This study compared growth of hybrid poplar in relation to soil mounding and mechanical weed control on a former agricultural site under boreal climate in order to assess optimal management scenarios. Height and basal diameter growth of 2 clones (Populus maximowiczii × P. balsamifera [915319] and P. × euramericana × P. maximowiczii [916401]) were evaluated after 3 growing seasons in 2 mounding (mounded, unmounded) and 4 weed control treatments (0: no weed control; 1, 2, and 3: 1, 2, or 3 passes of mechanical weed control). Net photosynthesis, stomatal conductance, soil temperature, and percent cover and height of competing vegetation were measured to explain the effects of soil mounding and weed control on tree growth. Two passes of weed control increased growth of trees by 23% in basal diameter and 12% in height, while mounding had no effect on growth. Both mounding and weed control reduced the cover of weedy vegetation, which was negatively correlated with growth of clone 915 319. Mounding did not increase mean soil temperatures in spring and even reduced them in the fall, while weed control had no effect on soil temperature. Finally, mounding significantly reduced the frequency and severity of damage (girdling) caused by voles during 2005–2006, especially for the plots that were not weeded.