Plants in space

The growth of plants in outer space has elicited much scientific interest moving from fictional discussion such as the trees on the brick moon space station in the 1869 short story "The Brick Moon". In the late 20th and early 21st century, plants were often taken into space in low Earth orbit to be grown in a weightless but pressurized controlled environment, sometimes called space gardens. In the context of human spaceflight, they can be consumed as food and provide a refreshing atmosphere. Plants can metabolize carbon dioxide in the air to produce valuable oxygen, and can help control cabin humidity. Growing plants in space may provide a psychological benefit to human spaceflight crews. Usually the plants were part of studies or technical development to further develop space gardens or conduct science experiments. To date plants taken into space have had mostly scientific interest, with only limited contributions to the functionality of the spacecraft. The 1971 Apollo Moon tree project was a more or less forestry inspired mission and the trees were part of the USA's bicentennial celebration in 1976.

The first challenge in growing plants in space is the absence of gravity, which is important for root development, soil integration, and watering. Other problems include providing appropriate lighting. For longer-term growth, inorganic nutrient supply to the roots as well as biogeochemical cycles, and the microbiological interactions in soil-based substrates are particularly complex. However, modelling and experimentation have indicated that space farming should be possible in hypo- and micro-gravity.

NASA has tested growing plants in space to help feed astronauts and to provide psychological benefits for long-term space flight. In 2017, Chinese cabbage (Brassica rapa) grown in the International Space Station was eaten by the crew, as well as saving some for study after return to Earth.