Taxodium distichum var. imbricarium (aka Taxodium ascendens)
Cupressaceae
Pond Cypress has an inferiority complex…because its famous brother Bald Cypress (Taxodium distichum) gets all the fame. Different botanists classify Pond Cypress either as a separate species (Taxodium ascendens) or as a mere variety of the same species as Bald Cypress. Nothing could bore me more than worrying about the semi-arbitrary eye-of-the-beholder question of “separate species or not?” More a question of how you define a species than the soul of Pond Cypress. Whatever designation you care to give it, the tree has its own style and grace. Let’s start with what’s clearly visible. Pond Cypress differs from Bald Cypress by:
- Having the needles arranged all around the twigs and bent upward up against the twigs, which tend to be upright. (In Bald Cypress the leaves are in just two rows projecting at right angles to the twigs.)
- Placing less emphasis on “knees” and more emphasis on swollen trunk bases.
- Tending toward smaller stature, with overlap
What is more interesting are their ecological differences. If Pond Cypress is an evolutionary offshoot from Bald Cypress, into what different niche did it diverge?
If you Google the two, you run quickly into assertions of Pond Cypress in more-acidic conditions. Maybe so, but actual measured comparative data are lacking. Although Pond Cypresses often occur on acidic sites, they also grow on alkaline substrates. Around our area the two species occur as close as 50 feet apart with no likely difference in the soil and water pH. My guess is that substrate pH is not at the center of the species divergence.
Seems to me a more incisive interpretation comes from reforestation projects associated with the massive Three Gorges Dam in China. Researchers there studied the ecology of potentially useful wetland trees, including Bald Cypress and Pond Cypress, conducting physiological research on seedlings and young trees. To paraphrase a long story, the main ecological distinction revealed in China is that Pond Cypress is more adept at mobilizing, processing, and redistributing nutrient resources in its roots, giving this species more environmental flexibility. You might say Bald Cypress “wins” as specialist in its floody shaded narrowly specialized habitat, but step outside of that, and Pond Cypress deals more adroitly with diverse other habitats.
Bald Cypress grown in bright sun keeps its flat two-rowed leaf arrangement with no adjustment. But Pond Cypress grown in shaded places adjust its leaves into positions similar to Bald Cypress, or if too sun-baked and dry, can shed leaves temporarily, both abilities being examples of Pond Cypress’s ability to bob and weave. The environmental flexibility is why Pond Cypress occupies different habitats in different parts of its range, is no doubt why it tolerates acid and alkaline situations, is why it fares better in cultivation, and why it is more drought tolerant.
Around Palm Beach County, you seldom see wild Bald Cypress outside of a Cypress swamp, be it along a river or in a large seasonally (or always) flooded depression swamp where the soil remains submerged or soggy. Pond Cypress, by contrast, loves low slash pine savannas where the thin sandy soil dries periodically. Its usual neighbors are pines, not Bald Cypresses. Protection from drought and sun readily explain the clenched upright leaf arrangement. That arrangement may slow growth, but trees are patient, and some Pond Cypresses are far older than their relative small sizes suggest.
Occupying sunny open habitats, and upright twigs with upright needles makes for brightly illuminated branches, just what epiphytic bromeliads need. Many Pond Cypresses are home to large numbers of airplants, but most are small, as though something keeps them in check. Botanists David Benzing and Antoinette Renfrow back in the 70s found the constraint: Pond Cypress dwarfed by growth on especially poor soils turned out to have likewise dwarfed epiphytes. The tree starves its hitchhikers by having low nutrient levels in the stemflow along it bark.
To dig deeper: Benzing and Renfrow article
John Bradford
George Rogers
George Rogers
Dee Staley
Treasure Coast Natives 
Ann Yeend Weinrich
August 7, 2021 at 8:37 am
Hi, George.
Thanks again for another edifying botanical article! I checked on the meaning of that word, edifying, and found that it usually means inspirational or spiritual instruction – and since I spent much of my occupation leading students and adults into the actual physical swampy glory of cypress swamps, I decided it was a perfect use of the word.
Thanks also for reminding me how complicated the leafy life is – and now I am regretting I didn’t look more closely at all the cypress leaves I encountered.
I’m forwarding your article to my friend Sandy Austin, widow of botanist Dan Austin, who also wrote about cypress trees. I remember fondly them leading me and a few other swamp trompers through Fakahatchee Swamp hoping to photograph the famous epiphitic ghost orchids. Great cypress swamp memories. Just wish I’d looked more closely at the leaves.
George Rogers
August 9, 2021 at 8:58 pm
Hi Ann, How are the chickens? A few of you students of Dr. Austin are around, kinda nice. Love those cypress swamps…shaded and cool, no skeeters, novelties to see, owls hooting but not allowing a look!
Chris Lockhart
August 7, 2021 at 9:18 am
Nice, descriptive article on an allusive species. Thanks for describing the morphological and ecological differences and adaptations. I love seeing the many different air plants/ hitch hikers in cypress swamps. The Loxahatchee National Wildlife Refuge is a great spot. Various air plants are returning after a virtual wipeout from the Mexican bromeliad weevil. I never associated nutrients of the cypress with the presence of airplants. Thanks for the link to their research.
George Rogers
August 7, 2021 at 2:06 pm
Chris, For sure on the LNWR…went there multiple times this summer with my adult son, mostly trying to photograph birds. Hugely interesting what you said abut the weevil, wipeout, and recovery….I’ve wondered but never had a good look at relevant literature/records.
Greg Braun
August 7, 2021 at 9:31 am
Great post, George. The subtleties of these two have baffled me for decades, & I have to say, that up until now, I certainly leaned toward Pond cypress being slightly different only because of the localized condition where it was growing. Will look at leaf structure in the future!
Everything made logical sense until your last sentence. As far as I know, no Tillandsias extract nutrients from their host, so levels of nutrient flow in the bark are inconsequential. If indeed pond cypress have fewer epiphytes than bald cypress, a more logical explanation may be that because their leaves encircle the twigs, there is less bark surface area for Tillandsia parachute seeds to settle? Just a conjecture! Keep creating new plant posts – I always find them interesting.
George Rogers
August 7, 2021 at 1:57 pm
I don’t think pond cypress necessarily has fewer epiphytes than bald cypress, no data on that, and you do see epiphytes up high in bald cypress. What interested me is that on pond cypress a lot of the epiphytes seem stunted compared with those on other species, or as Benzing and Renfrow observed, stunted pond cypresses seem to tend toward stunted epiphytes compared with more robust pond cypresses. . A reason I sometimes link research to the blog is to make sure readers do not have to “take it from me.” There is a link to one paper on epiphyte vigor relative to the pond cypress bark nutrient content at the end of the blog. I added just before the link a snippet from the article mentioning the concern that the epiphyte does not penetrate the host.
Linda Grashoff
August 8, 2021 at 10:52 am
When I got to “some Pond Cypresses are far older than their relative small sizes suggest,” it triggered a memory. I saw these stunted trees and their attendant bromeliads myself when out with my husband, who was checking one of his research sites. I always enjoy your posts, George, even when they don’t mention David. 😉
George Rogers
August 8, 2021 at 7:41 pm
Thanks Linda! So nice to hear from you….I linked one of David’s relevant papers to the end of the piece…could scarcely have a better fit! The tillandsias on the pond cypresses are abundant and just plain cool…so totally worthy of David’s attention.
Louis Chinnery
August 8, 2021 at 6:52 pm
One other constraint to epiphytes in general is degree of sun exposure. Some need more sun than others. Could that be a factor here?
George Rogers
August 9, 2021 at 8:56 pm
Louis, for certain, thanks. It would be fun for somebody with nothing else to do (like me) to look into the distribution of epiphyte species on pond cypress.
Harvey Bernstein
August 9, 2021 at 8:22 am
Perhaps the smaller sized epiphytes have something to do with aerial nutrient flow: sparser leaves and reduced quantities of airborne organic compounds that the epiphytes need for growth are results of the drier, more open, sandier environment.
George Rogers
August 9, 2021 at 9:05 am
Well, something that could be tested separately. Benzing and Renfrow measured nutrient levels in stemflow. Also, recalling that there is no comparison made between the two types of cypress, it is not clear that the research was split between drier, more open sandier environments as opposed to wetter, more closed, un-sandier environments.