Dahlias are some of the most recognizable and impressive flowers on the planet. In most parts of North America, they are grown as perennials.
They’re going to be hardy flowers when you’re living in USDA zones 8 through 10, though. It’s even possible to get them to survive the winter when you’re living in USDA zone 7 so long as you’re using mulch properly.
You might be in love with the look of dahlias, and this might make you want to grow some in your gardens soon. If you’ve never grown them before, then you likely don’t even know how big they get.
How big do dahlias grow? Can you make them grow bigger if you do certain things?
Read on to learn more about what to expect.
Understanding How Big Dahlias Can Grow
Understanding how big dahlias can grow will be relatively simple, but you need to know that there are many varieties of these plants out there. There are too many types of dahlias to go over each and every one of them, but luckily all of them can be whittled down into three convenient categories.
There are small dahlias, medium dahlias, and large dahlias. This is pretty easy to remember, and you can expect different growth ranges in each category.
Small dahlias will only grow to be between 10 and 20 inches in length. These adorable and eye-catching flowers will be a great fit for planters and garden borders.
Medium dahlias are going to grow to be a bit larger than the small ones. They will grow to be between one and two feet tall.
Large dahlias are the biggest of the bunch and they can get as tall as four feet. They’ll grow to be between 10 and 12 inches in diameter as well.
How to Grow the Biggest Dahlias Possible
Now that you know the basic expectations for how big dahlias will grow, it’s time to discuss how you can make them grow as big as possible. Of course, if you want to enjoy really large dahlias, then you’ll need to pick a variation that falls under the large category.
That being said, there will also be some other things that you can do to help encourage good growth. It’s all about how you care for these plants and whether you’re willing to put in the effort.
Remember to Care for the Tubers
Some gardeners don’t take the time to care for the tubers and it winds up negatively impacting the dahlias. To get the best dahlias that you can, it’s going to be necessary to care for the tubers before you even start noticing sprouts.
Before planting the dahlias, you must be certain that the soil is warm enough for them. If you plant them in cold soil, then they’re simply going to rot away and die.
Check the temperature of the soil and ensure that it is 55 degrees Fahrenheit or higher. That will tell you that you won’t need to worry about frost in the near future and that it’s safe to plant the dahlias.
Some people even choose to start the tubers indoors so that they can get an early start. If you live in an area where you won’t be able to plant dahlia tubers in the ground until very late May or June, then this might be a wise idea.
You can start the tubers out in pots and then transfer them to the ground when the time is right. Just do your best to care for the tubers and you’ll see better results.
Ensure That the Dahlias Get Enough Sun
Of course, it’s imperative to ensure that the dahlias get enough sun. If you want the blooms to be big and beautiful, then they’re going to need enough sun to make that happen.
Pick a spot to plant the dahlia tubers that will allow them to get at least six hours of direct sunlight each day. If you can find a spot that offers eight hours of direct sunlight each day, then that is going to be even better.
It’s also a good idea to plant them in south-facing locations. This gives you the best statistical chance of seeing large blooms.
Take the time to pick a good spot for the dahlias and don’t rush things. It’s better to find a good spot for them than to pick any spot that happens to be open and get less than stellar results.
Water the Dahlias Often
Watering the dahlias often will be a necessity if you want to see them grow strong. You shouldn’t allow the tubers to dry out and this means that you need to check on them often.
You shouldn’t fully soak the soil, though. Try to keep the water near the base of the dahlia tubers and ensure that you keep the soil evenly moist to get the best results.
If you’re caring for dahlias in containers, then you’ll need to water them more often. The dahlias in containers will often need to be watered daily.
During the peak of the growing season when the dahlias have sprouted, you’ll be watering them twice per week on average. However, you need to pay attention to the plants to see when you need to water them rather than relying on a schedule.
You might have to water them more or less often depending on the temperature, whether it has been raining or not, and even the type of soil that you’re using. Use your fingers to check the soil to see if things are dry so that you’ll know if you need to water them.
Fertilizer is going to help the growth potential of the dahlias, too. When they are above the ground and they’re about six inches tall, it’ll be time to start fertilizing regularly.
It’s generally recommended to start out with a 10-10-10 fertilizer to get good results. You could also go with a 15-15-15 granular fertilizer if you would prefer.
Both are good fertilizers that will start your dahlias out right. Eventually, you’ll start to see buds develop, and this will be the time to switch to a fertilizer with high phosphorus content and lower nitrogen content.
Consider going with something like a 3-14-2 fertilizer when you’re looking to see large blooms. It should give them exactly what they need to grow strong.
Pruning can help you to get larger blooms if that’s what you’re going for. One of the best things that you can do when the dahlias are really starting to grow will be to prune off the side buds.
This ensures that the central bud is going to get all of the energy. It’ll theoretically make the central bloom that much larger.
Those who don’t care as much about flower size shouldn’t do this. If you want them to have as many blooms as possible, then you can pinch the center bud to try to get it to branch out and become bushier.
Which route you’ll want to take will depend on what you’re looking to have happen. Decide which route is best for you and enjoy the dahlias to the fullest.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.