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A befuddled mind can still grow a beautiful plant! My stumbling journey toward successfully growing a Tree Dahlia (Dahlia imperialis), which was received as a free gift in a Dave's Garden plant trade by mail, and what I learned along the way.
It arrived as a tuber tossed in as a “freebie” in a box of plant swaps from my DG friend, KayJones. As was my habit at that time, I potted up the tuber and set it aside without putting a label on it. I thought, because it was so unusual, I would surely remember its name. I have since recognized that my memory is not always as acute as I would like it to be. I have a few dozen UFOs (Unidentified Flowering Objects) sitting around in pots in my yard from roundups and propagations from friends. I’ve come to appreciate the value of providing a common name, or more preferably the botanical name, on a permanent label for a plant upon receiving it. I otherwise spend hours in frustrated befuddlement trying to ascertain what plant I have. If my angst finally grows great enough, I post a photo of the plant in the DG Identification Forum. I usually have an answer within a short time.
The freebie tuber soon sprouted leaves. I decided to set it out in my garden when it reached about a foot in height. By this time, I had not only totally forgotten what the plant’s name might be, I had also forgotten whom the generous donor was. I had to guess what conditions the plant might prefer. Assuming that most plants need ample sun, I chose a spot with mostly full sun and a hint of afternoon shade. I watched the plant for a few weeks and was disappointed that its initial growth spurt now seemed stunted. In my attempts to recall some known plant that it might match, it began to look a lot like a large Bidens alba var. radiata -- my garden’s most prolific wildflower (which some might call a “weed,” but I value the Bidens for its benefit in providing year-round nectar for butterflies).
After about a month with no new growth, I decided the plant might benefit by being transplanted to a new location. Fortunately, I made the choice to provide more shade rather than more sun. Still wondering if it might be an ordinary B. alba ’Radiata,’ I stuck it in a somewhat shady corner of my butterfly and hummingbird garden, with the certainty that I could always pluck it up later.
Once it was in a shadier spot, the plant shot heavenward. When it reached about eyeball level with my six foot frame, I was certain that it was not a Bidens, but thought that it could be Jack’s beanstalk.
It capped out at about seven feet and began to make flower buds on the topmost branches. The waxy, layered sepals on the buds reminded me of a dahlia, but I couldn’t imagine any dahlia growing this tall. Our northeast Florida subtropical heat and humidity are generally considered not to be conducive to growing most dahlias, so I doubted that my guess at identification was correct.
When it flowered, I saw what I was fairly certain was a dahlia blossom! I posted some photos of the plant and blossoms in the Identification Forum. It took ecrane3 only two minutes to provide me with the correct designation for my adoptee. It was a Tree Dahlia (Dahlia imperialis) Dave's Garden Plant Files Page - Tree Dahlia , a splendiferous plant to behold!
With a name in hand for the plant, I was able to research its cultivation requirements. The plant generally prefers part shade and is reported to grow about 8 - 15 feet high, though some observers claim to have seen the plant reaching up to thirty feet in its native habitat of the high Sierra Madre mountains of Mexico (where dahlia is the National Flower). The hardiness is usually listed as being limited to Zones 7 - 8, but it is growing very well in my garden, situated precisely on the borderline of Zones 8b/9a.
After getting the plant positively identified, I started a thread in the DG Florida Forum to find out if any of my online “neighbors” were growing this plant, but no one was. I had never seen it in any garden in my region nor for sale in any local nurseries. The only comments in the Plants Files were from California, where Tree Dahlias may be fairly common.
The lack of widespread use of D. imperialis may be due to its short October - November flowering period just prior to freezing, and its limited tolerances for heat and cold. The plant can take a mild frost, but will die back to the ground with freezing temperatures. It returns from the root crown the following Spring. The tall, celery-like weedy stalks may not be attractive to some people, but the flowering phase, with clusters of four to six inch wide blossoms, and the bizarre novelty of having a dahlia plant taller than most humans is worth the space in my garden. The hollow stalks may be easily broken in winds or from the weight of the flowers, but I’ve not experienced this problem.
D. imperialis usually bears a pink/mauve flower. It has cultivars that include a white, double-white, and double-pink flower. There may also be red and yellow imperialis, but other than undocumented photos that can be viewed on this link, these remain only an elusive rumor. Another tall-growing dahlia species, D. excelsa, is somewhat smaller than D. imperialis and has an earlier bloom time. It might actually be a better choice for most climates.
I intend to slice up my D. imperialis for propagation just prior to our first freeze this upcoming winter. A segment containing at least two nodes can be placed, either vertically or horizontally, in consistently moist potting soil; or divide the tubers.
I am now on a quest to obtain all the varieties and species of the Tree Dahlia for my garden collection. This plant’s regal stature brings a crowning touch to the end of the growing season. I will make room for massive arbors of it wherever I can find a suitable space in my garden!
About Jeremy Wayne Lucas
Jeremy (JaxFlaGardener) is a frequent contributor to the Florida Forum and other forums on Dave's Garden. In an ideal world, he would spend nearly every waking moment gardening, oil painting, and writing. Lacking such a Utopia, he currently works part-time in the Horticulture Department at the Jacksonville (Florida) Zoo and Gardens. His own half-acre garden is a hodgepodge of just about everything that will grow in Zone 8b/9a, with a homemade greenhouse for his orchids. He is a Master Gardener who esteems digging in the dirt more than book learning, but greatly enjoys research about plants and botanical nomenclature. He is pictured here with one of his large paintings, "The Healer's Leaves," based on a wonderful photo by DGer GardenWife of Ricinus communis (Castor Oil Plant) used by permission.
Posted by ezgroonly (from Fountaintown, IN) on September 12, 2007 at 10:37 AM:
I wonder how it would fare in an Indiana garden. Of course, I would over-winter it as I do other dahlias, after the first frost. Are you willing to share?
...
Posted by JaxFlaGardener (from Jacksonville, FL) on September 12, 2007 at 11:52 AM:
This winter will be my first attempt to propagate the D. imperialis from stem cuttings. As noted in the article, I plan to chop up the stalk into segments with 2 nodes each and place them in potting soil. If successful, I will be more than happy to share this wonderful plant. Send me a D-mail, please, as I tend to often wander off into oblivion and forget about committments and appointments, etc.
An update on my plant: It hasn't bloomed yet this year, but I expect to see the buds soon. This year, the plant is about 8 ft tall and the stems are over an inch in diameter! It seems to grow a little larger and stronger each year that it returns.
Thanks for inquiring!
Jeremy
...
Posted by ezgroonly (from Fountaintown, IN) on September 17, 2007 at 3:35 PM:
Hi Jeremy,
Here's my first Dmail; I'll Dmail monthly until D. imperialis arrives in my mailbox. See my tradelist entries for something you'd like to have. Or, I'll gladly reimburse your shipping cost.
Many thanks!
Carol
...
Subject: Great article!
Posted by jannich (from Red Level, AL) on August 20, 2007 at 7:14 AM:
Really enjoyed the article.I have never heard of a tree dahlia before but would sure love to grow one in my garden.
...
Posted by melody (from Benton, KY) on August 20, 2007 at 8:52 AM:
Loved it! Your experiences sound like mine....I'm always forgetting to label!
...
Posted by Sashagirl (from by the Muddy Miss., IA) on August 20, 2007 at 9:55 AM:
I loved the Article.
Amusing, informative and VERY well done.
I appreciated the strain of thought that says to us-sometimes, the best thing we can do for our plants, is "just pay attention" to them. Even when we don't know what a plant is (for one reason or another), if we watch them closely, observe what makes them happy or sad-we can help them to flourish.......kinda like dealing with people and fur friends, huh?
Thanks for a great start to my day.
Sasha
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Posted by sugarweed (from Jacksonville, FL) on August 20, 2007 at 1:44 PM:
Great article Jeremy.
Please save me one of those two node pieces.
Sidney
...
Posted by JaxFlaGardener (from Jacksonville, FL) on August 20, 2007 at 1:48 PM:
You got it, Sugarweed!
Jeremy
...
Posted by bigcityal (from Menasha, WI) on August 20, 2007 at 5:27 PM:
Good job Jeremy. I grow a lot of dahlias, but have not tried a D.I. yet.
...
Subject: What a fun surprise!
Posted by KyWoods (from Melbourne, KY) on August 20, 2007 at 1:15 AM:
How exciting to have your "Unidentified Flowering Object" (love that!) turn out so magnificent! Surely, your neighbors have inquired about this one-of-a-kind plant in your area. Who knows, you may start a tree dahlia craze among the locals.
Very informative and fun article. Thanks for sharing all you've learned about your beautiful plant, and the pics, too. I love dahlias, and had no idea that one existed!
...
Posted by Dea (from Frederick, MD) on August 20, 2007 at 7:15 AM:
The blossom is spectacular as well as the height of the entire plant. I had no idea of this and thank you for an informative and very fun article.
**zone envy** !!!
Dea
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Posted by Kathleen (from Panama, NY) on August 20, 2007 at 8:58 AM:
great article - another plant that will never grace my zone 5 garden, but fun to read about.
(good job on the bio! ; )
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Posted by gardenglory (from Gainesville, FL) on August 20, 2007 at 9:59 AM:
How funny, I was just going to comment that Jeremy, from Jax., in the FL forum had talked about one of those, and how excited he was about it. Funny how adding a middle and last name, didnt connect. Great article.
On the news this (late) fall, there were people all crowded around one in central park. I guess it has been there for years and years, but never ever had it bloomed. It had blooms on top, just like your picture. The people were SO excited. I think it snowed about a week after that.
...
Posted by JaxFlaGardener (from Jacksonville, FL) on August 20, 2007 at 11:48 AM:
Thanks, all, for your kind comments and encouragement!
GardenGlory, was the Tree Dahlia in Central Park in NYC? If so, it's zone limits could definitely be extended, or maybe it was planted as an annual to grow and die in one season?
BTW - my decision to include both my first and middle name in my bio was brought about by my doing a Google search for "Jeremy Lucas" and finding there were already published authors by that name, as well as another actor that is working under MY name (but he is allowed, because I've been on "honorable withdrawal" status from the actor's unions for more than 10 years). Since this was my first time out as a published author, I decided to toss in my middle name so that there would be less confusion with all the other "Jeremy Lucas" writers, actors, engineers, and even a ficticious doctor on the current "Star Trek" TV series. If you have never done a Google search for your own name, I would recommend it, though it will most likely lead to you feeling not so unique anymore. LOL
Jeremy
...
Posted by gardenglory (from Gainesville, FL) on August 20, 2007 at 11:50 AM:
yes it was, and I guess the tree dahlia itself has been there for many many years...always gets buds, from what they said, just never got to bloom, until last year, before a freeze would hit. It looked just like yours..same color and all.
...
Posted by JaxFlaGardener (from Jacksonville, FL) on August 20, 2007 at 1:47 PM:
Amazing, GGlory! That would certainly extend the growing range for the Tree Dahlia for others that may want to try it.
Thanks for the info!
Jeremy
...
Posted by Islandshari (from Kwajalein
(Marshall Islands)) on August 20, 2007 at 2:41 PM:
Great story Jeremy! Well written and very interesting! Nice start to the day!
...
Posted by gardenwife (from Newark, OH) on August 20, 2007 at 4:19 PM:
Zone envy's right, Dea. Jeremy, I had no clue there were species of dahlia that grew 30' tall...or even 10' tall. That's just insane! Fun article...I love your writing.
...
Posted by JaxFlaGardener (from Jacksonville, FL) on August 20, 2007 at 5:36 PM:
Thanks, all. It was a fun article to write.
Gardenwife - did you recognize the blown up version of your castor oil plant photo in the oil painting behind my photo in the bio? Thanks again for the great subject matter for the painting!
Jeremy
...
Posted by gardenwife (from Newark, OH) on August 21, 2007 at 7:01 PM:
Yes, I sure did! :) You're more than welcome, guy.
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Posted by 3gardeners (from Mableton, GA) on August 21, 2007 at 10:25 PM:
Loved the article. First one to catch my eye and to read. I was wondering though, would the plant benefit from flower cutting like a lot of Dahlias? Or is the season too short for any benefit? OR is it simply to tall to bother with flower cutting?
Thanks, I'm on the look out for one now!
Catherine
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Posted by JaxFlaGardener (from Jacksonville, FL) on August 22, 2007 at 1:51 PM:
In climates such as mine with winter freezes, the bloom time is so short that I'm not sure it would help to cut off the blossoms to extend the flowering time. In warmer climates, it might be of some benefit to dead head. It is still a fairly new plant for me. Some of the folks in the Dahlia Forum may be able to provide more expert advice:
I'm looking for more Tree Dahlias myself and hope to get some out of my propagation attempts this Fall. I'd love to get in on some trading for Tree Dahlias, especially to obtain the white-flowering form and some of the double-flowering varieties.
Jeremy
...
Posted by bivbiv (from Central FL, FL) on August 25, 2007 at 6:51 PM:
Jeremy, I'm so glad you'll be contributing to the articles.
It arrived as a tuber tossed in as a “freebie” in a box of plant swaps from my DG friend, KayJones. As was my habit at that time, I potted up the tuber and set it aside without putting a label on it. I thought, because it was so unusual, I would surely remember its name. I have since recognized that my memory is not always as acute as I would like it to be. I have a few dozen UFOs (Unidentified Flowering Objects) sitting around in pots in my yard from roundups and propagations from friends. I’ve come to appreciate the value of providing a common name, or more preferably the botanical name, on a permanent label for a plant upon receiving it. I otherwise spend hours in frustrated befuddlement trying to ascertain what plant I have. If my angst finally grows great enough, I post a photo of the plant in the DG Identification Forum. I usually have an answer within a short time.
With a name in hand for the plant, I was able to research its cultivation requirements. The plant generally prefers part shade and is reported to grow about 8 - 15 feet high, though some observers claim to have seen the plant reaching up to thirty feet in its native habitat of the high Sierra Madre mountains of Mexico (where dahlia is the National Flower). The hardiness is usually listed as being limited to Zones 7 - 8, but it is growing very well in my garden, situated precisely on the borderline of Zones 8b/9a. 
