cypress knees

RonMartin(deceased)

Been doing a lot of reading lately on the Bald cypress. (Taxodium distichum ) Mostly bonsai publications.
They all seem to mention that the biggest charm with this tree is in its knees. Mostly I agree with this although I do think that what impresses me most about this specie is the foliage.
All the talk about the knees did get me to thinking though. Just where do they come from? Why are they there?
After much reading in both bonsai and regular horticultural publications I have come up with the three current official scientific theories. Not too sure which one is right but here they are. You take your pick on which one you like best.
1. They are there for gaseous exchange.
2. They help anchor the tree in the murky loose soil of the swamp.
3. They are a place for the tree to store starches above the water line.
All of these are good I guess but I do think that maybe it is a combination of all three. My opinion anyway.
But to this list I would like to add one more reason for them.
4. They make the tree look cooler than heck. I really like them.They are different and distinct to the specie.
This might not be the most scientific reason but it does satisfy my requirements ;o)
One thing I did notice in all my readingds was that the knees were only supposed to grow when the tree was in or near water. If it grew on the shore line then the knees were supposed to be on the water side. In the water they could pop on any side.
I am not too sure if I believe this.
There are a lot of cypress in my area . They are used extensively in landscaping here.
Maybe the cypress trees in South Carolina can't read. Not surprising considering our standing in the Sat scores ;o)
Seems like a lot of them will grow knees down here. No matter where they grow. Doesn't matter if the water is close by or not.
This tree is growing in the middle of a shopping mall parking lot. A good mile from the nearest water. ( the Ashley River)
Those funny looking things on the ground are in fact knees. This happens a lot in South Carolina. Landscapers are constantly cutting them off so people wont trip over them in the parking lots.
Not saying all the books are wrong. Just maybe the South Carolina cypress don't know squat about how they are supposed to grow. That is a bit embarrassing but I really don't know what to do about it.)

Attached Images

cy-01.jpg (57.6 KB, 115 views)

Advertisement

JavaScottC

Ron,
Interesting topic, Bald Cypress, as I have a couple, and the larger one has knees. I too have tried to find a reason they grow them, but to no avail, noone really knows why. Oh, sure, there is speculation, and grand assumptions, but no real clear answer. So I have just accepted the fact they do it, and let my obsessive nature go on this one. Perhaps the one in the shopping mall has an underground water source, and is letting everyone nearby know where the water is. Kooky. As for the knees growing in or near water, I keep mine in water after the freeze chance has passed all the way through until the freeze chance presents itself. Basically from spring to winter. And the knees are cool as heck.

Scott

__________________
Great, just what we need....another blogger



http://scottsbonsai.blogspot.com

RonMartin(deceased)

Be damned
The best answer to my question on knees came from a person that gets my newsletter.


"The true purpose of cypress knees is to produce tacky lamp bases for tourists.
Billy on the Florida Space Coast"

That is way too funny

Jerry Meislik

I love them too but my guess as to reason is .....?
Jerry

__________________
Jerry Meislik
Whitefish Montana USA
Zone 4-5
http://www.bonsaihunk.us/

meshako

I heard from a nursery owner in San Antonio, TX that the knees are sometimes a response to roots not getting air. He said that is why they tend to pop from underneath water. At this nursery, all of the cypress were putting up knees and he told me this was because a previous owner had laid down plastic sheeting to prevent weeds. The lack of air caused them to develop knees. I don't know if this would explain the knees forming in some landscape situations or not.

RonMartin(deceased)

I still think my item # 4 was the best reason )

Frogboy

I like your answer too, Ron. I travel a lot and have seen Cypress in nearly every environment in which they will grow, and the knees seem to have little to do with water unless it is just moist soil in general. Just this past week I was in Tampa and there was an area that had BC's planted in rows along the interstate. Yes, the interstate, yes, as landscape trees. They were on an elevated portion of the berm with water actually flowing away from them into a drainage ditch, and there were more knees than I have ever seen.

Go figure.

Frog

__________________
I wear hip boots for a reason.

meshako

Concur. Existing for the sake of coolness is probably the best explanation.

The only other motive might revenge on nearby humans because they do make great trip hazards and do interesting things to lawn mowers.

However, I always keep that plastic sheeting incident in that back of my mind because I want to try it on a bonsai scale sometime.

Speaking of different environments for cypress, the ancient ones that line the rivers in South Texas are among my favorite trees. The effect of hundreds of years of flash floods gives these cypress a much different look than the ones I see in the swamps further east.

Gary Marchal

Hi Ron....

Really?? What bonsai publications mentioned that the biggest charm with Bald cypress is it's knees?? Would you please post the publications and articles?



The question concerning the function of baldcypress knees has intrigued people for many years. There have been many speculations as to their function or functions. Knees were first thought to act as pneumatophores or breathing organs to secure oxygen for the root system. Correlation of the height of knees to the flooding regime, including the question of gas exchange, has been introduced as a function. It has been suggested that they assist in trapping soil and debris around the root system. A proposed function was that the knees add strength to the root system. Storage of starch has been attributed as another function of these structures. But, baldcypress appears to grow as well without knees as with them (Betts, 1945; Detwiler, 1916; Kramer, Riley and Bannister, 1952; and Mattoon, 1915), and since baldcypress is geologically old, the knees may be purely vestigal (Mancil, 1972).

Most early researchers believed that knees acted as breathing organs (Dickeson and Brown, 1848; Lamborn, 1890; Shaler, 1887; Wells, 1942; and Wilson, 1889). Others did not completely accept the fact that knees exchanged gases as there was no proof (Kurz and Demaree, 1934; Mattoon, 1915; Oosting, 1956; and Penfound, 1934). After extensive studies, Kramer, Rily and Bannister (1952) concluded that little gas exchange occurred between knees and the root systems on which they occur, and there was no evidence that they play an essential role as aerating structures for the roots. Cowles (1975) showed that cypress knees can be quite active metabolically. His studies concluded that knees account for about 5 percent of a cypress trees total respiration and he suggested the possibility of knees serving as metabolic exchange centers for roots buried in non-oxygenated muck. However, knees generally develop on the upper roots and not on the deep or lower ones which probably need oxygen the most. The process of respiration uses oxygen and releases carbon dioxide. This still does not imply that knees acts as a pneumatophore to furnish oxygen for the root system. Knee growth is apical, which results in a new orange-red bark. Microscopic examination of this new bark, which is about 1/8 inch thick, does not show any stomates, lenticels, aerenchyma, or organized pathways to support the concept that gas exchange is it's primary function.

A function of the knees has been postulated to be mechanical support of the root system. Normally the knee occurs at the place where the horizontal root takes a sharp downward bend which is a strengthening position. However, many knees do not occur at this location and thus, this explanation does not apply to them. But, Penfound (1952) said cypresses without knees and those on dry land are very resistant to wind-throw.

Microscopic examination of the knee tissure by Brown and Montz of LSU Horticulture Department revealed the presence of granules in the ray and vertical parenchyma cells. Small knees that were freshly cut were swabbed with an iodine solution which turned blue-black, indicating that a considerable quantity of starch was present. Cypress knees are therefore rich in starch, which can be changed back to glucose as required by the tree.

In conclusion,
1) The concept that baldcypress knees are pneumatophores has not been accepted experimentally, but the knees have been shown to conduct a small amount of respiration.
2) Knees, when present, may aid in strengthiening of the basal support, but they apparently do not function as anchoring devices for the trees since those without knees are wind-resistant.
3) Knee formation is considered to be a response to the aerohydroperiod. Based upon all studies to date, it is concluded that storage of starch is the major function of baldcypress knees.

Best Always

Gary Marchal

References:

Betts, H.S. 1945. Baldcypress. U.S. Department of Agriculture, Forest Service.
Detwiler, S.B. 1916. The Bald Cypress (Taxodium distichum); Identification and characteristics. American Forestry 22:577-585.
Kramer, P.J., W.S. Riley and T.T. Bannister. 1952. Gas exchange of cypress knees. Ecology 33:117-121
Mattoon, W.R. 1915. The Southern Cypress. U.S. Department of Agriculture, Forest Service Bulletin 272.
Mancil, E.M. 1972. An historical geography of industrial cypress lumbering. Ph.D. Dissertation, Louisiana State University.
Dickeson, W.M. and A. Brown. 1848. On the cypress timber in Louisiana and Mississippi. American Journal Science 5: 15-22.
Lamborn, R.H. 1890. The Knees of Bald Cypress; a new theroy of their function. Garden and Forest 3: 21-22.
Shaler, N.S. 1887. Notes on the Taxodium distichum or bald cypress. Mem. Museum Comparative Zoology 16: 1-15.
Wells, B.W. 1942. Ecological problems of the southeastern United States Costal Plain. Botanical Review 8: 533-561.
Wilson, W.P. 1889. The production of aeriating organs on roots of swamp and other plants. Proc. Academy Nat. Science Philadelphia 1889;67-69.
Kutz, H. and D. Demaree. 1934. Cypress buttresses and knees in relation to water and air. Ecology 15: 36-41.
Oosting, H.J. 1956. The Study of Plant Communities; An Introduction to plant Ecology. W.H. Freeman and Co., San francisco and London.
Penfound, W.T. 1934. Comparative structure of the wood in the "knees", swollen bases and normal trunks of the tupelo gum. American Journal of Botany 21: 623-631.
Cowles, S. 1975. Metabolism measurements in a cypress dome. Masters Thesis, University of Florida, Gainesville.