Plants and specifically indoor pot plants have featured as a prominent object in human-computer interaction (HCI) studies for more than two decades. Motivated by recent discourse in posthumanist and entanglement HCI, this paper seeks to contribute to the more-than-human turn in interaction design. It uses a twofold approach. We first engage in theoretically grounded inductive reasoning to postulate that the role and agency of plants in interaction design projects ought to change. This is backed up with a deductive approach based on a critical meta-analysis using a methodical review of human-plant interaction studies. The analysis identified a range of characteristics that we discuss in relation to study motives and outcomes. Our findings suggest that so far, plants-as-objects in interaction design are used as (i) a proxy for nature; (ii) a trigger for human experiences or; (iii) an interface for other actions. Our synthesis combining theory and meta-analysis contributes to ongoing design discourse on the ethical and societal implications of using plants in technologically mediated environments. We offer reflective remarks on how HCI can re-conceptualise plants from utilitarian objects towards recognising their value as living co-inhabitants.