Plants perform in a specific Eh–pH spectrum and they rely on various processes to ensure their homeostasis, which plays a central role in their defense. The effects of multiple stresses, all translated into oxidative stress into the plant, and the capacity of the latter to respond to these stresses results in specific Eh–pH states in plants. We reviewed plant-invertebrate pests and plant-pathogens interactions under a Eh–pH homeostasis perspective by extensively analyzing the literature, which converges and supports a set of hypotheses. We report examples showing how the development and attacks of pests are correlated to spatio-temporal variations of Eh–pH in plants. We provide evidence-based discussion on how Eh–pH homeostasis can open a new perspective on plant health, and help unravel and disentangle the many Genotype x Environment x Management x Pest and Pathogen interactions. We propose an original perspective on energy allocation and growth-defense tradeoff by plants based on the Eh–pH homeostasis model. Finally, we show how Eh–pH conditions in the rhizosphere are the results of multiple interactions between the root system and microorganisms. Based on this, we hypothesize that soil suppressiveness is derived from soil structure leading to diverse Eh–pH niches that harbor a diversity of microorganisms. The Eh–pH homeostasis model proposed herein is central to soil and plant health. An Eh–pH perspective could become a very powerful tool to develop a “one health approach” unifying a large range of bio-physical processes in a very coherent and consistent manner.