PlantFiles: Tree Dahlia
Dahlia imperialis

I wasn't sure what would happen to this plant in zone 10a but it's been a wonderful experience. The plant flowers weekly and often has two or three blossoms at once swaying atop ten foot stalks. I have it caged against a sheltered wall where the wind cannot harm it. It also only receives brief midmorning sun. I wasn't sure when to cut it to the ground here as it never stops flowering. Now I just cut it when it starts to lean over too much onto the supports. It is a very delicate plant and new growth will curve away from the supports or any other stalks it touches.

This plant has happy daisy-like flowers that seem to smile down at whomever is looking up at them! A friend gave me a cutting of a Tree Dahlia a year ago. I planted & supported it against an East-facing backyard fence, & it bloomed around Thanksgiving, when everything else was going to sleep. I was told to remove the new growth that forms at the "crotches" when the plant goes dormant in winter. I planted those in pots & gave them to some friends. Also, I was told to cut the plant to the ground when dormant, & it will come back. Since this is my first year with it, I was hesitant to do that, but I did cut it to the ground. My friend has assured me that it will come back . I'll let you know if it doesn't....

I have had the same experience with it snapping off. Here in zone 9, it grows to great heights, 15 to 20 feet high some seasons. But if we have a strong summer windstorm, many branches will be damaged, some broken back to the main stump, others with side branches maimed. It tends to drop lower leaves gradually up the branches as the season progresses, but it's easy to clean up after. It flowers sometimes very early in the season before the heat hits, and then the biggest bloom comes at the end of summer, when it cools down. This specimen came from CA central coast and grows rank over there. I've never had a volunteer come up from seed, which are spread everywhere. It's either too hot or too cold after bloom I guess. Very beautiful foliage, the long branches sprouting from the main trunk look somewhat like maroon bamboo with foliage, and are actually hollow inside when cut. Interesting plant to grow.

Two years ago we found a neglected tree dahlia in our new back yard. It grows very quickly but is not very strong, so new shoots would grow out about 6 feet sideways before snapping and breaking under their own weight. Since I started supporting the branches it has done very well, growing over 20 feet high. The first year, it produced around 3 flowers. This year it produced somewhere around 200. Beautiful. After the flower fades, a brown "bud" of dry petals will appear. These petals blow off in the wind, carrying one seed per petal. It is easy to pluck the whole brown bud off (except they tend to be high up out of reach), but I do not know an easy way to separate the seeds from the petals. (It is easy to separate a seed from its petal, but there are over 100 seeds per bud so I don't have the patience to do them one by one after collecting dozens of buds.) Given that it produces tens of thousands of seeds, I'm afraid individual seeds might not have a high probability of success. The tree is very sensitive to water, with leaves turning brown any time there is too little or too much water, but it grows so quickly it always has plenty of leaves anyway.

The tree Dahlia gets very tall, while not having many flowers, and they bloom late here. They are blooming here at Thanksgiving. The foliage is beautiful. I use it behind a fence and the flowers bloom just above it. My Dahlia actually grows between a fence and an olive tree, to keep it from blowing over. It seems to need very little sun to begin.