Can't really offer anything other than some guesswork, I don't have any hard scientific data. But T. ascendens grows in nutrient-poor ('blackwater') environments, while T. distichum grows in richer environments. That could perhaps affect cone size. Upright foliage - does it perhaps trap nutrients in rainwater better? Maybe, but I don't know.

Whether they are separate species or not has been argued over for the last 190 years or so. My personal preference is to consider it a species, but I don't have a very strong opinion on it, maybe subspecies might be better. Given the ecological separation (adaptation to different habitats), I'd say it is more than just a variety.

Resin

Goddamn man. You come through like water during a drought. Thanks again for the info.

RDAD Resin During A Drought. We could all use some from time to time.

T. ascendens grows true from seed, doesn't it?
Is the theory for keeping them the same species that T. distichum populations will independly show Ascendens characteristics when in certain stressed habitats, that the Ascenden-like trees survive better in those habitats but that the habitat would change the trees would evolve back to normal Distichum habit in a few generations?

These are long living trees, how does that factor into the theory?

The main reason some keep them as the same species is that in habitats with intermediate nutrient status, you get intermediate trees - with enough searching, it is probably possible to get a full range of variation from pure Baldcypress (B) at one extreme, to pure Pondcypress (P) at the other. But such a situation can just as easily be ascribed to interspecific hybridisation, as to lack of speciation.

How they would evolve with change in habitat isn't easy to tell - as you suspect, a several generation experiment has not been performed. Anyone with a few hundred (few thousand?) years to spare is welcome to try ;-)

What would be worth trying is some genetic analysis of the two across their ranges - if they are separate species, then a P from North Carolina should be genetically closer to a P from Louisiana, than it is to a B from North Carolina. If however it can be shown that B and P from North Carolina are each other's closest relatives, and ditto B and P from Louisiana, then they would be better treated as one species. As far as I know, this hasn't been tested yet.

Resin

And taxodium mucronatum too. It stays green much longer than T. distchum into the winter (evergreen in mild winters). Already, distchum are turning color or dropping leaves in Houston, a zone 9. I think T. mucronatum looks better than others but I guess that's matter of taste.

I saw a lot of t. mucronatums when I visited my daughter when she lived in Texas, Lou. I like the looks of them better than either t. ascendens or t. distichum, too. I've got the two I just mentioned plus a dawn redwood, and even when they were all growing in pots next to each other, I couldn't tell the difference betweeen t. distichum and the dawn redwood without looking at the identifying tag. The t. ascendens only looked a little different - the needles are thicker, but aren't pointing upward, at least not yet. I've also got a sequoia sempervirens 'Winter Blue' which has always been easy to separate from the others. 'Seems to me that dawn redwood/metasequoia glyptostroboides should be dawn cypress. :0
I think I'm going to order a t. mucronatum - may as well add it to the group!
Sherry

"Seems to me that dawn redwood/metasequoia glyptostroboides should be dawn cypress. :0"

Metasequoia is genetically closer to Sequoia and Sequoiadendron than it is to Taxodium (and Taxodium closest to Cryptomeria and Glyptostrobus). Equally, they're all in the cypress family Cupressaceae.

Resin

Sherry,

I can send you T. mucronatum seedling next fall! I collected hundreds of seeds and will be growing them in rootmaker products in the spring. I also collected seeds off weeping MC 'Setindo' that I could send a seedling to you but who knows how it'd turn out. And I can't tell dawn redwood from taxodium anyway. My brother is growing a bunch of dawn redwood and he doesn't know what to do with them as he paid a few dollars for hundreds of TINY seeds. They all look same to me as a seedling... He told me that it was pretty easy to germinate them. All he used was moist paper towel and they germinated right away...

I just want to know how the heck T. mucronatum stayed evergreen/semi-evergreen. They aren't that far apart from central Texas Bald cypress (distinctly different than the ones in East Texas and further east as far as the ability to tolerate alkaline soil in central Texas where limestone bedrock is)

We have grown some trees that when purchased were thought to be T. ascendens. The had the upright, more scaly needle foliage but grew out of it and now resemble T. distichum. Only one has retained T. ascendens type foliage.

T. ascendens also has a much more narrow growth habit.

Eric
Orlando,FL

Thanks, Lou, I may want to take you up on the seed offer next fall. When I saw so many growing in Fort Worth, I thought it was odd that they were growing in such a dry area, but then I looked it up, and that's their nature. So, I'll probably order one - Woodlander's carries them - and plant them on some dryer soil areas on my property. I'm finally seeing the light at the end of the tunnel for replanting my property since Katrina.
Sherry

Dawn Redwood should be easy to tell apart from taxodium in the seedling stage - Dawn redwood only has two seed leaves, taxodium has five (sort of like a pine)seed leaves.

Sherry,

Where are they in Ft Worth? I may want to check them out.

I can't remember, Lou. My daughter moved from there in 2000, and she drove us everywhere with me not knowing where we were - everything was a blur, I was so overwhelmed by the 'big city'! I only remember that they were growing in islands along a roadside next to a mall? and I also remember seeing a lot of them in and close to some botanical gardens which may have actually been in Dallas. The main thing I remember about them is that their foliage had more of a "weeping" look than bald and pond cypress, which I liked. I didn't know what they were at first, so when I got home I read up on taxodium and other possibilities, and I decided that they must be t. mucronatum. I hope I was right - these conifer type trees sure were pretty!
The main thing I remember about Texas was the scissor-tailed flycatchers I saw in a vacant lot across from the Denton, Texas, hospital when my grandson was born there. I'd always wanted to see one, and a pair plus one showed up! They looked awesome with those LONG tails!
Sherry