Tree Dahlia

The odds were stacked against this plant ever surviving as it is outside its ideal climate zone, let alone flowering in its first year.

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Dahlia imperialis flower from below

First, a little recap…..

After stumbling upon a Tree Dahlia (Dahlia imperialis) in an old garden in early June last year, I went back after the frosts (which were actually very late that year) that wither these plants and asked for a couple of stem cuttings.

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Dahlia Imperialis – the parent plant. June 2014

They were put straight into the ground, but only one took – the lowest temperature we had last winter was -7°C (19°F) and we had 36 days where the temperature was below 0°C (32°F), which was very mild as we normally should have about 60+ days below freezing.

The cutting that survived emerged on the 7th of October:

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7th October

Just eight days later on the 15th of October, we had 20cm / 8″ of snow.

Happily, I choose a sheltered spot between a corner fence paling and a large gum tree, so it didn’t die. It put on reasonable growth soon after, but then was attacked by slugs with the central leader completely chewed off.

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Dahlia recovering from slug damage in December

The slug damage was above a node, and it bounced back with a tiny bit of growth by December. I held little hope of it flowering this season. It kept growing – albeit slowly. Here it is at the beginning of February still under 30cm/1′ tall.

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Some growth in February

Fast forward to April, it’s now 1m / 3′ tall and has tiny buds!

But on April 8, we have an early – though light – snowfall and freezing (32F) temperatures. That should have killed it but the shelter of the tree and fence have obviously worked their magic again:

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The first buds in April

Another cold-snap on April 20 starts off a week of foul and windy weather with severe gales and sleet, but in its protected spot, it grows some more:

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Buds developing, it is now about 1.4m/4’6″ tall

On April 25, we have a hail storm with 1-2cm hail that last for about 5 minutes.

I stood over it with a blanket to avoid the buds and leaves being shredded…(surely that is either medal-deserving or worthy of being committed!)

By May 8, it stands a little taller – probably 1.6m/5’4″ – but now the mornings are cold and although just above freezing, we are getting light grass frosts. This hasn’t deterred the plant, sheltered under the light canopy of a towering Eucalypt, as its buds begin to colour:

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Now 1.8m tall and buds are beginning to colour

May 14th, the first flower begins to open:

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Flowering time

Now the second has opened and I thought I would post a picture in case the frosts start to become too severe (The parent of this plant – which is in a more open spot –  has already been turned black by the frosts)

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Pretty, isn’t it?

It shouldn’t have flowered. But it has!

In years to come, it will get taller as it establishes – eventually it should have about 3-6 canes and each of those should reach about 3m (12′) before each frost cuts them back.

If you are thinking of growing these, below are the conditions I experienced so far this autumn.

So as long as the plant is sheltered, it should make it before the hardest frosts hit in late Autumn. If your autumn looks like this (or preferably warmer without all of the snow and sleet), then it might be worth a try – I have seen them grown in the Pacific NW and the UK (in fact the first one I ever saw was in a garden outside of Oxford):

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Daily weather conditions this autumn. March was warmer than normal, April cooler than normal….

Happy gardening 🙂

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78 thoughts on “Tree Dahlia

  1. This story of the-tree-dahlia-that-could has made me smile! What beautiful blooms from a plant I’ve never encountered. I’m also grinning at the idea of you with your blanket protecting it during a hail storm. 🙂

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  2. Kismet! It was meant to be. I loved this plant when I first saw a picture of it on-line but the NorCal mail order nursery that sells it warned that it didn’t do well in wind, of which I have plenty on a daily basis, so I passed on it. Your tale leads me to wonder if I should give it a try.

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    • Thanks Kris! They are definitely worth a try, in LA you might have to cut it back as there are no frosts, but the only other thing I would say to get this plant going is that it needs a fair bit of summer/early autumn water in the lead-up to flowering…

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    • Thanks Julie – the thermometer has a little recording system for min and max which I can save as a .txt file to be imported into programs like excel (which make it look a lot prettier than a series of numbers and commas). I don’t know if it is up to the World Meteorological standards, but it seems reasonably close to the local weather station 🙂

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  3. How lucky you are! I’ve grown this for many years and only in one rather mild fall/winter did I get buds but the frost beat the flowers. I finally got tired of cleaning up all of the stalks in the spring and let other plants take over the spot.

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    • Thanks Peter – it should have had the flowers knocked off it with the first frost – I guess the trick is to have it in a due south-facing position under a tall tree!

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  4. That’s awesome that it flowered for you! I’m jealous… every year I get so close that I can see the petals peeking out from the buds, but the very next day I always get a killing frost! Congratulations! I hope the slugs don’t get it next year.

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    • Thanks Justin! I thought it would have been finished off after the -2C/28F frost, but it survived unscathed – but any grown in the open all turned black the next day. They are forecasting showers this week, which means that the frosts should stay away and I may just get to see the whole plant in bloom!

      Liked by 1 person

    • Thanks sweetk8 – this one might be a fluke as we should normally have had a few frosts by now…I’ll have to see how it holds up later this month, but they re-shoot each spring once they are cut down.

      Liked by 1 person

  5. Your dedication has been rewarded, Matt; I don’t think I would have been outside in a hailstorm to protect a plant, that said a friend of mine, here, grew one and when it flowered we were all immediately summoned to see it before a frost which had been forecast could destroy it.

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  6. Wonderful! I love your story of the tree Dahlia (especially after I heard about your hail protection antics!) and well done you for finding just the right spot that it loves. I hope it keeps going for a while longer so those other buds open and look forward to seeing more photos.

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  7. That is great, no commitment necessary. Tree Dahlia is a new plant to me – a friend from California was here over the weekend and said he wanted one- I thought it was one of those Dinnerplate things! Thanks for the pictures, I would not have guessed that was a Dahlia at all.

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    • I reckon it will grow very easily for you – our climates are very similar (actually I think the autumn I have had is closer to a Scottish one), but they are certainly worth the effort if you have some shelter to avoid frost settling on the plant

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  8. That is one impressive dahlia!! Let’s see… I am in USDA zone 7… stats say this is a zone 8-10 plant… but with a VERY large container and bringing it into a frost free garage over the winter… hmmm…. (container would have to be on one of those wheeled dolly things…. Hmmmm again…)

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    • I think that would actually work. You leave it out until the first frost (the canes are hollow), cut those back and then wheel it into the garage – it will take quite low temperatures (just above 0F) once dormant…it’s certainly tempting!

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      • You could probably start it out in a 5 gallon/12″ plastic pot and it will be OK for a few years (that way you can also cheaply see if it will be happy with being over-wintered), but after that, probably something along the lines of a large Versailles-style planter would be what you want to house it in…like all dahlias they like good nutrients and ample water in the growing season 🙂

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  9. They grow all over the place here and frost is de rigeur. The only thing that can truly kill a tree dahlia is being munched to the ground repeatedly by determined wallabies. Mine is dead.

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    • Thanks! It is a great plant – it is tougher than most give it credit for, but the timing of the first hard frost in Nov is key to flowering (the later the better) that and protection from the wind….(!)

      Liked by 1 person

  10. Danger! New plant discovered for warm-climate areas… Sounds like it might take a bit too much water, or I’d be toying with adding it to my Annie’s Annuals list 😉 It’s incredible what you and the plant have managed to forge through to reach such a spectacular flowering point – congrats!

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  11. Thanks for this tree dahlia report, Matt, it’s much appreciated! Out of three cuttings two seem to have rooted so all going well I should see growth emerge end of the summer, fingers crossed. So excited, hope the fairies will soon wave their pink handkerchiefs in my garden. 🙂

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    • Thanks! We usually get about a dozen snow falls from late autumn to mid-spring, but we can also get snow in mid-summer! Mostly however, we get black-ice events which are really dangerous for driving

      Liked by 1 person

  12. Congrats! I think your original post on the tree dahlia was what brought me to your blog in the first place, so this is almost an anniversary for me as well lol
    It looks great and I think it’s a very cool plant to grow (if you can, which is not the case here unfortunately).

    Liked by 1 person

    • Thanks! It’s such an unusual plant and super easy to grow, it’s just that it flowers right at the time the weather starts to turn cold, so it’s always a gamble wondering whether the frosts will destroy the plant at its peak!

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  13. Isn’t it the best when all of your nurturing pays off? It’s a beautiful plant & I bet will always be a favorite of yours. I am surely learning some things from you real gardeners: It had never occurred to me to record weather conditions. No wonder it’s all a mystery to me still!

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