Plants will play a crucial role in space exploration because they provide a source of fresh food for astronauts, revitalize habitat air, and help recycle resources. However, to use plants effectively for space exploration, it is important to understand how they grow under the harsh environments of space. Many microbes that are intimately associated with plants are known to improve the plant’s ability to tolerate environmental stresses on Earth. These beneficial microbes could also confer similar advantages to plants in space; however, we do not know how exposure to the space environment alters these associations.