Virginia’s food system directly impacts the survival and viability of farms and farmland; the economic development of rural and urban communities; the care, restoration, and resilience of ecological resources such as local waterways; and critical health issues. We use the language of community, local, and regional food systems to broadly define a complex and interconnected set of systems and pathways that comprise sustainable food production, processing, distribution, consumption, and waste management to bring about social, economic, and ecological change that benefits all residents.

According to the United States Department of Agriculture 2012 Census of Agriculture, sales from greenhouse-grown food crops equaled around $800 million in the U.S. Crops grown included tomatoes, lettuce, cucumbers, peppers, and berries, with hydroponic production operations making up about 64% of the total production (cwt) (USDA Census of Agriculture, 2012). Demand for greenhouse-grown produce continues to increase, providing growers with unique opportunities to tap into this expanding market. Although greenhouse systems provide a more protected environment than field-grown systems, it is important to understand the unique food safety risks and possible sources of contamination when growing produce in these systems. Identifying food safety hazards are necessary to implementing practices that reduce the risk of contamination during the pre-plant, production, harvest, and post-harvest handling stages. Use the checklist below to guide you in asking important questions targeting possible risks at each of the greenhouse system stages.

Plant growth regulators (PGRs) are chemicals that are designed to affect plant growth and/or development (figure 1). They are applied for specific purposes to elicit specific plant responses. Although there is much scientific information on using PGRs in the greenhouse, it is not an exact science. Achieving the best results with PGRs is a combination of art and science — science tempered with a lot of trial and error and a good understanding of plant growth and development. good understanding of plant growth and development.

According to the 2017 Census of Agriculture, U.S. greenhouse vegetable farms more than doubled from 2012 (USDA 2019). Virginia fell within the top 10 states for acreage of vegetables and berry crops grown under protected culture. Protected culture includes greenhouses and structures like high tunnels. With close to two and a half million square feet devoted mostly to tomatoes, vegetables, herbs, and strawberries, the value of Virginia greenhouse sales in 2017 was over 31 million dollars! A lot of this increase in square footage was due to the addition of large operations coming into Virginia.

With the increasing number of controlled environment agriculture farms, Virginia Cooperative Extension is working closely with specialty crop growers to address the challenges of establishing and managing hydroponic greenhouse operations. Growers interested in producing food crops in controlled environments can use several different types of hydroponic systems. One of the most common types of hydroponic systems is called nutrient film technique (NFT).

One common type of hydroponic system is known as a media system and utilizes some type of containerized media to grow plants. This media or substrate is used primarily to anchor the plants while nutrient solution is delivered to the plants via sub-irrigation or top-irrigation. The terms media and substrate will be used interchangeably in this publication.

This factsheet is part of a series of seven factsheets targeting beginning farmers growing edible crops using hydroponic greenhouse systems. There are also five videos that are related to the factsheets and included in the numbering sequence.