Dendritic structures are widely present in nature, from snowflakes to dendritic cells. However, their formation mechanisms are unclear, which causes long unsolved engineering problems, such as lithium dendrites. Here a strategy to control the growth of dendritic structures by the selective adsorption of ions on crystal facets is reported. Silver particles are synthesized by galvanic replacement reaction and the growth anisotropy of crystals is regulated by changing the concentration of nitrate ions in silver nitrate precursor solution. At a low concentration of nitrate ions, messy branching particles are synthesized while symmetric dendrites are generated at a high concentration of nitrate ions. Molecular dynamics simulation suggests that the selective adsorption of abundant nitrate ions on low-energy facets promotes the prior growth of the high-energy facets, resulting in the symmetric dendritic structures. When the potassium nitrate is changed to sodium nitrate, similar phenomena are obtained, confirming the role of selective adsorption of additives in regulating the growth anisotropy of crystals.