Greenhouse Canada

Features Lighting Structures & Equipment

January 29, 2008  By Geoff Koch

A popular resource book shows how manipulating light levels can help growers produce consistent quality plant material through the year.

24Michigan State University horticulture researcher Erik Runkle thinks that no one should be kept in the dark about greenhouse lighting – especially with the book Lighting Up Profits: Understanding Greenhouse Lighting available.  “In general, many growers don’t really understand the concepts of lighting, so they don’t use lighting systems to improve their crop production,” said Runkle, who co-edited Lighting Up Profits with Paul Fisher at the University of New Hampshire.


Improved management of light can enable a grower to add an extra cycle of plants to a production schedule, speed up the flowering of perennials to take advantage of higher out-of-season prices, or make more informed decisions when buying new lighting equipment.

Runkle, whose work is supported by the Michigan Agricultural Experiment Station, hopes to equip readers with a soup-to-nuts understanding of greenhouse lighting. His book includes grower case studies, conversion and summary tables, and dozens of colour photographs. 

The book even includes a concise description of light itself. “This may seem elementary, but it’s an important first step, given the different units of measurement, such as lumens per square metre (lux), foot-candles and micromoles, that are used by growers,” said Runkle, who’s also an MSU extension specialist. “In effect, growers often speak different languages when it comes to light.”    

Undergraduate horticulture students would also benefit. The book’s study questions and accompanying CD with conversion software and PowerPoint slides can be used as teaching materials. Runkle hopes to teach a one-credit lighting class at MSU that will draw heavily from information in the book.

Michigan ranks third in the U.S. behind California and Florida in floriculture products, with annual wholesale sales of ornamental and flowering plants of $342 million, according to the Michigan Department of Agriculture.

Given Michigan’s weather pattern – Lansing's 191 cloudy days per year are just 10 fewer than Seattle’s – these sales depend heavily on the ability of growers to make the most of their lighting resources.

“In Michigan, as cloudy as it is, it's important to be able to manipulate light levels to produce consistent quality plant material through the year,” said Allen Pyle, a researcher and marketing specialist with C. Raker & Sons, a floriculture wholesaler in Litchfield, Mich.    

The 15 chapters of Lighting Up Profits cover manipulating light levels and almost everything else related to light in greenhouses.

A portion of the book’s royalties will be given to the Floriculture Industry Research and Scholarship Trust (FIRST), an East Lansing-based non-profit organization that funds research and education projects for horticulture students and educators.       

In his research, Runkle studies how changes in light duration, intensity and quality affect plant growth and development in a range of garden species. Working with Project GREEEN (Generating Research and Extension to meet Environmental and Economic Needs), the state’s plant agriculture initiative at MSU, Runkle also researches how different light environments affect orchids, some of which make their way to his second floor office in the Plant and Soil Sciences Building at MSU.

Lighting Up Profits can be purchased online at the MeisterPro website:

Runkle’s other research interests are described on his MSU faculty website at         
Geoff Koch is the communications
manager with the MAES (Michigan Agricultural Experiment Station of MSU).

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