Will greenhouse-grown vegetables replace ornamentals in U.S. greenhouses? – Part 1

Pathogens, spray regulations and labor issues should be considered before growing vegetables in a greenhouse.

Kalamazoo, Mich., was once known as the celery capital of the world. Today, greenhouses growing ornamental crops are a common sight throughout that city. But could a shift be underway to transform Kalamazoo and many other cities back to their vegetable-growing roots? Some ornamental greenhouse growers throughout the United States have been re-entering the vegetable production business to fill empty greenhouses during non-peak production times for ornamentals. Greenhouse-grown produce might be able to capture higher prices at the market compared to their field-grown equivalent, depending on availability of product from other local producers and producers in other areas of the country. Michigan State University Extension recommends that producers consider many factors before converting ornamental production space to vegetable production.

Tomato production
Tomato production in the Netherlands. Photo credit: Kristin Getter, MSU

While common diseases may be the same between vegetables and ornamentals including Botrytis, Pythium and Rhizoctonia, products labeled for their management often differ for edible crops. For example, Subdue MAXX, which provides control of Pythium and Phytophthora for ornamentals, turf, and non-bearing fruits and nuts, contains the same active ingredient (mefenoxam) as Ridomil Gold, which is labeled for numerous fruits and vegetables. While containing the same active ingredient, sprays applied to edible crops may have different re-entry intervals and have instructions about spray and harvest timing. Furthermore, some sprays labeled for field-grown vegetables can be used in the greenhouse, unless the label specifically states that spraying in a controlled environment is prohibited. Generally, there has been a shift in regulation over the last couple of years that chemicals are being labeled to be crop-specific instead of whether they are being sprayed on plants grown in a greenhouse or out in the field. It is critical to always follow the label instructions.

In addition, edible crops should be separated from ornamental crops to not only prevent accidental applications of non-labeled chemicals to your vegetables, but to prevent disease spread between them. For example, thrips feeding on tomato plants may carry tomato spotted wilt virus to vulnerable ornamental crops in an adjacent house. For more information on diseases between ornamental and vegetable crops, see the Greenhouse Product News article “Crossing Over: Vegetable Diseases in the Ornamental Greenhouse.” A 2013 guide for insect, disease and nematode control for commercial vegetables can be bought at the MSU Extension Bookstore.

When considering a new vegetable crop, be sure to also calculate the increased labor expenses associated with finding and hiring employees to harvest the crop. Especially in today’s climate, healthcare is a hot-button issue with agricultural businesses. If a business is close but still under the threshold of 50 fulltime-equivalent employees, the hours worked by seasonal employees may push businesses to offer healthcare meeting the criteria of the Affordable Care Act to all fulltime employees. Therefore, labor-intensive crops may have wider implications on other aspects of the business.

In Part 2 of this series, MSU Extension will discuss production expenses and challenges and food safety regulation with growing vegetables in a greenhouse. We will also state advantages of entering the greenhouse vegetable market.

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