How Do You Grow Tree Dahlias?

Yesterday, I received a tree dahlia as a gift. Despite my limited knowledge on how to care for it, I saw it as a chance to educate myself. If you are curious about these impressive dahlia plants, join me as I start my journey of discovery.

What Are Tree Dahlias?

Unlike the shorter, bushy dahlias most gardeners are familiar with, tree dahlias are towering perennials that can shoot up to 4-6 meters (13-20 feet) in a single growing season. They put all their energy in growth and it is not until late in the season, usually from late autumn to early winter, that they bloom. So just as everything else is starting to wind down, these beauties step in to brighten things up.

Originating from the mountains of Mexico and Central America, they thrive on warmth and sunlight.

Where Do I Plant a Tree Dahlia

Considering what I have just learned, in order to grow tall, throughout a long season they need warmth and sunshine. Additionally, with their rapid growth, they will need wind protection and some support, as strong winds can snap the tall stems in strong winds.

I have a garden that has a fence surrounded on three sides providing excellent wind protection and is north facing and full sun. One side of the garden is the house with a brick wall, that will provide some radiant heat and frost protection in the later months.

How Do I Plant a Tree Dahlia?

Tree dahlias grow from tubers, like other Dahlias. But they also grow quickly from cuttings or stems. My Dahlia is a tuber and well on it's way, however I will take some cuttings a plant them up to see how quickly I can get a second plant. This is the joy of curiosity and the willingness to experiment, I may just une up with many tree dahlia's.

Then I wait...

Here’s the thing about tree dahlias; You won’t get instant gratification. They shoot up fast, but they only flower when most plants are winding down for winter. I’ll have to wait months before I see any blooms—and even then, there’s no guarantee. A late frost or unexpected cold snap could ruin the whole show before it even begins. I’m hoping that our mild winters here in Australia will work in my favour...only time will tell

Maintenance

Apparently, pruning is crucial to keep these giants under control. After flowering, the tall canes die back, and you need to cut them down to ground level. This encourages new growth for the next season. I’ve also read that many gardeners like to cut sections of the stem and use them as cuttings to start new plants—a bit like sharing the joy around. Maybe this time next year, I’ll be the one gifting someone else a tree dahlia!

Honestly, I’m both excited and nervous about growing this plant. I’ve never grown anything that can potentially hit the roof of the house in just a few months. There’s a lot to learn and a good chance I’ll make some mistakes along the way—especially with things like wind damage or pruning. But that’s all part of the fun, right?

For now, I’ll be patient, keep watering it (but not too much), and see what happens. If it blooms, I’ll be thrilled. And if it doesn’t—well, at least I’ll know what *not* to do next year.

Final Thoughts

Tree dahlias feel like one of those plants that reward experimentation and persistence. If you’re someone who loves the idea of growing something unique and dramatic (and you have the space!), they’re definitely worth a shot. I’ll keep you updated on how mine goes—if I manage to avoid snapping it in half before winter, that is.

Here’s hoping for some spectacular flowers come late autumn! Stay tuned.