Compare to Senegalia nigrescens, aka knobthorn tree. Just a WAG!! Would be helpful to know where you are located as to what species might possibly be found in that location........

Location included would be helpful in any identification, also close up of leaves and stems or buds.

Possibly Zanthoxylum clava-herculis or southern prickly ash,

Yes: instead of showing the trunk three times you should show other parts of the tree in additional photos. What the rest of it looks like is the key to figuring out what it is.

It's not native to here (London, England) but an exotic planting. I haven't seen its leaves or flowers, but here is a photo of its form. Sorry for the poor quality image, the light was fading. I will take a better image tomorrow. Thank you for your suggestions.

There are no fallen leaves left. The buds are pretty non-descriptive, and none at low level for a close up. If we get a sunny day I will get my camera with a zoom and try and take some of the buds.

Try to find fallen leaves as well as any other spent parts there might be on the ground beneath it. And try to show close views of the winter buds.

I'm thinking Aralia, but I have no clue what species it would be

It would surprise me if it were Aralia.

Aralia spinosa, the largest species of this Genus barely reaches a diameter of 8" at maturity and is more of a suckering shrub than it is a tree.

It looks as floss silk tree

Trunk and branch form are wrong for genus Ceiba.

Bill probably identified the tree 8 posts ago:

https://www.bing.com/images/search?q=xanthophyllum+clava-herculis&qpvt=Xanthophyllum+clava-herculis&FORM=IGRE

Yes,

And if the yellowing leaves at the right, lower 3/4 of the last picture are from the tree inquired about, which they appear to be (pinnately compound), then all the more reason to think Zanthoxylum clava-herculis.

Is there a reason no one has guessed a Zanthoxylum like Zanthoxylum simulans?

OK looks like Zanthoxylum was misspelled as Xanthophyllum. Actually a different genus.

I just spotted that one too.

Probably my cut & paste of Xanthophyllum when searching and wiki brought up Zanthoxylum- clava-herculis without me correcting it in my copy clip.

I'll fix the above name in my posts.

Thanks dave!

Search using the right generic name seems to bring up more trunk shots:

https://www.bing.com/images/search?q=zanthoxylum+clava-herculis&qpvt=zanthoxylum+clava-herculis&FORM=IARRSM

Searching for pictures of simulans returns this result:

https://www.bing.com/images/search?q=zanthoxylum%20simulans&qs=n&form=QBIR&sp=-1&pq=zanthoxylum%20simulans&sc=8-20&sk=&cvid=DD575A48F2B04F8A9CBB97E0E8098D7B

Otherwise there's about 200 species in the genus.

haha!

Yes Embo, it works much better that way! :-)

Xantho and Zantho actually are both the "Z" sound but I'm not making any excuses, I messed up. :-))

Hello Bill,

Yes you seem to have the closest match of Zanthoxylum clava-herculis. Many thanks for your good eye and knowledge and thank you to everyone else for your input, it's appreciated.

http://www.foragingtexas.com/2008/08/prickly-ashtoothache-tree.html

Zanthoxylum rhetsa also seems to be a contender, but it definitely seems to be in the genus Zanthoxylum.

Next it's a matter of which particular species are present in outdoor cultivation in Britain at this time. Look for matches to your tree in arboreta and other publicly accessible collections where there is labeling present.

When visiting a friend in Texas, he had a saying, something to the effect of "everything in Texas will either stick you, scratch you or bite you". I don't remember the exact words but I can see now what he meant. :-)

And that's just the Texans - never mind the plants and wildlife.

Indians used it as a antiseptic and toothache numbing agent. And it works. What ever is in the bark/leaves it does numb the mouth. I've tried it along with my nephew. Just cut a sliver of bark off and stick it in your mouth. Just like being at the dentist office.

Steve, if you can find out who is responsible for the square they might be able to confirm the id. I've got a fast response from Kensington and Chelsea when I emailed about a tree I saw there.

Love bitter. Lettuce and cabbage hearts....

Thanks for the update Steve. :-)