What size greenhouse is best for your needs? 

The facts are that far to many people either choose one that is much to large or one just to small for their needs.

The best choice is between 144 & 288 sq. ft.. Units 10'x14' through 12'x24' range. They are large enough to meet most hobby gardner and small start up nursery needs and small enough to be cost effective and much easier to maintain on a long term basis. Even if your furture needs dictate more and larger greenhouses, you will have honed your greenhouse skills while managing the smaller one. Remember that regardless of how many or the size of greenhouses added later you will always be able to utilize the smaller one. If for nothing else it will make a great seedling starter house or used to house your prized specimen plants.