diseases. This complete kit contains a mix of emitters and tubing.
Other sprawling vegetables you can grow in pots include pumpkins and squash. As with watermelons, growing squash in containers means using compact varieties, a large pot, and remembering to water and feed regularly.
The good news is that it is not as tricky as watermelons, and you can get good harvests of squash in smaller, urban gardens or on a deck or patio.
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