H.’s superlative new study brings together a vast range of material examining sacred trees from across the Roman world. As the title suggests, however, H.’s aims are far more ambitious than a straightforward compilation of interesting case studies. In addition to providing fresh interpretations of sacred trees in many different literary and visual contexts, the book also works to show how ancient discussions of trees can shine new light on the ways in which Romans perceived, approached and interacted with the divine, prompting challenges to a number of important and commonly-held views prevalent in the study of Roman religion. In defining what is meant by a sacred tree, for example, H. seeks to move beyond the rigid definitions of sacred, typically involving formal public dedication, which has dominated the subject for so long. Instead, H. advocates a more flexible position which acknowledges the myriad ways in which a tree ‘intersects with Roman religious thought and practice’ (p. 3). This opening stance sets the tone for much of what follows.

The first two chapters are concerned primarily with situating the book within its broader scholarly context. This is not an easy task, and H. provides an extensive and thorough outline of the prominent place that trees occupied in early works of Roman history, as well as ethnography and comparative religion. Trees have had a long and complicated history within the study of Roman religion and, as these chapters demonstrate, even though modern scholars pride themselves on having moved on from the theories which dominated previous generations, the study of trees has struggled to break free from old assumptions about their meaning and materiality. In particular, H. attacks what she sees as the Protestant-centric stranglehold on the subject (this axe is well and truly ground by the end of the book), which, it is argued, has clouded views concerning sacred trees by consistently relegating them, and the rituals connected to them, to the realm of the ‘primitive’.

After guiding the reader through the many pitfalls and problems that have plagued the subject in the past, Chapter 3 moves on to the subject of ‘arboreal matter’, arguing that the status of trees as living things had consequences for Roman perceptions of their sacrality. Their potential vulnerability also meant that there were important questions to be asked when performing acts of arboriculture, as well as what it meant and what to do when a sacred tree was damaged, appeared to be in decline or died. If a sacred tree had to be replaced, was the replacement any less sacred than its predecessor? The meat of the chapter concerns the thorny problem of the ficus Ruminalis and entails a close reading of conflicting reports surrounding it. The exact words of writers like Pliny the Elder are painstakingly dissected as H. demonstrates how location, memory, association, overlapping traditions and even general proximity to other sacred spaces and objects may all combine to contribute towards ideas about this fig's sacrality.

Chapter 4 continues to question the nature of sacrality and, by focusing on arboriculture, raises the issue of when to think in terms of sacrilege and violation. Once again, H. is fighting an uphill struggle against enduring assumptions about the general ‘inviolability’ of trees, predicated on the supposition that sacred trees are the property of a god and bolstered by some oft-cited poetic examples depicting the damaging or harming of trees. These initial questions set the scene for a larger section on the rituals carried out by the Arval brothers within the grove of Dea Dia. This requires a close analysis of the specific words and phrases recorded in the numerous inscriptions, in the course of which H. considers the motivations behind the Arval brothers' sacrifices and work within the grove at key points within the year. This opens up a discussion of the double-edged term piaculum and the extent to which piacula were performed by way of atonement. H. argues against the standard interpretations, instead emphasising that the act of physically engaging with the trees within the grove was, itself, an act of religious significance and that by choosing to interact with these trees in the way and at the time that they did, the Arval brothers ‘expressed just how much their relationship with these trees mattered to them’ (p. 152). The chapter goes on to consider those inscriptions dealing with trees ‘in crisis’ and the nature of the sacrifices performed in response to them.

Chapter 5 deals with the agency of trees themselves and the ways in which ancient authors attempted to grapple with questions of ‘natural’ behaviour and the extent to which divine interference might be at work even in cases that could be attributed to natural causes. This involves an analysis of the important but problematic term numen, which played a central role in early studies of Roman religion and was especially relevant to the study of sacred trees. H. argues forcefully for accepting, rather than resisting, the apparent flexibility of the term and suggests that was precisely what made it useful for Roman thinkers. The chapter also deals with arboreal portents and the problems Romans faced in identifying what was or was not meaningful about a tree's behaviour and how signs were to be interpreted if they were recognised. The famous palm tree which grew from an altar at Tarraco dedicated to Augustus demonstrates how conflicting interpretations might exist and evolve side by side and could have significant implications for broader issues, including the divinity of the emperor.

Chapter 6 moves beyond the more headline-grabbing arboreal portents to consider other ways in which trees intersected with the divine and how this could be used to flesh out the identities of deities. The links between trees and particular deities worked in multiple ways beyond the level of consecration. The role of arboreal epithets and their implications are also considered, with much of the literary and epigraphic evidence coming from Greek sources. The latter half of the chapter addresses some prominent examples of trees in visual culture, again considering how their presence can convey something more about the identity of gods and cult spaces and prompting the question of whether any tree situated in a cult space was imbued with significance automatically. The final chapter offers an extremely succinct conclusion, and is followed by an appendix collecting together the inscriptions from the Arval grove.

This is an extremely well-researched and nuanced study of a difficult and important subject. The questions raised by H.’s study have the potential to reach well beyond her chosen area of focus and, as such, this book is to be recommended to all scholars working on the subject of Roman religion.