<p>Abandoned agricultural lands carry a legacy of soils contaminated with heavy metals from previous land use practices. Phytoremediation using fast-growing trees is widely used method for ecosystem restoration by accumulating heavy metals in aboveground biomass. In Northern Europe, where 1.8 to 2.6 million hectares of abandoned agricultural land can be afforested, the knowledge of fast-growing tree species' phytoremediation capacity is still poorly studied. This study examines the phytoremediation capacity after 20&#xa0;years of afforestation of former agricultural lands with hybrid aspen plantations in hemiboreal Estonia, with a particular focus on the effects of different forest site type (<i>Aegopodium</i>, <i>Dryopteris</i>, <i>Hepatica,</i> and <i>Oxalis</i>) on heavy metal concentrations in topsoil and on bark and wood bioaccumulation factors. Soil, wood, and bark samples were collected from 24 sample plots to assess the allocation and accumulation of heavy metals in soil and biomass. The concentration of heavy metals in soil varied by site type, with waterlogged (<i>Dryopteris</i>) sites showing significantly higher levels of Cu, Fe, Ni, and Zn, whereas Cd and Mn were more concentrated in alkaline and dry (<i>Hepatica</i>) sites. The concentration of heavy metals in wood varied with tree size and age; smaller trees had significantly lower Cd, Cu, Fe, and Zn levels, while wood formed in the first decade of stand development showed higher concentrations of Cd, Cu, Mn, and Zn. Soil physical and chemical characteristics showed strong correlations with heavy metal bioaccumulation factors, particularly in bark. Soil pH negatively affected Mn bioaccumulation in all tree parts and Ni, Zn, and Cd in specific tissues, while soil P and available water content positively influenced metal uptake of trees. We found that the phytoremediation capacity of hybrid aspen plantations on former agricultural lands is controlled by soil properties and depends on tree size and age.</p>