To weed or not to weed

The environmental irony of St. John's Wort - and other noxious weeds with medicinal qualities

By: Pat Daley

  It's 1951. For the last 10 or 20 years, British Columbia farmers have been complaining about an invasive weed - one that travelled to North America with European settlers. It makes light-skinned livestock such as sheep sensitive to sunlight, causing blisters, sore mouths, hair and weight loss.
  Pesticides kill the weed but also destroy trees and other vegetation. And the weed is usually the first plant to come back after spraying. So, Canada makes its first foray into biological weed control and imports insects that are successfully controlling the noxious plant in California.
 

"There's no advocates for the plants themselves. We don't want to demonize these plants and exterminate them." - herb-grower Conrad Richter

  Fastforward to the 21st century, when clinical studies are showing the same weed has potential as a treatment for depression and a range of other ailments. It is becoming a valuable commercial crop. Its wild population - the culprit in making livestock sick - has been brought under control, but the insects that attack it are still around. And where the insect goes, a fungal disease that destroys the plant also has a tendency to appear.
  The plant is St. John's Wort. The insect is the chrysolina beetle; the disease is anthracnose.
  On the surface, this could be a good news story. It involves weed control practices that fit in well with moves like the drive to ban pesticide use in Halifax, which Straight Goods reported a few days ago (Breathing easier in Halifax).
 

The chrysolina beetle: where it goes, a fungal disease that destroys the plant also has a tendency to appear

  The problem, however, is that one person's weed is another person's medicine - and one that has the potential to become a big business. According to the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), medicinal herbs are a $321 million industry in Canada, growing at a rate of 15 - 20% a year.
  Last year, OMAFRA reported that Ontario was seeing its first major infestation of the chrysolina beetle. While the insect munches away on the plant, so far growers have been able to manage, says Conrad Richter, vice-president of Richters Herbs in Goodwood, Ontario. The problem is the disease the beetles appear to carry.
  Researchers at Nova Scotia's Acadia University found that plant mortality can reach 75% where both the insect and the disease are present. That's a lot of St. John's Wort, which can yield up to 1,200 kilograms per hectare in a market where prices appear to be on their way down.
  The irony in all of this is that people around the world are gobbling up a medicine made from what was once considered a noxious weed. In fact, it still can't be grown without a permit in some jurisdictions, such as Washington state, Montana, and California. Growers like Richters are not allowed even to ship seeds into California. This irony isn't lost on Conrad Richter.
  "One of things we get harassed about by government agents is that a lot of our plants happen to be weeds," he says. "There's no advocates for the plants themselves. We don't want to demonize these plants and exterminate them."
 

"As the demand for herbal remedies continues to grow, so will the need to balance the various interests concerned with these types of plants."

  One example he gives is purple loosestrife, the scourge of hunters, fishers, environmentalists, and anyone who cares about the destruction of wetlands. A major U.S. conservation group once wrote a letter complaining about the inclusion of the invasive plant in the Richters catalogue.
  "I wrote a pointed letter explaining that it's a very potent medicinal plant for strengthening the liver," Richter says. "They sent back an apology." But purple loosestrife is no longer in the catalogue.
  Another common "weed" is colt's foot, whose dandelion-like flowers should be appearing any time now. It's considered a noxious weed in Ontario, but it's also a popular remedy for coughs, asthma, and bronchitis. Richter's own municipality, Uxbridge Township, is planning to spray all ditches, where the plant is commonly found, in order to eradicate it. For Richter, it's a worst-case scenario: spraying a plant he believes does little harm in a place where water runs.
  Of the 23 plants on Ontario's noxious weeds list, 12 can also be found in Peterson's Guide to Eastern/Central Medicinal Plants - although several come with toxicity warnings. As the demand for herbal remedies continues to grow, so will the need to balance the various interests concerned with these types of plants.
  Dr. Peter Harris, an emeritus scientist at Agriculture and Agri-food Canada's Lethbridge Research Centre, maintains the department's biological weed control web site. He suggests anyone interested in growing St. John's Wort commercially go to an area of the country where the beetles have not taken hold.
  One place is above the 1,000-metre elevation level in British Columbia's interior where, he says, a ring of yellow is visible on the mountains. "All you have to do is harvest it," he says. The other place is Newfoundland. In parts of the country where the beetle is controlling but not eradicating St. John's Wort, people who want it for personal use should be able to pick it wild, he says.
  Alternatively, he suggests growers could use an insecticide in the spring before the bugs lay their eggs.

Pat Daley is a freelance writer and editor in Athlone in Simcoe County, Ontario who last summer lost her stand of St. John's Wort to anthracnose. But the beetles were pretty.

Get More/Do More
Interested in commercial herb growing? Find out about Richter's annual growers' conference at www.richters.com

Some provinces have growers' associations.
- British Columbia: www.bcherbgrowers.com
- Saksatchewan: www.saskherbspice.org
- The Fraser Valley Herb Society, Langley, BC: www.fvhs.cjb.net

The Canadian Herb Society is located at www.herbsociety.ca

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