From cathedrals to dreaming sites, every culture needs its monuments. But the landscape and built culture of southern New Guinea conspire to erase physical memory. In the ever-changing environment of mud, plants, and water, there are no rock formations to serve as durable traces of the past. Wooden houses decay within a decade or two. Garden clearings grow back after a few years. The savannah edge, if not maintained by regular bushfires, is soon recolonized by forest. Against this mutable environment, stability of external memory is given by the coconut trees planted anywhere a plant can grow: beaches, swiddens, old villages, house yards. Almost every coconut palm serves as a tab (sign)—a reminder of stories of garden clearings, resettlements, disputes, pledges, or intentions. For most, there are individuals with the special knowledge needed to tell their stories. These trees form an arboreal history anchored in their durability and in the clear symbolic and practical intentions that accompany each planting. In this paper, I illustrate the trees' mnemonic value, drawing on hundreds of interviews conducted by local interviewers in their own languages—Nen, Nmbo, and Idi. Responding to the flexible interactions between each interviewer and interviewee, they cover many topics, from memories of old gardens, abandoned houses, or temporary periods in other villages, through reconciliations, to girl-abducting teenagers and midlife contraceptives. In presenting this corpus of material, I marry linguistic and anthropological analyses to show how a network of communities, linked by marriage and exchange across language boundaries, uses these living monuments to maintain its histories across a broad range of spokespeople.