High tunnels found effective for finishing cold-tolerant annuals

December 8, 2014, American Society for Horticultural Science
In experiments comparing high tunnels with greenhouses for growing bedding plants, petunias finished in an unheated high tunnel (left) were shorter and more compact than those grown in a heated greenhouse (right). Credit: Photo courtesy of Neil Mattson.

Energy costs account for one of the largest expenses in commercial greenhouse production of annual bedding plants. Naturally, bedding plant producers are searching for more energy-efficient production methods that can reduce fuel usage and increase profits. Christopher Currey, Roberto Lopez, and Neil Mattson published a study in HortTechnology that gives growers in northern latitudes valuable information on finishing practices for annual bedding plants. The researchers compared traditional heated greenhouses with unheated high tunnels for growing 10 popular bedding plants at two USDA Hardiness Zone 5 locations: Ithaca, New York, and Lafayette, Indiana.

According to the researchers, energy for heating commercial greenhouses in northern climates can account for 10-30% of total operating costs. "In floriculture, are traditionally used in cut flower production for season extension and frost protection," the authors said. "Though not designed to be equivalent to greenhouses for year-round protected crop cultivation, high tunnels have the potential to be used for seasonal crop cultivation." Daytime air temperatures inside high tunnels can range from 5-20 °C warmer than ambient outdoor air temperatures, but temperatures at night in unheated high tunnels can be about the same or occasionally lower than outdoor air temperatures.

The scientists grew 10 popular (angelonia, vinca, celosia, dianthus, geranium, petunia, french marigold, viola, snapdragon, and osteospermum) in both an unheated high tunnel and a glass-glazed greenhouse with an 18 °C temperature set point at both Cornell University and Purdue University.

At Cornell, all 10 species survived in the unheated high tunnel environment when moved on April 1. The lowest recorded temperature at the Cornell high tunnel was -3.2 °C. "It is interesting to note that the cold-sensitive species angelonia, celosia, and vinca survived this short-term cold exposure," said corresponding author Roberto Lopez. However, most of the species showed a significant delay in flowering when grown in the high tunnel compared to when they were grown in the heated greenhouse. Although seven of the species exhibited a delay in flowering in the high tunnel compared with those in the heated greenhouse, there were no differences in days to flower for geranium, osteospermum, and viola grown at Cornell, and viola grown at Purdue.

At Purdue, several species were lost because of a cold temperature event (-6 °C), necessitating a second planting (April 8). "Delaying the high tunnel transplant date was an effective method for reducing plant mortality and reducing delays in days to flower because of the cold temperature environment of the high tunnel," the authors said. For the second planting, osteospermum was the only species that flowered significantly later in the high tunnel, a delay of 7 days compared to the greenhouse-grown plants.

According to author Neil Mattson, besides savings in energy costs, finishing cold-tolerant bedding plants in unheated high tunnels may enable growers to meet their seasonal peak space demand in a cheaper-to-build high tunnel while still providing some protection compared to the outside environment. "Further, in the current study finishing bedding plants in high tunnels led to improvements in measures of plant quality for some crops, such as shorter, more compact plants than greenhouse-grown counterparts. This could reduce the need for application of chemical plant growth regulators."

The authors concluded that production of cold-tolerant annuals in unheated or minimally heated high tunnels can be a "viable alternative" for commercial producers aiming to reduce energy costs. "While we acknowledge the risk of finishing spring bedding plant crops in an unheated environment, there is a potential for gains in profitability for producers because of the lower capital and of high tunnels as compared with conventional greenhouses," the authors said.

Explore further: Ornamental plant seedlings grown with LED lights at Purdue

More information: horttech.ashspublications.org/ … nt/24/5/527.abstract

Related Stories

Ornamental plant seedlings grown with LED lights at Purdue

October 29, 2014

Purdue University researchers' success in using red and blue LEDs as the only source of light to grow ornamental plant seedlings indoors has led to a new phase of determining whether they can reduce production time with more ...

LEDs shine in bedding plant production study

July 21, 2014

Growers of annual bedding plant seedlings or plugs work to produce compact, fully rooted transplants with a large stem diameter and high root dry mass—qualities that make seedlings less susceptible to damage during shipping ...

High tunnels to simulate climate change

May 30, 2014

(Phys.org) —Okra, peanuts, cotton and bananas are not exactly staple crops on Ithaca farms and home gardens. But as the world gets warmer, will there be a place for tropical varieties in New York state? And what will happen ...

Recommended for you

Researchers engineer a tougher fiber

February 22, 2019

North Carolina State University researchers have developed a fiber that combines the elasticity of rubber with the strength of a metal, resulting in a tougher material that could be incorporated into soft robotics, packaging ...

A quantum magnet with a topological twist

February 22, 2019

Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.