I gotta bring this thread back from the dead. I've used stem rub to confirm identity of my keepers after cloning or if I'm unsure I might have mixed them up. I can EASILY tell which of my keepers it is from a simple stem rub.
No, stem rubs don't smell exactly like the final flowers. BUT...there is definitely a distinct stem rub to many cultivars, and this can be very helpful.
Here are my observations from cultivars I've grown:
SFV OG (Cltvtd TC): piney, "green"
Cherry Pie (Sac Dispo): Bitter Cigars, Burnt something (Flowers are very similar smell but with cherry fuit)
Purple Urkle (Santa Rosa Organicann pre-64): Piney, bitter cigars, menthol (Flowers are grape candy and skunk)
Gushers (PCG): Piney, bitter cigars, slight menthol (Flowers are grape, pine, GAS, incense)
Ultraviolence (PCG): cheesey lemons, a little spice (Flowers are cheesey, urine, orange juice vomit ammonia)
Chem 91 (Harborside Farms): Pickles, lemon, pine (Flowers are solvent glue, lime, pickles, garlic)
Headband (Elemental Wellness Nursery): Lemon, pine, herbal/medicinal (Flower is floral, herbal, lime)
Legend OG (PCG): Same as headband
Tahoe OG (Roots Nursery): Same as headband
AJSD (PCG): Citrus and holiday spice, quite lovely
Obviously, there is a limit to what you can do with a stem rub...It's not very easy to tell the difference between very closely related cultivars like different cuts of OG/headband/idk maybe fake headband. It also depends on the stage of growth. My observations are usually on a smallish plant or clone; I like to rub pretty vigorously on a smallish branch that is still green, but has some stiffness to it...usually ~0.25-0.75 cm...I think the bigger or smaller stems don't smell as reliably.
Strangely, it seems like a slightly mentholy pine stem rub might indicate grape, as I've noticed that similar characteristic to the stem rubs on Grape Ape, Purple urkle, and Gushers.
-gNs