The effects of acid rain on plant growth vary depending on the local soils and other factors, but it is generally negative, inhibiting plant growth or even killing existing plants. The scale of the effect of acid rain depends both on its amount and the presence of buffering soil components.
Acid rain does not usually kill plants directly, although it does weaken the leaves of many plants. Instead, it tends to affect plants by limiting the nutrients they get or releasing toxins from the soil. These alone cause a plant to grow more slowly, but if it is combined with other environmental stresses, it can lead to death. Forests subjected to acid rain have been observed with browning and premature loss of leaves. Entire patches of forest are lost with acid rain as a contributing factor.
Acid rain has a greater ability to dissolve some soil nutrients than normal rain, so it can easily leach these nutrients out of the soil. At the same time, they can also dissolve toxic substances, such as aluminum, and expose plant roots to them. Some soils have particles of limestone or other substances that neutralize the acidity of the rain. Even in some of these cases, large amounts of acid rain or acid fog can overcome the protections.