Plants must tolerate and grow under a wide variety of environmental conditions. It is clear that the phytomicrobiome supports plant growth under normal and stressful growing conditions and these functions are carefully regulated. The phytomicrobiome can promote plant growth under normal growing conditions by providing improved access to nutrients and production of phytohormones. Microbes can improve growth under stressful growing conditions by inducing abiotic stress tolerance via production of antioxidant enzymes, altering plant metabolism, affecting the rate of photosynthesis and shifting osmolyte concentration in plant tissues. The phytomicrobiome also helps plants resist biotic stress by competing against other microbes for niche space and nutrients, producing of antibiotic compounds, and inducing systemic resistance by producing microbe-to-plant signal molecules. However, our understanding of these mechanisms is still relatively new and the importance of root exudates, and intermicrobial signaling, along with currently unidentified mechanisms should be the focus of future research.