If you don’t have a large garden space, you might not have considered growing watermelons before. Watermelons grow on vining plants and can take up lots of space as they trail along the ground. But, I’m going to explain how to grow watermelon on a trellis vertically.
By utilising vertical gardening and a nice sturdy trellis, you can grow lovely juicy watermelons even if you have limited space. All you need is a raised garden bed or large container and a suitable trellis to keep the vines off the ground.
Consider choosing the varieties of watermelon that you want to grow wisely. This is because plant breeders have developed plants that bear smaller fruits. These are ideal for growing vertically.
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So, let’s first look at some watermelon cultivars that are ideal for growing on a trellis.
Here are some of the most compact watermelon varieties that bear juicy but small fruit.
Sugar Baby Watermelon
The fruits on this compact cultivar have impressive dark green skin or rind and lovely red flesh. Each fruit weighs around 8 to 10 pounds (3.5 to 4.5 kg). Their size is around the same as a small ball, making them perfect for growing on a trellis.
This is another compact variety that has very dark green or almost black skin. The flesh is a lovely crimson colour. It actually grows quite fast and the vine can be highly productive.
Small Shining Light
This heirloom variety also has very deep green skin and bright red flesh. It will produce fruits that are around 12 inches (30 cm) in size.
This sweet little variety will produce seedless watermelons that have striped skins. Each fruit only weighs around 4 pounds (1.8 kg).
Another compact cultivar, this variety will produce oval fruits that are about the size of an adult hand. The skin is very dark green and the juicy flesh is bright red. This is also a lovely sweet variety.
This is another striped variety that produces melons that weigh around 3 to 6 pounds (1.4 to 2.7 kg). The flesh is bright red and has just a few small seeds.
This compact variety has the traditional striped green skin but the flesh is a golden yellow colour. It grows in a similar fashion to sugar baby.
Another small variety, golden midget produces fruits that are around 3 pounds (1.4 kg). The skin is golden yellow in colour and the flesh is salmony-pink.
With all these smaller varieties to choose from, you’re sure to find one or two that you really want to grow.
Now, let’s look at the ideal way to grow these small watermelon varieties on a trellis.
Choose Your Ideal Spot
To achieve maximum success, it’s a good idea to give your watermelon plant at least 8 hours of sunlight daily. Plus, watermelons need fairly deep soil as they have a large root system.
So, if you have some outdoor growing space, you might want to think about installing a raised bed that is around 4 feet by 4 feet (120 x 120 cm).
However, if all you have is a balcony or small patio, you could consider growing your plant in a very large pot. Make sure that the pot is as deep as possible to accommodate the root system.
In fact, if you plan to grow your watermelon on a balcony that has a nice sturdy bannister, you might not even need a trellis. Instead, you could guide the vines to grow up, around and along the bannister.
Expert tip: If you’re growing in a raised bed on the ground, don’t line the base of your bed with a weed mat. You want to allow the roots the ability to travel deep down into the soil and even beyond the raised bed.
You also want to refrain from growing anything else in the bed once your watermelon plant starts to produce its trailing vines. This will ensure that the plant growth is not stunted and you get a decent number of fruits.
Fill Your Garden Bed Or Your Large Container With Quality Well-Drained Soil
If your garden bed is relatively deep, you can fill the base with good-quality garden soil and then layer the top with well-aged compost and premium potting mix. The soil should have a high level of organic matter and be free-draining.
On the other hand, if you’re growing in a large container, only use premium potting mix and well-aged compost. This is because garden soil doesn’t have the right structure for container growing and will become too compacted.
Creating Your Trellis
When you are creating your trellis, you have to remember that the watermelon vines can get quite long and the fruits will get heavy as they mature. For this reason, you have to build a fairly sturdy trellis to withstand all that weight.
There are a few materials that you can use to build your trellis but, the sturdier the better. One popular choice is to use livestock panels. These are made from steel and will be both tough and fairly easy to erect.
All you’ll need is some strong posts at either end plus a couple spread evenly in the middle. Make sure that you really pound these posts or stakes into the ground so that they won’t easily fall over under the weight.
You could also consider using welded wire mesh fencing which is equally as tough. If you visit your local garden centre, you should be able to find some ready-made options that will work for you.
If you’re planning on growing your melon in a container, trellising could be a little more challenging but there are solutions. You can purchase large wooden planter boxes that already have a wooden trellis attached to one side.
These will work if you provide them with a little extra support. For example, place the planter next to a house or garden wall and secure the trellis to the wall in a number of spots. Or, you could just grow your watermelon in a large container next to the wall or even a fence and attach a trellis to the fence or wall.
When planning your setup, just remember that you want to provide your vertical watermelon vine with enough support so that it has no chance of toppling over.
Should You Grow From Seed Or Watermelon Seedlings
As melon plants develop a tap root, it’s far better to grow them from watermelon seeds. This allows the tap root to go deep down into the soil and will result in a more vigorous plant.
On the other hand, if seeds are grown in punnets and you then transplant them, often the tap root has been stunted by growing in the punnet. Once this deep-growing root hits the bottom of the punnet, it has nowhere else to go.
Ultimately, this can cause the root to either stop growing or to grow sideways. Neither will allow the development of a healthy and vigorous root system.
So, what about if you’re growing in a container? Of course, once the tap root reaches the bottom of the container, the same thing will happen. This is why it’s crucial that you use a really deep container.
What will happen is that your plant should still grow and produce some fruit for you. But, it just won’t produce as much as a plant whose tap root has been allowed to grow as it wants.
You’ll also find that container-grown watermelon plants will need a lot more water than those grown in raised beds. Plus, you’ll need to supply a decent amount of fertiliser to feed your plant.
How To Train Your Plants To Grow Up The Watermelon Trellis
Although watermelons grow on long vines, these do not have the capacity to grow up the trellis on their own. This means that you have to train and guide them to grow where you want.
You also should be aware that these plants can grow really fast. In fact, you can expect each vine to grow by 1 to 2 feet (30 to 60 cm) in just one week. What this means is that you have to be vigilant and keep an eye on your plants as they grow.
It’s much easier to tie each vine to the trellis as it grows rather than trying to untangle the vines once they’ve put on a substantial amount of growth.
You can use a variety of materials to tie your vines to the trellis. Garden twine works well but make sure that you don’t tie it too tight so that you don’t damage the stem.
Alternatively, if you have some plastic bags lying around, you can cut these into strips and use them to tie up your vines. You could even use zip ties as long as you don’t tie them too tightly.
It’s generally best to make a figure 8 loop and to loop whatever you’re using just below a leaf joint.
How To Keep Your Vine Tidy
Not only will your watermelon plant produce a number of main vines from the base of the plant, but secondary vines or side shoots will often grow from the leaf axis of these main vines as well.
Once again, this means that you have to be vigilant and tie up all those vines as they start to grow. However, if your trellis is starting to get too crowded, there’s no harm in trimming off some of those secondary vines in order to give the remaining vines room to grow.
Supporting Your Growing Melons
As your vine starts to produce its heavy fruit and these fruits start to grow, you will need to support the weight of the melons. If you don’t, they’ll get too heavy for the vine and break it.
Therefore, you’ll need to make some slings that you place under the fruit and tie onto the trellis. I did this last year with a pumpkin that I was growing over a low support.
For this, I just cut off a piece of bird netting and made a little hammock for the fruit to sit in comfortably and then tied the loose ends of the netting onto the support.
Now, you can use almost anything to make your melon hammocks such as bits of fabric, those mesh bags that onions come in or even old nylon stockings or pantyhose if you have any. You can even cut up some old t-shirts to make suitable hammocks.
Just make sure that the hammocks are strong enough to support each fruit so that the weight of the maturing fruit doesn’t put any stress on the vine.
Giving Your Plants The Care That They Need
Apart from tying up the vines and creating hammocks for the fruit, you also need to ensure that your melon plants get plenty of water as they’re quite thirsty plants.
After all, they’re not called watermelons for no reason! When watering your plants, you want to give them a good soaking at least once or twice a week. Make sure that you water at the ground level so that the water can get down to the roots.
You also want to avoid getting the leaves wet as much as possible so that you don’t end up with fungal diseases such as powdery mildew. For this reason, I find soaker hoses invaluable in my vegetable garden.
For plants grown in containers, you’ll probably need to water them daily. Make sure that you water deeply and only stop when the excess water comes out of the drainage holes in the base of the pot.
You also want to make sure that you feed your melons as they’re heavy feeders. Choose a fertiliser that’s high in potassium as this encourages more fruits to grow. In garden beds, you can easily just apply a slow-release fertiliser once the vines reach the fruiting stage as this type of fertiliser can last for around 6 months.
However, for pot-grown plants, it might be better to apply a liquid fertiliser high in potassium on a weekly basis during the fruiting stage.
How To Know When Your Fruits Are Ready For Harvest
Harvesting your fruits is the fun part because now you get to enjoy the fruits of your labour. But, how do you know when the fruits are ready for harvest?
Actually, it’s quite easy. The best way is to closely examine the fruit. Next to the stem of each melon, you’ll see a small green tendril. When this tendril starts to turn brown and dries, the fruit is mature and ready for harvest.
Use a sharp pair of secateurs to cut the stem from the vine. Don’t be tempted to just pull it off because you might damage the vine in the process. Then, all that’s left to do is enjoy the sweet, juicy flesh of your ripe melons.
Frequently Asked Questions
You might be surprised to learn that there are actually 1200 varieties of watermelon. But, only about 200 to 300 of these are commonly grown these days.
Yes, both yellow and orange watermelons are usually sweeter than the ones with red flesh.
Tapping a watermelon with your finger is another way to tell if the fruit is ripe. If you hear a hollow sound when you tap the outside of the melon, then you can be assured that it’s mature and ripe for harvest.
Yes, just like pumpkins and zucchinis, watermelons have both male and female flowers on the same plant. This means that the female flowers need to be pollinated with the pollen from the male flowers to produce fruit.
Watermelons are warm-season crops and are generally grown over the summer months in most regions. The soil temperature needs to be warm before the seeds will germinate.
Watermelons are fairly thirsty plants so they need plenty of water during the growing season. Ideally, you want to water your plants at least once or twice a week and pot-grown plants daily.
You can grow watermelons even if you have limited space or only have a small garden. All you have to do is choose some of the smaller melons and grow them up a trellis. As long as you give your plants plenty of support and create supporting hammocks for the fruit, you should be able to get a decent harvest.