Found this cypress at a client's house, but am very unsure of the ID. If you know what it is can you tell me how you know? I see very few true cypress trees around here so do not understand the key identifiers between species.
Tentatively, Cupressus arizonica (not C. glabra [syn. C. arizonica var. glabra], despite that being much commoner in cultivation).
Still not fully sure, may be C. glabra after all. Can you get some more photos? A vigorous shoot with immature cones would be helpful. Is this in Washington State or DC?
I would have to take a second trip to the site. Is there a particular difference between species in the cone formation I should be looking for? One of the arbs on staff thought it might be the Gowen cypress, C. goveniana, and another forum I asked this on got a suggestion that it might be Tecate cypress, C. forbesii.
Flora of North America cypress key. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=108697
Are the small dots on the leaves in this photo what is referred to as resin-dotted and thus identifying the tree as arizonica?
Yes, I would say those are resin dots. Concluding it is C. arizonica I would base on the complete set of characters.
Thanks for the extra pic! That makes it Cupressus glabra after all. The Flora of N America took a very conservative approach to the genus including C. glabra in C. arizonica, wrongly so in the event as subsequent genetic evidence has shown they are distinct and not so closely related as previously thought. C. glabra differs from C. arizonica in having much more obvious white resin spots on the leaves (usually not present at all on C. arizonica). More details available here. The other two suggested by the Arboretum staff (C. goveniana, C. forbesii) don't have white resin spots either.
Yes, as it says on the Flora of North America page: This treatment, with seven taxa, approaches the more conservative end of a spectrum; anywhere from 6 to 15 taxa---species, subspecies, and varieties---might be accepted in the flora
