A lot of people think that once they purchase a greenhouse they are done.
They think that it will function completely on its own.
This could not be further from the truth.
It is important to buy a greenhouse structure that will fit your needs.
But, it is equally as important to purchase and install the proper accessories.
I will list the items considered to be necessary and also some items which would be considered optional.

1. A heater - If you intend to keep your greenhouse above the temperature outside this is a total necessity.
   The greenhouse itself will not maintain any of the heat it has built up during the day unless you are using solar type practices.
   Greenhouse heaters are electric, natural gas or propane.
   
2. Ventilation systems - These will consist of a motorized fan, motorized intake shutter and a thermostat.
   The fan and intake will be wired to the thermostat so that they will come on at the same time and give a good flow of air all the way through the greenhouse.
   I consider this to be a necessity.
   
3. Roof vents - Most greenhouses will come with roof vents.
   They are an excellent way to vent hot air out through the roof of the greenhouse.
   These may be manual or automatic.
   The vents are a necessity.
   Automatic openers are an option.
   
4. Shade cloths- A shade cloth is an inexpensive way of controlling the heat inside a greenhouse.
   They are typically installed only on the roof, but some people will also use them on their sidewalls.
   They can be installed outside the roof or on the inside of the roof.
   They are available in many different percentages.
   This is definitely optional and may be added at any time.
   
5. Benches - Most people will use benches in their greenhouses.
   There are a lot of different styles including aluminum and fiberglass benches.
   You probably will not want to use a wood bench unless it is cedar due to the high humidity of the greenhouse.
   Again, an option.
   
6. Propagation mats or heat mats - These are a really important accessory if you are starting seeds, protecting seedlings, or simply trying to cut down on the heat needed for your greenhouse.
   They will warm the soil and increase germination rate.
   This is an option, but is a really valuable tool.
   
7. Watering system - An automatic watering system is a favorite among busy greenhouse growers.
   This way you can assure that your prize plants or seedlings will receive the proper amount of water.
   You can set these on timers to water once, twice a day, or whatever schedule your plants will need.
   Most people will find this an option, but I consider it a necessity.
   

Don't fall into the trap of thinking buying a greenhouse is the only thing you will need for healthy, happy plants.
Make sure you accessorize it correctly in the beginning and you will be much happier - as well as your plants.