Absolutely not! You can have a simple vegetable garden of a few pots, or a large plot of rows and rows of vegetables. Make sure to choose vegetables native to your area, and plant them in their ideal condition (sun, partial sun, etc.). You will only need a greenhouse if you are trying to grow exotic vegetables not native to your geographical area.
Growing vegetables in greenhouses needs an earlier harvest, and vegetables that do well in an outside garden. Before building a greenhouse, decide on a location that is accessible and has sunlight for at least part of the day.Electricity should be proper for run heaters, water systems and lighting.Maintain greenhouse temperature of 28 degrees.