Agarwood comes from trees in the Aquilaria genus, and oud is the resin-rich material and oil produced once one of these trees becomes infected and reacts by producing dark, aromatic resin. So the tree itself is agarwood, and oud is what you get from it once that natural process has taken place.

How the Resin Actually Forms

A healthy Aquilaria tree produces no oud at all, the wood is pale and largely scentless. Only when the tree is wounded, whether by insects, fungus, or deliberate inoculation on plantations, does it produce the dark, fragrant resin as a defence response, and this can take years to develop fully. Uninfected trees of the same species are essentially worthless for perfumery.

Why This Matters

This is exactly why not all agarwood produces valuable oud, and why age and infection quality matter so much to price and character. This is also why plantation growers now deliberately wound or inoculate young trees, essentially speeding up a process that would otherwise happen unpredictably in the wild over many years. Our complete guide to oud explains this process fully, and our complete guide to perfume has more on how raw materials become finished fragrance.