"Sacha" wrote
[re balsam poplar]
In spring and early
summer the buds and young leaves have a strong fragrance of balsam
snip

http://www.pfaf.org/database/plants....us+balsamifera

Apparently, it can grow to 30 metres or so, so it's not exactly a
front lawn sort of tree but very good for the sinuses. ;-)

There's a row of what I've always taken to be Balsam poplars that I
often walk past and they do have a very pleasant fresh scent in Spring.
It's usually noticeable again in Autumn when the leaves start to turn
yellow. My hubby claims not to be able to detect it, but then he can't
smell the appley scent of sweetbriar leaves either. Another thing I like
about those trees is the way the slightest breeze is caught in the
canopy and makes a wonderful rushing sound which reminds me of the sea.
If I had acres to plant trees in I'd definitely have a few of these.

--
Sue