Urban landscape planners and policymakers aim to find robust/optimal green infrastructure (GI) placement solutions that can perform well over a wide range of plausible futures and meet different objectives. While some studies on the spatial allocation of GI embraced multi-objective optimization to inform multi-functional GI placement decisions, many GI optimization studies are silent on potentially important questions raised by the deep uncertainties surrounding GI models, decision levers, and success metrics. This review paper provides an overview of this research gap, potentially relevant uncertainties for GI placement, and suggested research directions.