Tree Dahlia - probably its last days of flowering.

I love my Tree Dahlia. It is the most optimistic plant I know of. (I am embarrassed to see that I have used that line over many years). Oh well.

Tree Dahlia flowering up and over other shrubs.
It needs some protection from winds,
otherwise, it gets flattened.
Several stems on left and right have fallen over
but the flowers will still open.

Every winter, it gets cut back to the ground (or under it, technically). Then in mid-spring it starts all over again, growing fast (imagine Jack's Beanstalk plant). Then in April, it starts to open its first flowers. Today it was in something approaching full flower. In old money, these flowers are over 10 feet off the ground.

Tree Dahlia stems holding many flowers
as seen from my Back Deck.

But late this afternoon, it started to rain. If the rain comes on heavily, the flowers will bow to the ground under the weight of the water it has to carry on its 3 metre plus stems.
Normally its enemy is frost. But we have not had any here, yet, because the long dry autumn mild spell. I will know more tomorrow, or the day after.

Tree Dahlia flower

That is a shot of a single flower (as best I could manage, by holding one stem over). The flowers are simple (open) whereas most Dahlia flowers are "double". But as far as I know Tree Dahlias are always delicate flowers, like this. Some are white. A heavy flower, such as the "Exhibition" Dahlias, which the Dahlia people rave about, would surely be too heavy for the stems to carry more than three metres above ground, and catching the wind.

I have a fairly dull Japanese Maple
But today it was looking charming
in the grey light of this afternoon.

Big Frost last night

Robertson does not have an automatic weather recording station (official one, anyway). So the closest is Moss Vale.
I know I was trying to do some important writing last night, but I could not keep going, as I was so cold.
Anyway, this morning I checked the Moss Vale Weather site, and it said -5.8* Celsius. That is about 25 Km west,a nd admiotedly is more likely to be colder than Robbo. But because our climate is so moist, we get really dense white frosts, once the temperature drops low enough.
I have a sloping site, below a line of tall hedging trees, so, in winter it is in total shade all day.
Late in the afternoon (4:40PM) there was still an unmelted frost on a sand pile. There was still a "permafrost" (little crystals of ice underneath the soil, lifting up small pebbles and rocks).
I forgot to look at the Tree Dahlia, but I am sure it will have been knocked back to the ground (as it has been in previous years). I shall check tomorrow.

Tree Dahlia makes it to flowering stage.

I love my Tree Dahlia plant. To me it symbolises the eternal struggle to succeed. In truth it might not be suitable for this climate, as it barely manages to flower, before the frosts cut it down.

Bare stems (canes) of the plant
and several arching branches carrying flowers.
In my experience, this plant needs other bushes near it
to support the heavy flowering heads.

My Blogging colleague, Martin, shares my interest in these flowers, and told me (in comments on his blog) that when he lived in Canberra, he grew them there, and they would last until the first moderate frost would arrive. It seems that where he now lives, he can no longer grow Tree Dahlias. My commiserations.

This year, my Tree Dahlia has flowered better than in previous years, as Robertson has had a long, dry and warm autumn season. In fact it started life badly as the first tall stem was knocked over by strong winds in late spring, and the plant had to start all over again.

But it has made it.

The pendant flowers always look like "Pixie's Caps" to me

(Well, as Pixie's Caps are traditionally illustrated).A close-up of the "eye" of the Tree Dahlia Flower.
Click to enlarge it, to see the details.
Just lovely, in my opinion.

Winter is about to descend on Robertson.

The frost are about to descend upon Robertson, I predict.

How do I know?
Simple - my Tree Dahlia has started to flower.Regular readers may recall two similar posts, from two years ago (OK only dedicated readers will remember these posts). I link to them, for more recently joined-up readers.
The first was entitled "The optimistic nature of Tree Dahlias", published on 7 June 2006.
The second was "The Nature of Frost (and an update on Tree Dahlias)" published on 13 June 2006.

The message is clear. Tree Dahlias take so long to grow to their full height, before they flower, that, inevitably, frosts are just around the corner. This year's flowers are about 2.5 metres above the ground. The plant grows this tall every year, before it flowers. Then the frost kills all the soft tissue material of the plant, leaving only the root stock. As with normal Dahlias, the plant has a set of tubers in the ground which are the perennial part of the plant. The difference for the Tree Dahlias is just how far they have to grow before the plant is mature enough to carry flowers.

In truth we have already had a very light touch of frost - but only once, and only very, very light. I do not know the temperature, but it was not enough to count as a real frost. Just a few signs of ice crystals glinting on the roof of the car.

But real frosts cannot be far away. Get your "Winter Woollies" out of the cupboard (if you have not done so already).
Tree Dahlia growing in front of native Sassafras and Pittosporum trees. The Sassafras (taller tree on right) is about 15 metres high. The low shrubs to the left of the Tree Dahlia are all well over head height.

Cultivation note: Tree Dahlias are easily cultivated by taking a stick of the stem with two growth points (nodes). (A stick about 15 inches long, usually). This will resemble a piece of fresh sugar cane, if you have ever seen that. Lie the stem down on a shallow angle, (bottom end first) so its head is just above the potting mix, in a Styrofoam box filled to the top with potting mix. Water it, and leave it alone for about 3 months in a protected position, and when you look at it (next spring), it will have formed roots on the bottom, and new shoots at the top. Plant it out and wait for a year. My plant came as "cuttings" from a friend in Canberra. I did exactly what I have described above, and my new plant has flowered every year since. Even though it is a silly plant to grow in a cold climate, I love it for its dogged determination to prove it can survive and flower each year.

The Optimistic Nature of Tree Dahlias

Tree Dahlias are the most optimistic of plants. They grow all season in order to produce their large pink "pixie-cap" flowers, just in time to be cut down by the first frosts of winter.

This is a remarkably futile exercise, in our climate. Perhaps where they live naturally, in Mexico, the seasons are longer, the frosts less damaging to plants.

But still I like them. They are well-named, for my young plant, only in its second year, has twice produced tall growths, well over 3 metres high, then thrown some sprays of flowers. And when walking down my street the other day, I saw some towering over a neighbours shed, probably arching some 5 metres into the air. And yet, like any normal Dahlia, they are a true perennial, the annual growth dying off, leaving only the tubers, from which new growth emerges in Spring.

Of course, in the case of the Tree Dahlia, the tubers are massive. The clump from which my plants came was a division, with long tubers 45 Cm or so in length, and a total root mass which was more than the previous owner could lift, without first dividing it with an axe.

It is interesting to think that this tall plant could, overnight, be reduced to a soft brown slimy mass of pulp, after our first serious frost. And yet, from that mess, will emerge next year, even more spires of these tall flowers, in an endless cycle of trying to outlast the season, to make enough growth to flower, before the inevitable result of being cut back to nothingness. As I said at the beginning,Tree Dahlias are the most optimistic of plants.