Irrigation controls rely on whether you use a drip or misting system. That is a choice you’ll need to make in relation to the types of plants you want to grow. For temperature you’ll need a greenhouse thermostat which works in the same way as an in-house thermostat.

For humidity you’ll need a product that keeps the air between 20 and 80 degrees Fahrenheit. For plants with special needs you can find products that will keep the humidity between a narrower range.

Though you start out small, you may, eventually, want to expand your greenhouse. To keep from rebuilding your greenhouse every time your gardening becomes more ambitious start out with an expandable greenhouse. A greenhouse made of PVC piping will easily refit for this purpose.

The least expensive greenhouse kits are definitely the portables. Portable greenhouses can start under $100, and are great for the beginning grower who doesn't want to do things year-round.