Tier 2 Video Discussion: Bald Cypress Primer

The featured tree is not a bald cypress (Taxodium distichum), it is a pond cypress (T. ascendens). I took an informal poll of Mirai subscribers here in Louisiana, as well as others in the local club, we all agree on this point. There are those who will classify pond cypress trees as a variety of bald cypress (T. distichum var. imbricarium), but in either case, you’d call it by its common name.

There are several differences that can be distinguished between mature trees in their natural habitat (height, knee shape, bark color, base shape), but in a pot, we’re left with leaves and cones. The leaf growth of the tree in the video are erect instead of spreading, and the layout of the smaller leaflets are imbricate (clumped to the stem) rather than distichous (spread out flat). While the lower branches do have more distichous leaves, they’re the exception to the mass of leaves at the top. T. ascendends can exhibit this leaf structure on some immature branches, while T. distichum would not have such a mass of imbricate leaves at the top.

You can check with Mary Madison on the type of tree you’re working in the video since she supplied it.

I’m willing to eat crow on this. Perhaps there is something about the Oregon climate that is affecting the shape of the leaves. Early research (1800-1900) on the trees postulated that the single species of bald cypress would vary leaf shape based on its soil, rather than stating that the trees were two different species. Since Mirai is 1700 miles from the nearest natural habitat, there may be something to this (and that would be really cool to know).

Another characteristic of bald cypress which is, by my research, often stated incorrectly, is the function of knees. The bark of knees do not have enough lenticels to fix oxygen for the roots. According to the book “Baldcypress: The tree unique, the wood eternal” by Brown and Montz, the knees contain a great deal of starch. It is concluded by the authors that starch storage is the primary function of knees. Excess plant sugars are combined into complex carbohydrates, starch, and are stored in the parenchyma cells which makes up the bulk of a knee’s mass. In times of stress, the tree can call upon this reserve for energy.

Finally, as to getting bald cypress to grow knees, the following technique works best on newly collected trees. I recommend flooding the tree completely from the point where the leaves are set (mid to late March in NOLA) until the leaves change color in the fall. Water should completely cover the soil, and a little more, for all these months. The tree will begin to react when the water is depleted of oxygen. Use insecticidal oil to keep your mosquito population down. Then let the roots drain when watered during the Winter months. Also important: Don’t cut on the tree. This is another reason to do this with freshly collected trees.

The side-effect of this technique is a fattening of the roots and base of the tree. Long before you see knees, the base of your tree will change drastically. Inundation causes a significant change in the production of gibberellins, cytokinins, and ethylene. The first two hormones crash, while the third spikes. Then the root tissue forms aerenchyma; hollow tubes used in the transport of gasses. People who have worked with bald cypress both flooded and not, will notice that the flooded tree’s roots are softer, thicker, and have a spongy texture.

I’m about to start a video project where I’m testing a variety of parameters on a couple dozen trees. The research will take me a few years to complete. I’ll be documenting the changes in each group as well as attempting the same techniques on seedlings. Some people say you cannot get flared bases unless you harvest the tree from the swamp. Got 10 years? I think I can get you a flared base if you start with a seed. At least, that’s one of the goals of my project.

Anyone wants to know more? Check out my channel on YouTube, the link is in my profile.

I really really want to discuss this video further. I want opposing views. Let’s hit this topic Mirai-hard.

(EDIT: Wording and spelling)


Incredible description, incredible information, incredible observation skills and incredible delivery. You’re a good man, my friend. Not only is it difficult to go against the information someone you respect is giving you, but making the decision to make your observation known is hard. You went about this correction in the most respectful way possible. Taking the time to do your research, converse with other practitioners about their observations, do more research and then deliver the information as concise and clear as you have here shows just how much you care about the information being passed around the community. I typically get bothered when students pick out every time a sensei contradicts himself or try to go against the products or information being passed on, but this is how you do it if you’re going to. Awesome job. From the bottom of my heart, thank you for putting in this kind of work for the gain of everyone else.


Hey Bill… I agree with 98% of what you are saying. I am one of the folk’s that doesn’t believe you can get a tree with flare without collecting. I think you can absolutely get a bigger base (a very good base for Bonsai) but not flares that go up the trunk, that for me are one of the most distinguishing features of the species, with container growing.

You are 100% correct about this being T. ascendens and not T. distichum. For me, Pond cypress are very different trees than baldies…less hardy and less vigorous in addition to less desirable foliage and fluting…and far less winter hardy. I do have to say I love some of the really old stunted pond Cypress that come out of southern fla. like the one in this video. I also find the finer foliage to be a little more believable for smaller size trees.

Sorry this thread didn’t take off like you hoped.

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I was exceedingly glad to hear Ryan talking about developing bald cypress as a flat-top. They can certainly be developed in other ways, but the flat-top style is so typical of mature specimens. One of my students recently took some rather negative criticism on a flat-top cypress he developed and posted online. I believe the comment was something like, “flat-tops only belong on Marines.”
As someone who has been growing bald cypress bonsai for a number of years, I thought I would contribute my experience with growing knees from collected bald cypress.
If you are fortunate enough to find a bald cypress with a knee or knees that can be collected with the tree, it is usually so out of scale with what will be a finished tree that it is not worth collecting because it would look ridiculous. Most of the bald cypress that we collect is growing in swamp or marshland as opposed to dry ground. And cypress growing in a swamp or marshland develop much larger knees than cypress growing on solid ground. Simple observation will tell you that.
I will not try and debate the function of the knees. There have been six different hypothesis formulated on why bald cypress develop knees and every one of them has either been disproved or called into serious question. All of my research points to the fact that, despite over 200 years of trying to figure it out, we still do not really know (with certainty) their function. However, I have not been nearly so concerned about unraveling the mystery of their function as I have about how to replicate their development in bonsai.
One of my former bonsai students, Wayne Greenleaf, began experimenting with growing knees in the early 90’s. His experiments were designed to try and artificially duplicate the rise and fall of water levels commonly seen in our local swamps around New Orleans.
His efforts inspired me to follow suit, but along a slightly different track. Wayne totally submerged the soil in which the trees were planted. The first thing one must understand about cypress knees is that they form relatively quickly. You may get as much as six inches inches of growth in height in a single growing season. Now cypress knees that form in the swamp will typically grow anywhere from 6 to 36 inches in height. The largest recorded cypress knee was 14 feet in height! When Wayne developed his cypress knees in total submergence, the knees grew quickly and grew tall.
As stated earlier, one has but to observe the difference in the height of cypress knees on trees growing in the swamp and trees growing on solid ground. In addition, not all cypress trees grown on solid ground develop knees. I also don’t know anyone who has grown cypress knees in a pot without keeping the root mass saturated. Therefore, my track was to grow collected cypress in water, but not submerge the soil at any time. The best illustration I can give you is to describe my most recent bald cypress project, pictured above.
The tree was collected as a cut stump in January, 2015. The width of the buttressed base is 15 inches at the soil level. The height of the tree is currently 38 inches. Immediately after collecting, the tree was planted into the bonsai container in which it is currently potted. This is not the final container, but was of an appropriate width and depth when I collected the tree. I then set the potted tree in a large plastic mortar tub and filled the tub with water. The depth of the bonsai pot was such that when the mortar tub was completely filled with water, it was still below the rim of the pot. My method is to keep the root mass in water, but not let the water exceed the soil height. In fact, I usually keep the water level about one to two inches below the soil level on collected cypress trees.
These trees take in a lot of water and I refill the tubs daily during the heat of summer, when transpiration is at its height. I conduct minimal pruning on the shoots that pop on the trunk and allow the apex to grow unhindered. I do this for three to four growing seasons, while providing ample fertilizer on the soil.
The tree must first become root-bound in the growing container. Second, it must be grown in water constantly throughout the three to four-year period. When the knees develop (and they develop all at the same time), they are much smaller and in scale with the rest of the tree. The tree pictured above has a total of 23 knees, ranging in height from 1/2 inch above the soil to the largest, which is 4 inches above the soil. Most of the knees are about one to two inches high.
If there is anyone interested in more information about this process, such as soil type, water ph, fertilizer, etc. just let me know and I will be glad to share.


Good to see you here @Katsura45 !!!

If anyone wants to know where I get my information, Katsura45 is currently my go-to source. I met him about 25 years ago when I was just getting started in bonsai. I still remember my first meeting and some of the advice which I received.

That 23-knee tree is outstanding! I’m going to continue Wayne’s approach to growth; flooding and draining. He was another character from back in the day whose advice I sought out and appreciated.

As for the function of knees, I’ll have to debate the point with you, Katsura, the next time I see you. :smiley:

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Dear @Katsura45

Yes please share more information about this process, such as soil type, water ph, fertilizer, etc.

Very interested to test this out



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I’m sure that I am not the only one who has been successful growing knees on bald cypress in bonsai culture. But as far as I know, no one else has written much about it. One thing that I have seen practitioners do to try and create knees is to take small roots, pull them above the soil surface and wire them together to form a loop. There are several tree species native to swampy areas that naturally form “looping roots”.
However, a looping root is not the same thing as a knee, nor can you form them in that manner. So I hope that this information is helpful. Before we get into the method that I use to develop knees on bald cypress bonsai, let’s talk about a couple of topics relating to knees.
There are two areas of discussion: first, the purpose or function of knees and second, what causes them to form. Now it may seem like the two are synonymous, but in truth, they are very different. The first area for discussion, the purpose or function of cypress knees, is one that is still up for debate. Various hypothesis have been postulated on the purpose or function of cypress knees: oxygen intake for the tree during extended periods of high water, increased structural support in unstable soil, vegetative reproduction, a means of releasing methane, a means of accumulating nutrients from the water, and as a mechanism for storing carbohydrates. A few of these have clearly been disproved, such as a means of releasing methane and that their function is for vegetative reproduction. As for the others, there is still no definitive explanation for their purpose.
There have been many research studies conducted on this topic. And like so many other topics of research and study, one can find studies to support or disprove just about everything. The fact is, that after 200 years of research, there is still no universally agreed upon purpose for cypress knees.
Whether their function is aeration of the root system, storage of carbohydrates or something else entirely, is not as important for us as bonsai artists as to know how to create knees, keep them in scale with our bonsai and keep them alive. I will talk about all three. This brings us to the second area for discussion: what causes knees to form in bald cypress. There are a couple of pieces to the puzzle that you first must have. First, research has confirmed that bald cypress trees will begin to form knees when they are about 12 years old. So, first and foremost, you have to secure a cypress that is at least that old, if not older. Second, cypress knees only develop from surface roots.
They do not form from roots that are deeper in the soil, but strictly from the topmost roots. This is great news for bonsai artists in that it means that we can develop knees while growing our cypress in bonsai containers. Third, I have observed that knees tend to form ‘en masse’ when a tree is in pot culture. That is to say that, if a tree develops 10 knees, they all tend to form in a single growing season and will grow quite rapidly.
Let’s think about when we see and, more importantly, when we do not see, cypress knees developing. Most obviously, we see cypress knees developing in the swamps, along the banks of slow moving rivers and bayous. In this type of environment, knees will average between 6 to 36 inches in height, although they have been seen in some areas growing 8 to 10 feet. The record is 14 feet.
We see them develop on dry land where the water-table is within a few feet of the soil surface. In this type of environment, we will typically see knees that range from 2 to 12 inches on average.
We do not see knees develop on cypress growing in deep water.
We do not see knees develop on cypress growing on high ground.
And we do not see knees develop in pot culture. The one mitigating factor that results in the formation of knees is …water. And water at the right depth in relation to the roots.
Bear with me while I share a few observations regarding bald cypress bonsai. There have been many of my students, peers, teachers and mentors, during the past 40+ years that have developed excellent bald cypress bonsai. But only one developed a cypress bonsai with a knee and that was Vaughn Banting. The tree below was one of Vaughn’s and is now on display in Washington D.C. It is the one cypress he developed having a knee. It served as a model for all future flat-top design in cypress and I recently learned through Ryan’s video on bald cypress that the knee on this cypress has died. The tree is in good health, but the knee died. I found that very interesting and feel that it confirms a theory I have incorporated into the care of my own cypress to help ensure the health of my tree’s knees.
One of my former bonsai students and I began experimenting on developing cypress knees in pot culture about 26 years ago. The following practice for developing cypress knees in bonsai culture is a result of that effort. There certainly may be others who have achieved success by using variations on this theme, this is simply the method I use.
AGE – Make sure that you collect a tree that is at least 12 years of age. Here in the New Orleans area, we collect our cypress in January. Cypress tend to leaf out early in our climate and may already be leafed out by February. Today is January 6th and it is 72 degrees outside. It is not possible to know the exact age of a collected cypress, but if you talk to people in the nursery trade, they will tell you that bald cypress in the ground grow 1 to 2 feet a year. So I recommend collecting a specimen that is at least 12 to 18 feet tall, just to be on the safe side. You will have two to three years of growing in a container before knees will develop anyway, so you are pretty safe going with that height. If you are collecting a blunt and fluted variant, which typically grow in more open areas, it will be impossible to know the age. But if you have a buttressed base, you can be pretty sure that it is older than 15 years.
SOIL - All of the artists I know pot their cypress in bonsai soil (with the exception of my former students). There is nothing wrong with that. Bald cypress is an extremely adaptable species and will maintain vigor and excellent health in bonsai soil with routine care and maintenance. However, it is not conducive to developing knees. Let me correct that; it is not necessarily counter-productive to developing knees, but it IS counter-productive to maintaining their health. When I pot a newly collected cypress, I do so using Miracle Grow Potting Mix with Moisture Control. The moisture control components keep more moisture in the soil than other potting mixes. I use it during the knee development stage and at every repotting, to maintain as much moisture in the soil as possible for the health of the knees and the tree as a whole. After all, their native environment is in standing water. Cypress like an acid soil and you certainly get that with the vast organic composition of the Miracle Grow. You may certainly pot your cypress in bonsai soil and still develop knees through water inundation. It is soil inundation with water that causes knee development, not soil composition. However, once knees are created and you remove your bonsai from the water reservoir, bonsai soil will not retain sufficient moisture to ensure that the root mass remains wet throughout the day. It is my contention that excessive water absorption in the tissue is not only the reason cypress trunks develop a buttressed base, but also why knees form. And while there are plenty of roots below the surface to supply a cypress with water, if there is insufficient water in the soil to sustain the swollen tissue of the knees, (which only develop from surface roots) they will eventually abandon that root structure because the reason for its initial development no longer exists. This is why you do not see knees develop in routine pot culture. And this is what I believe happened to Vaughn’s cypress in the national collection. If you are determined to keep your cypress in bonsai soil, then you will need to maintain the bonsai pot in a water reservoir in order to keep knees healthy.
POTTING – I immediately pot newly collected cypress into a bonsai container appropriate to the trunk size and estimated finished height. I use a chainsaw to achieve a flat base in order to get it into a pot. I determine the front based on the nebari or buttress and anchor it into the container. Once the tree has been properly potted in Miracle-Grow Potting Mix, the tree and bonsai pot are place in a plastic mortar tub.
WATER – The mortar tub is filled with water up to, but not above, the rim of the bonsai pot. The water level is maintained daily throughout the year(s). It is essential to check the water level daily in the heat of summer. Between evaporation and the trees’ uptake of water and transpiration, the level may drop a couple of inches in a single day. Remember that water is the catalyst for developing knees. Once the knees develop to the desired height, remove the bonsai pot from the mortar tub or water reservoir.
FERTILIZING – Following the emergence of new growth, follow whatever fertilizing regimen you normally use. I use organic fertilizer as soon as leaves begin to emerge.
PRUNING – With the front of the tree established and potted in a bonsai container, I carve the trunk in back of the apex into an elongated convex shape. This facilitates the formation of callous tissue in such a way that there is no unsightly ridge along the edge of the large cut. The cut, once healed over, will maintain the curved contour of the trunk. Once shoots emerge, I determine which one will be my apical shoot relative to the front of the tree and rub off those that emerge in the immediate vicinity, to avoid competition for growth. Next winter, I may have to come back and readjust the carving at the back of the apex, depending on where my apical shoot emerged. However, from my experience, that is seldom necessary since they tend to pop at numerous locations along the edge of the angled convex cut I carve when the tree is first potted. You can select shoots that pop on the trunk for the future branch structure and begin to wire when the tissue hardens off, but do not prune the apical shoot. It must be allowed to grow unchecked. This will facilitate healing of the large cut, but more importantly will begin to generate a lot of roots due to all the new growth.
KNEE DEVELOPMENT – It is important to understand the following component of knee development: your tree must become root-bound. On a collected trunk, such as I have described, this usually takes 2-3 years. It is the combination of water inundation in the soil and the pot becoming root-bound that facilitates the formation of knees. Leave the tree in the water reservoir until the knees have reached a size that is proportionate to the tree. The knees will tend to grow quickly and may shoot up several inches in a single growing season. My observations would indicate that growth is retarded if not stopped completely when the bonsai container is removed from the water reservoir. You will be able to tell when the tree is becoming root-bound when you see roots growing in the bottom of the water reservoir. But maintaining the health of the knees is critical. Do not deprive them of the source of their creation – excessive water in the soil. In the heat of summer, you may find it necessary to place the tree back into a water reservoir, but if you use a potting mix that maintains moisture in the soil throughout the day, it will not be necessary.
I hope this helps. Let me know if you have more questions.


WOW Randy!! My head is exploding! I feel like I was at the best ever tutorial on Bald Cypress.
We are so grateful for information that has both been tested and proven to work. I have been relying on hearsay and old wives tales will little or no success. So maybe having factual and tested information will help me improve my game!
I am amazed at all the information available on this forum. I need to put some ice on my brain, but please do not stop with the knowledge that you have shared.
Do you have a web page or blog that we could follow?


I believe the thread has hit the stratosphere!! thanks all!

Thanks for the kind words. I’m glad you feel like you got some information you can use. I’m sorry to say that I do not have a website or blog to share. But as a newcomer to Bonsai Mirai, I look forward to participating in discussions and receiving as well as passing along information. That is the wonderful part about growing bonsai - it is a never-ending journey in pursuit of knowledge and skill.


It’s great to see you here as well Bill!
It is extremely satisfying to see you delving so deeply into bald cypress. It is truly a unique and fascinating species to work with. It is sad that more bonsai enthusiasts across the country fail to recognize and appreciate the legitimate nature of the flat-top style. I look forward to seeing you before to long.:crocodile:

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Randy, I would add to your instructions: Do not prune the tree. (or only do so lightly)

I’m following the conclusion of Brown and Montz (1986) that knees are a starch storage mechanism. If we prune on the trees, the tree must use its energy (glucose) to rebuild foliage. Pruning also reduces the tree’s capacity to produce sugar. If we do not prune the tree, the tree is able to become glucose-rich, combine it’s excess glucose into starch, and store it for later.

Letting the tree become root-bound and keeping the roots inundated are stress triggers. We’re feeding the tree to get vigorous growth, but we’re also telling the tree that life isn’t going to be easy. Its programming kicks in and knees develop. Christopher Briand (1990) challenges the Brown and Montz conclusion on the primary purpose of knees, pointing out that their hypothesis was never tested. (That may be due to Montz completing their book after Brown’s death.) Briand’s own conclusion that the function of knees may be a reaction to environmental pressures that no longer exist. Whatever the function is, the trigger for knee growth does appear to be stress.

I’m looking forward to seeing you at tomorrow night’s meeting. We can hash this out some more. Then, I’d like to have a word with you about schizogenous aerenchyma.

One more thing, when our bald cypress become root-bound in the mortar tubs, they tend to produce looping roots that pop up out of the soil. It turns out that the roots do the same thing in nature. Here’s a photo I took last year in our favorite swamp. I was out there with Dennis hunting for freaks.

And here’s one of the freaks (the tree, not the doofus):


That’s a great tree you collected!

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I love this thread! I was so happy to see it revived. There is so much good information. The gods have spoken!

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God doesn’t grow bonsai… God grows Sequoia… Sequoiadendron giganteum :heart_eyes: