I actually just planted one earlier this week, Rhododendron canescens. It’s a bit small, so I doubt I’ll be able to report on the smell for a while yet.
More shrubs than trees for most people, but osmanthus seems to be missing from this discussion so far, tiny flowers, huge smell, I’d also add privets, some of which get to be trees. The hesperocyparis genus (Arizona cypress being the one most people have smelled, it’s nice, but some of the other species have lemony and other spicy, herbaceous overtones, really great smells), and Torreya taxifolia leaves smell like black cherry but way more intense, southern magnolias are great in bloom, ripe wild muscadines can be smelled from across a field, not a tree, I realize, but, well, they do grow on trees, so there. Ponderosa pine smells like caramel, and Arroyo sweetwood is strongly vanilla-scented. Eucalyptus is a given, and now that more frost-tolerant species are becoming available, I suspect they’ll start to see more landscape use out here in the east. For dried, seasoned wood, it’s really hard to beat red oak and juniper, though baldcypress, walnut, and sassafras are up there as well. As boy scouts, we always had a supply of “fat lighter wood” the old heartpine dug out from rotted stumps, the stuff is pure frozen turpentine and burns like nothing else–not many woods burn with black, oily smoke.
Devilwood is perfectly hardy here for decades. Had the purple tinted Kew hybrid for 25 years on the north side of the house in a foundation planting until a strange winter. Used sweet olive types in pots for customers. Several other Black Sea species were fairly hardy, came from Woodlanders.
The smell of chestnut blossoms remind me very much of stinkhorn mushrooms. Ive mistaken one for the other on a couple of occasions. Absolutely wretched.
Tamarillo has a pungent earthy smell that I kind of like. It reminds me of tobacco a bit. Its distant cousin so called dwarf tamarillo otoh has a scent that is more overpowering, almost like paint thinner of something.
Loquat blossoms are indeed lovely. They smell like vanilla to me. The smell doesnt carry much, you have to poke your nose right in there for the full effect.
Spicebush- Lindera benzoin- is a great fragrant one. Its very rare here, but I understand it grows like a weed in certiain points south. Ditto sassafras. I have some of both growing here.
wild pinkster azalea has to take the cake afaic for fragrant tree/bush. The first time I found one, I literally followed my nose to it. They smell like cinnamon, vanilla. Unreal how fragrant they are. And beautiful little bushes. They grow in very unforgiving places here- usually exposed rock facing south. Ive tried to dig a little sucker, but theres so little soil, it’s nearly impossible.
if you want to extend the discussion to non-woodies, chinese mt yam aka ‘cinnamon vine’ (Dioscroea batatas I think) and sea kale are two Id make note of. Sea Kale smells EXACTLY. like honey, Both easily fill a whole garden with their smell while in bloom.