Membraneless compartments assembled by liquid–liquid phase separation have moved rapidly from a curiosity of in vitro biophysics to a working explanation for how crop plants sense temperature, water, ions and pathogens. In this review, we synthesize the physicochemical rules that govern condensate assembly in plant cells, trace how those rules are deployed across the horticultural pathosystems and stress physiologies that matter for food production and evaluate the emerging engineering and chemical toolkits — synthetic scaffolds, optogenetic phase regulators, condensate-targeting phytovirucides and condensate-aware breeding alleles — that aim to convert condensate biology into agronomic gain.