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Acid deposition is a major biogeochemical driver in forest ecosystems, but the impacts of long‐term changes in deposition on forest productivity remain unclear. Using a combination of tree ring and forest inventory data, we examined tree growth and climate sensitivity in response to 26 years of whole‐watershed ammonium sulfate ((NH₄)₂SO₄) additions at the Fernow Experimental Forest (West Virginia, USA). Linear mixed effects models revealed species‐specific responses to both treatment and hydroclimate variables. When controlling for environmental covariates, growth of northern red oak (Quercus rubra), red maple (Acer rubrum), and tulip poplar (Liriodendron tulipifera) was greater (40%, 52%, and 42%, respectively) in the control watershed compared to the treated watershed, but there was no difference in black cherry (Prunus serotina). Stem growth was generally positively associated with growing season …