Four, closest match I can find is Eupatorium semiserratum, or Chromolaena odorata? The difference is in the involucre bracts, but the flowers are spent and it's hard to tell.

What's the story with this plant? Did you find it, dig it up, and pot it? Just wondering if it's slightly wilted, compared to what it would look like in situ.

Excellent. Having the genus name, I found it : E. rugosum.

Yes, wilted, from two causes : a freeze some days ago, and uprooted shortly before photos. In water for posing purposes; I was en route to transplanting it, then thought to photo.

I have had two other species, different from each other and both very very different from this. Many of those, none of them now. This is a loner.

Started a new gardening thread:

Link:

Gardening plans for 2021

Four, what source are you getting genus and species from? Eupatorium rugosum has been Ageratina altissima for ages. I disagree with it being White Snakeroot , but it's your plant.

I did not explore Chromolaena odorata because the flowers in above photo hint at blue, similalrly in many other photos that I see when I explore it now. When I went for Eupatorium, I found the leaves that are shaped like mine : https://v3.boldsystems.org/index.php/TaxBrowser_Taxonpage?taxid=121555 

You see it differently, therefore we continue. About C. odorata I can say that its leaves in many photos differ from mine; nevertheless I do not exclude it from consideration.

There are no pictures on the link you gave and I have no idea what I was supposed to be seeing?

Ageratina altissima has glabrous serate leaves at the top by the flower heads, and a shorter flower. Your plant has longer flowers and entire, pubescent leaves near the flowers up top?

Ageratina would have lower cordate leaves. The leaves in yours are elliptical ovate.

This Houzz editor is a pain in so many ways. Not that it matters now, use of the link does not display the correct page because Houzz tacks on two non-printing characters when it is invoked. It works to use the URL by copying it. Does not matter now because the result of the smell test shifts us to Chromolaena odorata.

In addition to photos of C. o. leaves that are unlike mine, there are photos of leaves that are like mine, so, I am content with C. o., and I thank you.

Is this the link you wanted to post?https://v3.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxon=Eupatorium+rugosum&searchTax=

The link that Houzz made of the URL that you posted displays the desired page, as does the URL that I posted, which Houzz made into a faulty link that the site handles by displaying the search page instead.

Photo of a plant that was in my yard a few years ago. I always regarded the name as inappropriate because the flowers were odorless. I will know to crush leaves if ever it reappears.

I don’t understand what you mean by “The link that Houzz made of the URL”. I simply copied and pasted the URL. Houzz didn't do anything to it.

The editor made the URL into a link, which is usual behavior for programs that are HTML-aware.