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My Tree Dahlia (Dahlia imperialis http://davesgarden.com/guides/pf/go/56917/ ) grew this year very well with a stalk about 2 inches in diameter at the base and most of the way up the stalk, and lush green leaves. I think it benefited from the additional amount of sun it is getting after a diseased Live Oak tree was finally taken down by the city last year. However, when the Tree Dahlia reached about 10 ft tall, it started to lean like the Tower of Pisa. I intended to stake it up, but never found the few moments required to give it a support. Within a week or two after it started to lean, the Tree Dahlia eventually collapsed flat across the ground. I was concerned that if I tried to stand it erect again, the mostly hollow stem would snap at the base and it would be totally kaput for this growing season, so I left the stem to lay flat on the ground.
The growing tip of the Tree Dahlia made a 90 degree turn straight up and began to grow toward the sun. That portion of the Tree Dahlia is now at least 5 ft high and the flower buds are forming right on schedule and will be opening soon (and it will remain in flower until the first frost which usually comes in late December).
It has occurred to me that the toppling of the Tree Dahlia may turn out to be a good thing because it may provide me the opportunity to propagate more Tree Dahlias from the 10 ft portion of the stem that remains flat on the ground.
My plan is to dust the entire length of the stem with some rooting hormone, then cover the stem with good potting soil so that I build a mound of soil about 1 ft high that will bury the stem. I am hoping that new Tree Dahlia plants will spring up from the nodes of the stem and that the new plants will have the opportunity to root in the potting soil that is covering the stem.
Without any assistance on my part, two new Tree Dahlia plants have sprung up from the root crown and each of those plants is now about 2 ft high. I think that the rooting hormone and potting soil mound over the stem will encourage additional new plants from the nodes.
I don't think I have anything to lose by attempting this propagation experiment. My Tree Dahlia dies back to the root crown each winter and then emerges early in the spring around mid-March and typically sends up a single shoot from the root crown that grows to the final height of about 15 ft (unless it falls over as it did this year, or gets snapped off and doesn't get a chance to flower as it did last year due to a falling 40 ft limb from the city's diseased tree that crushed many of the plants in the same area of the Tree Dahlia).
I think about a foot of potting soil should be sufficient to keep the Tree Dahlia stem from freezing, but I may provide a blanket or twinkle lights or both on the coldest nights when the temperatures fall below 32 F for a few sustained hours on about a dozen nights between late December and mid-March.
Do any of you have any experience with propagating a Tree Dahlia from the stem in the way I will be trying?
All my previous efforts to propagate the Tree Dahlia from stem cuttings have failed. There were plenty of segments of Tree Dahlia stalk last year when the plant was crushed by the falling limb. I was hopeful that some of those stem pieces would root because the stem segments would send out a few new leaves, but then the stem piece would rot before any roots were formed.
I imagine the typical method of propagating a Tree Dahlia would be from root divisions, but I've not been successful in getting new plants from this method either. It may be that my Tree Dahlia (now about 5 years old) doesn't have a large enough root tuber to provide viable divisions.
I think if I can keep the buried 10 ft Tree Dahlia stem alive and keep it attached to the root crown (which will also be covered in about 1 ft of potting soil) without any rot occurring from too much moisture or soil organisms, I have a chance of getting several new Tree Dahlia plants that will arise from the stem nodes next spring.
Your comments, advice, suggestions or any information will be greatly appreciated!
The photo is of the root crown with two new Tree Dahlia plants currently about 2 ft high.
A whole D.I. sage in one post! All I can say, is Go Tree Dahlia, go! I think it's marvelous that the stalk aimed skyward again for you. How considerate to bloom at eye level. Fabulous looking buds too, and though I don't know about propagating from stalks, I bet someone will. Wallaby from across the pond did quite a bit of propagation. You might Dmail her or others will chime in.
Congratulations on getting to see such great growth after a fall to earth. Please post bloom photos if you get them.
Thanks, Pooch, for your comments and encouragement! My Tree Dahlia is, for me, one of the most thrilling plants in my hodgepodge botanical collection of one-of-everything that can possibly grow in my climate Zone. Perhaps my extreme admiration for D. imperialis is just the "dahlia on super-steroids" growth habit of the plant, or the "Jack and the Beanstalk" novelty of the thing, or maybe it is the year-long anticipation for the flowers of a plant that pops up early in spring, grows to gargantuan heights and then provides a brief but beautiful fireworks display of lavender flowers just prior to being knocked to the ground again by the first freeze, or a combination of all of these attributes.
It would be wonderful if I get a new D. imperialis jumping up from each node along the 10 ft stem. I could finally approximate a long-held desire to have a forest of Tree Dahlias!
Thanks for the referral to seek D. imperialis propagating advice from Wallaby. I will send her a Dmail to see if she has ever attempted a Tree Dahlia living stalk-rooting method for increasing her population of Tree Dahlias.
Propagating a tree dahlia is very easy I think. Before it is starting to freeze here, I cut of the stems. I'll take little pieces of them and put them in soil on a heatmat. And I put a cover over them. Nearly 100% is rooting. I don't know why it isn't working for you.
Sounds very good Leeuwtje and I wish you many dahlia trees as a result.
Jax a forest of "Jack in the Beanstalk" dahlias would be awesome. Here is an old thread covering the topic and how Willow did some cuttings. I don't know how warm your FL soil is this time of year, but maybe cuttings would be something to consider at some point. http://davesgarden.com/community/forums/p.php?pid=6562029
Still searching for Wallaby posts on the matter because I know she had started some shoots/cuttings. So far, no luck.
The fallen Tree Dahlia is now flowering! The flowers are about 6 inches across and seem larger than previous years, or maybe it is just because they are at eye level as a result of the Tree Dahlia's falling to the ground. It is very exciting and promising that the entire stem may root as I hope because the two suckers that sprang up from the root crown are already about 4 ft high and flowering also!
I thought I might lose some of the flowers because, clumsy oaf that I am, I accidentally knocked over the tallest flower stalk when moving a dead tree limb out of the area of the Tree Dahlia. The flower stalk bent and split open, but didn't completely break off the main stalk. I considered providing a splint using a chopstick and some twist ties, but never found the time. The flower stalk bloomed well (the flowers in the photo) despite the damage to the stalk. There are dozens of flower buds yet to open on this and other flower stems!
Jeremy - those tree dahlia blooms are beautiful. Great that you are able to get multiple suckers rooted along the fallen stem. I will definitely order a plant this coming year once they are available. 15 feet may be too tall for where I would like to plant them - Can I top it mid summer and have it branch out instead? A 6-7 feet specimen would be perfect.
Joann - Hope frost holds up until your buds open!
I am always on the lookout for late blooming flowers, and since we don't get frost until really late, this would be a great candidate. Has anyone had it blooming through December?
Our first frost usually comes in late December, right around Christmas, and the Tree Dahlia will keep flowering until the frost destroys the stems. It can even survive a minor frost for a few hours, but a sustained frost will cause it to die back.
I've not tried topping a tree dahlia to keep it short -- part of my amazement with the plant is from seeing just how tall it can grow! It does flower from stalks all around the top of the plant and not just the terminal stalk, so it could be that it would flower even if pruned back to control the height. It would be an interesting experiment to try. I am somewhat amazed that the suckers at the root crown grew so quickly and are already in bud with only a few months of growth and only about 4 ft high. If you cut the main stalk back on a Tree Dahlia late in the year (maybe around September?), it might send up short suckers like those that appeared on my plant.
I didn't get any flowers from my Tree Dahlia last year because during Tropical Storm Fay, a huge oak limb (about 40 ft long and 25 ft wide!) fell across the Tree Dahlia and that entire part of my yard from the street curb to my kitchen window (with fortunately no structural damage to the house) in August of 2008. That experience with the Tree Dahlia being accidentally topped out (and somewhat crushed), with a result that no flowers developed from the traumatized Tree Dahlia would tend to make me think that topping a Tree Dahlia might cause it to not flower.
Another option would be to deliberately create the accident that caused my Tree Dahlia to fall over and lie flat on the ground, then curve upward (to about 7 ft high now) at the growing tip. My very sandy soil apparently was not able to support the completely vertical stalk of the Tree Dahlia with the lack of firm footing also aided by several weeks of dry weather and a few windy days that helped to topple it. But you may be able to carefully dig around one side of the root crown to weaken the roots on that side and possibly also weaken the roots a little less on the opposite side and see if the Tree Dahlia would be able to fall over without breaking the stem at the base. I think if the "lucky accident" had happened earlier in the year with my Tree Dahlia, I might have had several flowering suckers coming up all along the main stem. The stem is hollow, much like bamboo, but unlike bamboo, the stem stays fairly green and flexible and doesn't get very woody in one growing season. You would need to be very careful not to snap the stem at the root crown in any attempt to make it deliberately fall flat. I let my Tree Dahlia fall over very slowly at its own pace (it took a couple of weeks to fall flat), and it managed to keep the stem intact and bent over at the root crown by a slight upheaval of the roots on the side of the root crown that was opposite of the direction the stem fell.
You are very welcome! I hope you will try a Tree Dahlia.
I happened to see the note by SierraTigerLily with her photo of her Tree Dahlia in Plant Files stating, "Time to cut them down again." I've sent SierraTigerLily a Dmail to see if she will provide some comments here on whether her Tree Dahlias flower after being cut back.
Nice work Jeremy and Joann. Those d. imperialis are marvelous and such survivors despite the fall/breakage of limbs. Lenjo, I'm pulling for a little bit more mild weather, or less wild, I should say, to give those buds a chance to open. Glad you both got to see them develop this much. Bloom or not, they are a fun plant to watch.
A long time ago I air layered some houseplant with a sphagnum moss blob secured along a stalk similar to the d.imp. I wonder if that would be worth an experiment along a leaf node.
An update -- we have warmer weather than most Decembers, with no frosts or freezes yet, so my toppled Tree Dahlia is still in flower. The experiment seems to be working for propagating the stem in contact with the soil! The several stalks that popped up from the root crown grew quickly and are still flowering, and new stalks are appearing at some of the leaf nodes. I gave the stem a good dusting with rooting hormone about a month ago, but haven't buried the stem yet, but did make sure the bottom half of the stem was in contact with the soil all along the length of the 10 ft stalk on the ground. The toppled stalk is now about 2 inches in diameter. I hope it works so that I have an entire row of new Tree Dahlias next year.
What does a Dahlia seed look like? In previous years, when I checked the seed heads that formed, I couldn't find anything other than some flat shreds that looked like wispy slips of wax paper with no obvious seed in them. Would my Tree Dahlia require another Tree Dahlia for pollination in order to make viable seed? The problem is probably that the first freeze comes and kills the Tree Dahlia for the season prior to the seed heads having time to fully mature (?) It would be great to be able to get seeds from my Tree Dahlia that would germinate. I could really have a forest of the Tree Dahlias if I could get a bunch of seeds that would grow new plants (and would have plenty of seeds to share!).
My poor D.i, is history. It finally froze on December 10th-full of buds but nary a fully opened bloom. It got so cold here those days and no snow cover. I am hoping the tuber are alive and well. I will dig in the spring. Joann
Great pics Jax! Lenjo I think your d.i. is well established so will return in your zone Lenjo. I got a dmail from my buddy in Vancouver BC and he's going to mail me a d.i. tuber when I get back from the SW. I am SO EXCITED I can't stand it! I just hope it will stay dormant til March :/
I'm glad someone revived this old thread! I can report success with my propagation efforts this past year for the Tree Dahlia. Several of the tall stems fell over in a wind storm in spring 2010. I buried the stems with about a foot of potting soil and powdered the styems with rooting hormone soon after the stems hit the ground. I got two new Tree Dahlias, both at the extreme tips of the former stalks. The original plant has now multiplied at the root crown to creat a cluster of about six tall stems. I added supports (bamboo poles) for the first time this year to keep the hollow stems from falling over as they grow taller.
I am currently intending to donate my extra Tree Dahlias to the Jacksonville Zoo and Gardens for their "Range of the Jaguar" display area. Since the Tree Dahlia is the national flower of Mexico, it should be appropriate there.
Jeremy - I ordered two DI from Annie's annuals and perennials last year - they grew well, but did not flower. They died back over the winter, and I left them as is. I have not seen any signs of growth yet. I assume that in your zone, your DI died back also? When did your DI start to form new growth for this year?
Thanks , I want the seeds to take to Mexico . The nurseries there don't carry much . The little town [ 45000 ] has 2 plant shops and can order things but I don't bother - either they don't come in or the wrong plant .
Seeds I can plant in different places [ I have 6 hectacres - bother has a 5 and a 30 hectacres ]
I want some color - Last 3 years - a pound of Calif poppy seeds each year - but birds , cows rabbits and ants probably ate them .
Hi, soils. My Tree Dahlias show new growth as soon as the temperatures are consistently warm here (around mid-February to early March). My Tree Dahlias are currently about 10 ft high and still growing. They are doing exceptionably well this year, possibly because for the first time I gave them some bamboo poles and wire rungs for support. They don't flower here until mid-November - sort of a shame since the first freeze usually comes late December, so it is a short period to enjoy the flowers. I would grow them, however, if I only got to enjoy the flowers for even a day!
If you start the D. imperialis from seeds, I would suggest keeping them in a pot and over-wintering the seedlings in a warm location for the first few years. You will probably have much better luck with DI if you start from tubers.
Jeremy - thanks for the information. Sounds like if my DIs are still alive, they would have sprouted by now. Slugs and snails are rampant here, so they might have eaten them as soon as they broke ground. I did bait a few weeks ago, but still no sign of growth. So, I think they are a lost cause. Can't decide if I am going to try again with buying new plants - I don't have good luck with seeds as I am a bad seed caretaker. 10 feet high - sounds like yours are doing wonderfully.
I never knew epson salt could be used to kill snails - I actually bought a box several years ago to use as a soil amendment, but never got around to using it. I suppose since regular salt kills them, epsom salt would too even though it is a different chemical composition. I'll give it a try. Thanks tonyjr.
There are 2 types of Datomaceous earth- the cheap one is for swimning pools and the other is for yards . It has been heated and breaks into little piecses . Also know as roach proof and flea power for dogs and cats .