Small tree in downtown Tucson, Arizona. Not a native plant. Extreme cauliflory. Fruits (not shown in pictures) are small, hard drupes. Looking at the tree one would think Rhamnaceae or Oleaceae. But not one I've ever seen.
could it be in the myrtaceae? something like Syzygium? the green open flanges and the naked stamens seen to suggest that? or am I way off? a picture of the whole tree and some leaves would be great
Yes, Myrtaceae was another family I've been looking at, but I have not been able to find any Syzygium species with yellow flowers. Other members of the family are mostly tropical (exception being Eucalyptus). I'll try to get some photos of the leaves posted soon.
That street plan actually does document the area where I saw the trees but it is not one of the trees listed. here are some photos of the fruits (I believe from last year).
The leaves are not fragrant. here’s another photo showing the two small seeds that are found in each fruit:
I was wondering, but I should have believed you enough to stop looking at Ficus. I hope somebody gets this; I'm very interested.
Is a Celtis species possible? Leaves look a bit like it, less sure with the fruit though (Celtis fruit usually pendulous on longer stems).
Of ones with very short peduncles, there are Celtis pubescens, C. iguanaea - hmm, I thought I had two, but they're synonyms. Not much in the way of description for either one, no flower photos that I can find. Accord to Celtis - Trees and Shrubs Online, for the genus in general, "Staminate flowers occur in the lower leaf axils of one-year-old branches or grow directly from the stem (cauliflorous). Female and hermaphrodite flowers occur together in the upper leaf axils." It does say at the bottom of the page, though, "Fruit a drupe, solitary on a slender stalk, one-seeded." @teague has said two small seeds. Do you think some species might be different? Or do we rule this out? Just for the record, Celtis seems to be in the Cannabaceae family now.
If it is a Celtis, it is neither of the two native species to Arizona, nor is it C. iguanaea, that one I’ve actually seen in the wild as well. The flowers did remind me of Guazuma flowers (same family), but again not quite right...
Not same family, and not even the same immediately before now that Celtis is in the Cannabaceae family; Guazuma is in Malvaceae. The fruits looks very different too, from what you've shown.
I was looking through this list Maricopa County Urban Tree Selection Criteria (the county north of Pima county where Tucson is located), looking for this plant. Got to the last entry--Xylosma congesta. What about that one? https://webcms.pima.gov/UserFiles/S...n/10_23_2018_ Maricopa _Co_Tree_Selection.pdf File:Xylosma-congestum-20071001.jpg - Wikimedia Commons
Well, I was certainly not going to think to look in the Flacourtiaceae family. The description in Xylosma congesta in Flora of China @ efloras.org seems to not contradict anything we see in the photos here, but it doesn't mention cauliflory, which would seem to be such a prominent characteristic. There are several photos here, though: UFEI - SelecTree: A Tree Selection Guide (calpoly.edu). I see this listed as X. congestum several places, but Xylosma in Flora of China @ efloras.org seems very clear on the matter:
I took an interesting tour of cauliforous trees on the Web, but I think I still need to read a book. I had never thought about why it might exist--ground based pollinators who don't fly can visit. We also sometimes see flowers open on the trunks of flowering cherry trees.
Wow, I believe we have a winner! I see that there is a collection of this plant from the University of Arizona (Tucson) campus, so that have it in cultivation there, which indicates it could also grow downtown. The Calpoly site says this: Flowers and fruit are rarely produced. Good as a hedge or large screen, or can be trained as a tree. So I guess I got lucky. Also, odd that it was placed as a Croton at one point.
I don't know this genus at all, but I wonder about that statement. For one thing, this species does seem to have male and female flowers on separate trees, so the the male trees would not be producing fruit. I was going to say that as a hedge, the stems might be trimmed off where flowers would be, but that shouldn't affect the cauliflorous areas. That seemed to be the least of its troubles. Flacourtiaceae - Wikipedia says that the family "Flacourtiaceae is a defunct family of flowering plants whose former members have been scattered to various families, mostly to the Achariaceae and Salicaceae. It was so vaguely defined that hardly anything seemed out of place there and it became a dumping ground for odd and anomalous genera, gradually making the family even more heterogeneous.[1] In 1975, Hermann Sleumer noted that "Flacourtiaceae as a family is a fiction; only the tribes are homogeneous". The efloras.org pages I quoted above have it in this family, but Wikipedia says Salicaceae, in with the willows, whereas Croton is in the Euphorbiaceae family. Note that the genus Croton is not the same as the plant with the common name Croton, which is Codiaeum. You should see the list of synonyms for Croton at Croton (plant) - Wikipedia. But then on that Croton page they have a photo of Croton petra, which some other page says is a Codiaeum. I wonder if Xylosma is the only genus in Salicaceae that is cauliflorous. Here is a page that has a photo of the female flowers. Xylosma - efloraofindia (google.com)
Hi @teague. Could you contact whomever planted the tree in question to ask what it is - or to confirm your assumed identification?
Yes, it would be a good idea to try to contact someone to get more info. There are quite a few species of Xylosma, if that is the correct genus. I could not find any street tree list on Tucson city Website. I would normally be in Tucson at this time of year, but we cancelled our trip this year. After looking through these tree lists, it's surprising how many can be grown in the desert.
This is bizarre...so frustrating. See above..Friday 4th December I found a wonderful link..... "Downtown comprehensive Street Tree plan - City of Tucson" https://www.tucsonaz.gov/files/pdsd/Downtown_Street_Tree_Plan.pdf It was pages long and had several street maps marked with trees and lists of those trees. Now it refuses to open again. @teague. was obviously able to open it. "That street plan actually does document the area where I saw the trees but it is not one of the trees listed."
Oh, yes it still works. I did see that, but it is primarily recommendations and is from 1998. There seems to be some current tree mapping on the last page, but hard to decifer and seems incomplete and is from 1998. But if you try to search from their main Webpage I can't find anything more current.
According to the Flowering Plants of Australia (Families of Flowering Plants of Australia), plants in Flacourtiaceae can have: "Inflorescences terminal, axillary, cauliflorous or ramiflorous, consisting of racemes, panicles, cymes or solitary flowers." I have found several papers stating this. I am guessing that this statement is for plants grown outside of their native habitats. The plants probably flower and fruit quite well in their tropical homes. The 3 trees are planted in a small area between a road and sidewalk, probably planted by the city. I could reach out (and may) to the city when I have some more time. However, the fact that both U of A and ASU (phoenix) have records of growing this particular species on their grounds is a pretty good argument for the plants being X. congesta. Pictures of the flowers that I have found are near identical matches. Xylosma congesta (or any Xylosma species) was not on that list. But it was several decades old.
