|Adapted from Fact Sheet 593, University of Maryland Cooperative Extension Service
Selecting a Site
Location of a greenhouse is critical to future profitability. Before deciding on the location, layout and orientation of the greenhouse, a grower should have defined how and where crops will be marketed.
A retail operation should be located on a well-traveled road, near major highways or within 20 minutes of consumers since proximity to customers increases customer traffic. In addition, retail operators are required to have sales tax collection permits. Local extension agents can direct growers to the appropriate departments to obtain permits and licenses.
A wholesale greenhouse should be located where zoning restrictions will not limit expansion of the operation. Check with local county governments to determine restrictions that apply to a greenhouse operation. These include specific licenses or permits required to operate a greenhouse. For example, only certified users may apply restricted-use pesticides.Land cost and zoning restrictions in and around most cities often preclude the establishment of wholesale operations.
Having chosen an appropriate market, customer base and location, the grower should consider the following factors when evaluating a potential site: greenhouse orientation, topography and natural windbreaks, roadways, water supply and quality, proximity to labor force.
Water supply and quality. Each year you will need up to 6 acre-feet of water for every acre of greenhouse. The water can come from such sources as wells, ponds or city utilities. Some growers use low-yielding wells by pumping water into holding tanks or ponds, and then pumping from these large reservoirs at high-demand times.
Not all water is suitable for irrigation purposes. Before using any water, have it tested by a commercial water testing lab which has experience with greenhouse water requirements. State and local health department water tests will not alert you to excessive sodium, iron or pH problems that should be corrected before using the water for plant irrigation. Finally, pond water should be chlorinated at the time of use to kill algae and root rot organisms.
Labor force. The greenhouse business is labor intensive and obtaining experienced labor can prove troublesome. A readily available labor force and support services should be within 20 minutes of a greenhouse site. When determining area labor supply, investigate the competition for both skilled and unskilled seasonal help. Most greenhouses have peak labor requirements from February to June. In order to attract skilled employees, some greenhouse managers allow workers to create their schedules and expand the employee pool to include retired and disabled people.
Labor-reducing equipment, such as automated irrigation equipment, computer-controlled heating and cooling systems, automated seeders and potting machines, can reduce labor requirements. Although the initial capital outlay is considerable, these devices enable growers to increase productivity with fewer but better trained permanent employees.
Greenhouse orientation. A greenhouse site must be free from both winter and summer (deciduous tree) shadows. Adequate space for expansion of greenhouses and support areas also should be available. An east-west greenhouse will transmit about 25 percent more light than one situated north-south. On the other hand greenhouses that are connected together should be constructed north to south to provide even light coverage within the houses throughout the day.
Roadways. Greenhouses must be accessed by adequate roadways and bridges. They are essential for delivery of supplies and pickup of finished plants. Retail operations should separate customer and service entrances and provide adequate parking. However, locating the greenhouse near parking areas with high lighting will limit the types of crops you can grow.
Topography. The natural topography of a greenhouse site is important. Greenhouse structures should be located on slopes of less than 5 percent. This will facilitate moving carts of plants around the complex. Avoid locating greenhouse operations in a flood plain, frost pocket or on a hilltop where heating bills will be high.
Windbreaks. Nearby buildings or coniferous trees and hedges to the west and north of your greenhouse site act as windbreakers to slow winter wind before it hits the greenhouse and can greatly reduce heat loss in winter. However, any windbreak should be far enough away from your greenhouse to prevent shading.