It's reccommended that each member of your family be allocated between 15-20 plants per year to fully provide them with enough nutrition. This number changes depending on what you're growing, and how often you plan on using the crop afterwards. Any extra produce can be sold, turned into something new, or saved for later via canning, drying, or freezing.
The average family in America would require about 800 sq feet of garden space to grow enough vegetables to thoroughly supply their diet throughout a year. This provides room for saving and preserving extras, as an outdoor garden will be restricted by cold temperatures in the winter. This is larger than the space required for greenhouses, as greenhouse's maximize growing conditions, and result in high, productive yields.
