Season extension

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Growers producing food for the local market use a variety of methods to extend the growing season beyond what is traditionally possible in the local climate.

Season extension methods can be as low-tech as starting transplants indoors and laying inexpensive row cover cloth over small metal hoops to create “low tunnels.”

High tunnels or hoop houses are mid-range options. As opposed to greenhouses, high tunnels are usually made of less expensive materials with flexible plastic coverings, in-ground or raised beds (as opposed to bench-top production), and passive heating and cooling such as row covers and roll-up sides. Some local zoning boards consider high tunnels as temporary structures (check your local rules first!). The relatively low construction and maintenance costs and the potential (with significant work!) to move a high tunnel to a new site if necessary have made high tunnels popular with urban farmers. Penn State Extension has particularly good resources on high tunnel construction and management. And the USDA-NRCS has offered incentive grants to help farmers build high tunnels to extend the growing season.

Greenhouses with permanent plastic or glass walls, supplemental lighting, and heating systems, are much more expensive and are mostly used at a small scale for transplant production and at a large scale by plant nurseries to produce potted plants for sale to public customers or to landscapers and garden centers.

Indoor production could also be considered a form of season extension. There are also hybrids of the various methods, with some aquaponic urban farmers setting up their systems in high tunnels and ground-based urban farmers using double-envelope systems of low-tunnels within high tunnels to maximize the temperature differential between what the crop experiences and the outside temperature.

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