For some basic information on tree dalhias, check out this facts sheet from Burke's Backyard.

Here is a link that might be useful: http://www.burkesbackyard.com.au/facts/1999/garden/treedahlia_17.html

From what I have seen, they put up a few stalks, to a height of about 2 to 3 metres. They are rather spectacular in bloom. They don't take up a lot of garden space. I would allow about 1/2 metre square. Most of the plant is above the rest of the garden.
They are reasonable frost tender. When they start to die back, you can cut up the stalks and store them for next year, or share them with friends.
Cheers, Jan

Do I gather from that, Jan, that, after flowering, the whole plant will die back and then, next year, will re-shoot? or do I need to take cuttings for the next year?
Annie

Hi, Annie, I can give you some information as it applies to Melbourne. Tree dahlias have bamboo like stalks that rise up to four to five metres. They flower in early June and have large pink blooms right on top of the plant so it looks spectacular. You can propogate them by dividing the "bamboo" sections and each piece will grow. After blooming, they die down until spring.

Anopheles

When propagating its best to lay the pieces on their side.

Yes Alison, lay them on their side, and the new shoots will come up from the node. My friend puts them in a bucket of water to get them going. A bit of sea weed extract would help too.
Cheers, Jan

The record for the worlds biggest tree Dahlia is in a garden in Western Australia, 27½ feet. Mine grew to about 24ft the first year.

oh! my! god! 24ft in the first year! I take heart from the fact that I'm not as good a gardener as you are, Sheila. LOL
Annie

I gave up after they reached their peak of flowering only to fold over and snap off in the wind. I think they must need full sun to do well, which mine didn't have.

Annie - 24 ft in the first year, but no more in the second. They die back and you start again every year, as they are perennials, like ordinary dahlias.

I'm sorry to seem so dense but, when you say "they die back and you start again every year" does that mean that I have to replant or the plant will re-shoot?
Annie

They will re shoot, but you can also cut up the old stalks into sections with 2 nodes, and lay them on their side covered with a little soil. New shoots will grow from the nodes.

At 24 foot, if you broke them all up and grew them, good heavens, you'd end up with a forest of dahlias in no time at all!
If they are that easy, why do you not see more of them?
I'm looking forward to seeing mine with flowers. Of the 4(?) pieces I got, I think 3 have definitely taken but the fourth has yet died so I have hopes for it.
Annie

I have grown the pink variety of tree dahlia for 7 or so years.They have huge tubers under the ground and these are what reshoot every year. They are a dahlia after all. No need to dig these up and when you do try you will find that the tubers reach 1 metre from trunk. I find they grow easy and that they can over shade other plants for a few months of the year till they finish flowering and die back. Good Luck

MY TREE DAHLIA GREW QUITE TALL, AND AT THE FIRST BIG WIND BLEW OVER. I WAS VERY HAPPY TO SEE A STUNNING VIOLET BLOOM ON IT, SO I CUT IT INBETWEEN NODES AND HAVE IT STANDING IN A BUD VASE.

IS IT PROPER TO ASK FOR CUTTINGS? I WOULD LOVE TO GET A CUTTING OR TWO OF THE SINGLE AND DOUBLE WHITE "ALBA".

It's fine to ask for cuttings but you will need to go to the US forums plant exchange for that. This forum is Australian.
Cheers, Jan

Oh my goodness! If the tubers grow 1 metre from the trunk, that makes the tuber 2 metres in diameter ........ egads! Alison, get your Mum out there with that crowbar! :)

Pam

I do so enjoy reading all these comments and having a good laugh...such as Pam's last remark. It made sense after reading about Alison's Mum's accident on another forum. I too have had success with tree dahlias but the thought that under my entire garden is one huge tree dahlia bulb scares the hell out of me...do they come out at night?? ... and what will it be like after a few more seasons when I have only just planted the double and the mauve???? HELP!!

Your whole house block will be undermined by one enormous clump of tree dahlia rhizomes Jen. That shouldn't cause problems as they are fairly solid things, unless they are over watered .... and start to rot .... and the centre of the rhizome caves in ... and the house foundations start to shift....

Thanks Jan!!!...I have enough trouble sleeping at night without the threat of an attack from the dreaded tree dahlia rhizomes!!! But I love the flower enough to RISK IT!! Live dangerously I say!!

I DO love reading these forums. I love a good laugh. I have visions of poor Jen sleeping innocently one night when, in thru the window, creeps the dreaded dahlia rhizome!
Can she escape? or will morning find her trapped,helpless, in its coils? (do rhizomes have coils?)
Annie

Help!!!!

I have been planting tree dahlias to sell at our school fair for years. I plant two 50cm cuttings upright in to a large pot they always sell like mad and grow like crazy.

Hi Annie
I'm also a Queenslander and the tree dahlias are very easy to grow and hardy. Ours hardly get watered as we are on tank water. Just lay sections of cane horizontally about 6" beneath the soil and they will shoot from each growth band around the canes. The same clump will shoot again next season or plant extra ones from the stems once they have died off. We have single mauve, single white and double white. Watch them in windy weather as the stems are hollow and will break with the weight of the flowerheads. Have fun with them and they are great for raising money at fetes, etc.

I grew Tree Dahlias for the first time last year, and they are in full flower at the moment. They are virtually unkillable (my husband accidently mowed them down when they were small) and stunning in flower. I just laid the pieces of stem horizontally in the ground last winter, and ignored them!! I planted mine fairly close to a fence though, as they are very tall and need some support and protection from strong winds.

I have a tree dahlia that been in the ground 3 years, and it reached the guttering on the house, which is about 25ft! The main trunk is over 2 inches in radius!

I made a mistake with where I put my piece of dahlia so I'm now going to shift it. It really didn't do too well - not enough sun but it did flower.
Annie

What causes the buds to fail to open? I had many buds but only about 1/2 opened and the rest rotted. Is it frost or lack of sun, as there is some shading by a silver birch?

I really don't know but, if the rest rotted, could it be over-watered?
Annie

Probably frost.

I've really enjoyed reading about the tree dahlias. I have been growing them in a clump for about 10 years, & just cut them down at the end of every winter, & they resprout. This year, for the very first time, they were heavily pruned by possums, walking along the roof of the house, munching. As a result, there were only one or two flowers.
Possums have ignored them up until now,but Melbourne is having a possum plague. They may have been safer had they not been planted alongside the house. The tubers haven't lifted my house out of the ground yet, & everything else around them is thriving.

What a great read about Tree Dahlias.

I watched last year Monarch Butterflies feeding on tree dahlia flowers, it was great because at this time of year nectar food becomes scarce.

A fellow gardener took cuttings for the butterfly house and they preceeding to grow to at least 7 feet, desparately need staking, they break easily. Unfortunately by the time they flowered in the Butterfly House we were out of butterflies for the season.

The tuber is huge. Would love other colours, if any!

Raine

Can I send tubers to N.Z.? if so,what colour do you have,I have single white and single pink still not cut,the double white is already cut and -planted. let me know and we can arrange something for postage Judie

Just thinking......... seeing as they are indeed a dahlia, is there any reason you couldn't keep pinching the growth to encourage the plant to bush to a manageable size rather than growing straight upward?

Pam

I have been reading about tree dahlias in this forum and they sound spectacular. Would anyone be able to tell me where I can find some in Sydney? Better yet, would anyone be willing to trade?

Saunthi

Not a good time to trade, as they are actively growing. If you keep my mail address, and contact me in Winter, I will see what I can do about sending you some.
Cheers, Jan

Thanks again Jan.

Saunthi

Hi all,

Anyone know where I can find a double pink tree dahlia? I've heard that they exist but can't find them in the nurseries.
I live in the northern suburbs of Sydney so somewhere close would be nice.

The Diggers Club is selling the double pink. Hope this helps, from Mandy

Thank you, Mandy. I'll check them out.

So Annie, what colour/s did you end up having?

Incidentally, with regard to my earlier post,

"is there any reason you couldn't keep pinching the growth to encourage the plant to bush to a manageable size rather than growing straight upward? "

the answer is, there is no reason whatsoever - it works very well. Mine are a very respectable 7 feet (couple of metres), and nice and bushy, with the blooms at eye-height.

Pam

I think I will be an ex-tree dahlia grower, they flowered just in time for gales and heavy rain, same happened last year :(

I must admit, this has been one of the funniest forums I have read lately. I have been meaning to try these myself and would appreciate any cuttings. My closest contact has been with my neighbour who must have thought she was planting ordinary dahlias. She put them right in the front of her border and they are over nine feet high and doing very well. Full sun and completely unsupported. Even the last big blow didn't knock them over, which surprised me. She is a new arrival from Mauritius and probably thinks she has the greenest thumb in the neighbourhood. Nobody has had the heart to tell her they are tree dahlias. :)

Lay the tube you were given flat under the ground and water regularly. They grow about 2 to 3 metres high. Mid winter they need to be cut to the ground to start over or as my neighbour did he grew it for a few years as it took longer to get going. My flowers are high double white ones. Some are purple. Good luck.

Hi everyone, do the tree dahlia flowers last in a vase? for how long?

Many tuberous dahlia can be prepared and consumed like potatoes or cooked carrots; Additionally, the petals can be eaten on green salads or soups, and tree dahlia leaves are used as a dietary supplement.

https://www.inaturalist.org/taxa/288936-Dahlia-imperialis