Forests are crucial for climate change mitigation as they absorb and store large amounts of carbon dioxide. In Finland, ash fertilization of drained peatland forests has been identified as part of the climate change mitigation strategy, yet it is implemented notably less than it could be. Therefore, this study aimed to identify most effective nudges, nudge+ and boosts that could steer Finnish non-industrial private forest (NIPF) owners to adopt ash fertilization in their forest. Semi-structured interviews with 19 NIPF owners were analyzed using the Behaviour change wheel to identify key factors influencing owners’ willingness to engage in ash fertilization. Most factors raised by forest owners were related to reflective motivation encompassing both drivers and barriers to practicing ash fertilization. We also identified possible cognitive biases that were influencing decisions. The suggested nudges, nudge+ and boosts address both the specific concerns of the forest owners and the underlying heuristics. For example, framing ash fertilization as a standard procedure of professional forest management and including it into forest management plans could facilitate overcoming status quo bias that may hinder the adoption of novel forest management practices. These findings are directly applicable for creating nudges, nudge+ and boosts on ash fertilization for experienced, professionally managing NIPF owners with larger forest estates. Our study also offers an approach that can be adapted for broader application in environmental and climate-friendly decision-making, contributing to the growing body of literature on the intersection of behavioral science and environmental management.