Reducing peat consumption in hobby gardening offers considerable potential for reducing CO2 emissions, since peatlands are one of the most important natural carbon sinks. While existing research focuses on the products and their diffusion, we focus on people and their practices of gardening. So we conducted 44 interviews with hobby gardeners in Germany from three different contexts: gardening at home, in an allotment garden, and in an urban gardening initiative. Our findings show that substrates are not a major part of gardeners' social interactions. Purchasing substrates is a utility-driven process with, compared to gardening itself, mostly passive information behavior. Although (basic) knowledge about peat is widespread among hobby gardeners, price is the dominant purchase criterion for substrates; sustainability does not play an important role. Our results suggest that communication campaigns by governments and companies should convey substrate-related messages in those places where gardeners go to seek information, e.g. gardening-related publications. Communication should focus on the functional value of peat-free substrates and not just explain environmental benefits. Lastly, campaigns should target home gardeners rather than urban gardeners and allotment gardeners who rarely buy any substrates but rely on their own production.