The Goldenseal Rule: Low Light Promotes Growth
Written November 26, 2002
The goldenseal rule: Low light promotes growth
A little shade goes a long way in the growth and marketing of some woody plants.
Ohio State University ecologist and horticulturist Martin Quigley and Department of Horticulture and Crop Science undergraduate student Stephen Mulhall found that variable shading affected the root length, bud development and rhizome mass of goldenseal -- a herbaceous perennial sought after for its medicinal benefits.
"The typical agricultural procedure is full sun for everything, and while some woodland plants such as serviceberry perform well in direct sunlight, most have optimal growth under low light conditions," Quigley said. "Goldenseal requires a certain amount of shade to grow well, and we wanted to see what percentage of shade produces the best results."
The researchers conducted a yearlong greenhouse experiment with five different shade levels ranging from 60 percent to 95 percent full shade, plus a control group in full sun. Results revealed that goldenseal plants grown under 60 percent to 70 percent shade produced longer and more numerous roots, more buds, a greater rhizome mass and healthier leaves than those plants growing under 95 percent shade or in full sunlight.
"The plants in the full sun just got scorched, while those in the shade were green and happy," Quigley said. "The results of the study tell me that with all other conditions -- soil moisture, nutrient levels -- being ideal, goldenseal is just adapted to a woodland ecosystem."
Quigley said studies that help nail down the growth characteristics of woodland plants educate growers that some plants cannot be grown like agricultural crops. But they can contribute to forest preservation.
"A hundred years ago 95 percent of Ohio was fields. Today, 45 percent of the land is forested again," Quigley said. "Growing woodland plants for an economic gain is a good thing for a temperate forest because one can make money with the forest without having to cut the trees down."
Goldenseal is similar to ginseng and black cohosh in that it demonstrates medicinal properties, and is widely popular in Asian markets. The native Appalachian forest plant contains bioactive compounds, such as the alkaloids hydrastine and berberine, which boost the body's immune system to fight off colds and flu.
"Natural compounds tend to be gentler on the body than synthesized chemicals, but one drawback is that you can't control the dose as precisely," Quigley said. "That's another advantage to this research. If we can control the shade requirements of plants, like goldenseal, then maybe we can eventually standardize the proportion of active compounds present in the plant."
Quigley said the next logical step in research is to measure the development and concentration of active compounds under various shade treatments.