It's kind of crazy how sounds and colors are mostly quantifiable and we have words for pretty much all the different qualities they can have, but smells can be so complicated and novel, and much harder to identify and describe.
i learned from a Plant Guy (can't say much about the program i was in for privacy reasons) who identified plants mostly by smelling them. A lot of plants have striking smells, and a lot of them don't smell like anything else.
Ailanthus altissimia trees have one of the worst smells ever. They smell sort of like peanut butter, like it's an oily, almost savory smell, but it's very heavily mixed with the smell of a musty basement. It is utterly foul.
Datura/jimsonweed smells so nasty I can't even touch the plant without my stomach turning. It shares some notes with ailanthus smell, but it's different.
Poison hemlock likewise is foul.
All parts of the kudzu plant have a very cloying artificial grape smell, but when you boil the stems/foliage it mixes with a smell of sweaty feet.
Pawpaw leaves smell extremely bitter. Oak leaves smell...oaky, and I didn't consciously realize there was an oaky smell until I was attempting to dry acorn flour in the oven and it smelled like that.
Plants in the mint family have a lot of aromatic compounds and different plants of the same species can smell like mint, basil, orange peel or even eucalyptus.
Black walnut smells like itself. It's all at once musky, spicy, sharp, and chemical-y but none of that actually describes what it smells like.
Hickory nuts have the most heavenly, buttery-sweet, almost maple syrup like smell you can imagine.
One of my favorite plants is Collinsonia canadensis, citronella horse balm, and its flowers have this unbelievably strong citronella smell.
Wild roses, at least the Carolina rose, have an absolutely lovely smell. I usually hate floral smells but this one is so pleasant. It's hard to understand in the era of always-blooming, unkillable, scentless Knock Out roses why roses were so revered in symbolism for so long, but the wild ones really are wonderful.
Speaking of smells, one of the worst smells I have ever encountered was chicken feather meal. It is basically ground-up chicken feathers and Farmer Family Friend was using it as a nitrogen fertilizer for his crops. I was spreading the stuff around and raking it out and god it was awful, I can't really describe it though.
Not all stinky smells are bad smells though. I have strong opinions on this. Horse smell is a very pleasant smell. Goat smell is also a pleasant smell, though not as much as horse smell.
