Abstract Poplars are traditionally cultivated on arable land, but other land types, such as forested land and forested arable land, may also provide significant opportunities for poplar plantations without competing with food production. However, these sites often have suboptimal soil pH levels that hinder optimal poplar growth, highlighting the need for improved establishment methods to enhance both survival and growth. This study investigates the establishment and growth of poplars (Populus trichocarpa and their hybrids) at forest land and forested arable land after application of wood ash, lime, and biochar using three different application methods: (i) amendment spread on the soil (Surface), (ii) amendment mixed with the soil (Mixed), (iii) amendment placed on the planting spot (Spot). Our findings revealed that wood ash and lime application almost double growth compared to untreated plants, 3 years after planting, and that growth increased equally independently whether wood ash or lime was mixed with the soil or applied on the soil surface while Spot application method resulted in overall lower growth than the Mix and Surface method. In contrast, biochar application had a lower effect on tree growth compared to wood ash and lime. This study highlights the potential of using wood ash to improve poplar growth on sites with low soil pH and that application methods can be adapted for different site conditions, thereby supporting the early establishment of these fast-growing plantations in sites with suboptimal soil conditions.