On Earth, human life is enabled by plants which provide us with calories, vitamins, fuel, medicines, and oxygen to breathe. In addition, recent scientific studies indicate that plant cultivation reduces anxiety and depression and has a positive influence on diabetes, heart disease, obesity, and longevity. Perhaps this is the reason that 80% of the cultivated plant species on planet Earth are not used for any food related purpose. On long duration space missions astronauts live in close quarters isolated from the natural world where the basic activities like eating, sleeping, and attending to bodily functions are difficult and stress producing. Recent research conducted on the International Space Station suggests that space gardening helps astronauts to cope with the sterile space craft interior, allows them to combat boredom, as well as some of the other negative psychological effects of their long period of confinement. Specific examples of International Space Station gardens include astronaut Scott Kelly's first zinnia to bloom in space and astronaut Peggy Whitson's small crop of space soybeans. For many thousands of years people making long journeys have taken plants for food and recreation with them. It is likely that when humans travel to Mars they will continue this practice. The plants that Mars explorers take with them will provide a source of fresh fruits and vegetables , fresh air to breathe, and perhaps a psychological benefit that is crucial to the success of their mission.