How to … Cite a herbarium
Citing the herbarium in which a particular specimen is deposited is important to adequately reference, e.g., a holotype. This is because it is common (and best) practice to deposit duplicate specimens with multiple institutions.
Most journals allow or prefer a herbarium code to be used when specifying a herbarium. Standard codes for all registered herbaria may be found in Index Herbariorum, an online registry of herbaria maintained by the New York Botanical Garden.
Note that the the preferred term in Index Herbariorum is herbarium code. It is not necessarily an acronym or an abbreviation, even though those terms are sometimes used.