Different plants like to have different types of heat, light and moisture; this is what makes the areas of your garden and your landscaping different. In your greenhouse you are also going to have to find different environments or make different environments for the different varieties of plants that you choose to grow. The different smaller climates or environments in your greenhouse are also called microclimates because these are just smaller climates in one large environment.
If you are planning on growing different vegetables, bushes, shrubs, flowers and green plants in your greenhouse you will notice that all of these types of plants need different amounts of light and heat in order to grow and thrive fully. Some of the considerations that you must think about when placing your plants or choosing your plants in the correct microclimates are: Where is the brightest and longest lasting sun portion of the greenhouse? Where is the shadiest portion of your greenhouse (under shelving or larger plants)? Keep in mind that it will be hotter towards the top of your greenhouse and the lower shelving and the flooring of your greenhouse will be cooler. The closer that you keep a plant to your sidewalls or to your roof the more sun rays (intense light) that they are going to get. If you are using heat in your greenhouse, keeping a plant near to the heat source will be the warmest in the winter months. Plants near vents and fans should be more hardy plants that can withstand the breeze.
If you are going to be using microclimates in your greenhouse one of the best ways to do this is by making a drawing of your greenhouse, writing in the parts of the greenhouse that you know are the brightest, hottest, shadiest etc until you have broken down all the areas of the greenhouse for best placements of your plants. Some examples of what your particular plants might be are these: Lettuce will grow in a shady to bright light but needs only a cooler to warm temperature in order to grow properly so keep your lettuce away from your heat source, away from the walls and away from the temperatures that rise at the roof. But if you want to grow beans in your greenhouse, they need a bright light to an intense bright light with a warm to hot temperature to grow properly. You should keep your beans near the heat source, near the roof or the sidewalls where the sun rays are the brightest and away from vents and fans where the breeze could cool them too much for them to grow. Planning your greenhouse climates and plants is similar to the planning of your landscape where you place certain plants in the light, in the shade and where the soil matches their needs.