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Weeds between Patio Stones & Organic vs Conventional

Controlling weeds between patio stones is now very difficult; and a new study finds organic produce is not superior to that produced by conventional means!
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

August 2, 2009

Above, our waterfront deck early in the morning; the adjacent ornamental fence to exclude deer--note our unique gate I made this year; two of our indoor plants, Yesterday, Today and Tomorrow (Brunfelsia australis) and Cape leadwort (Plumbago auriculata) as seen from our deck; and a nice display of lilies at my office door. Below: hardy water lily ‘James Brydon’; a delightful pink Calla lily also in the large pond; hardy water lily ‘Barbara Dob-bins’ and our newest guest in the large pond sitting on our porcelain tugboat; and a close-up of our guest frog. Author photos.

A question from Alan Salmon in Ontario, to Donna, has ended up on my machine here! The question is a common one, to which there is no real good answer. “What’s the best way to permanently kill grass and weeds that grow between paving tiles.”

Ontario Premier Dalton McGuinty’s dumb pesticide law means there is literally nothing that can be used that will do the job “permanently” or even for an entire season. The only products available are acetic acid or acetic/citric acid formulations such as Greenstar’s Elimaweed or Scotts EcoSense (may be found as Ecoval’s EcoClear).

Sorry, but I have no better answer for you!

While I have a couple of other questions here, and I should deal with them, instead I will attempt to answer them directly to the enquirers, and then include my responses in next week’s column.

* * *

This week I want to make some comments on an old favourite topic of mine: organic vs. conventional methods of growing food plants. This is prompted by the release last week of a report from Britain’s Food Standards Agency an independent agency set up by the British Government. The study found no significant differences in the nutrition content of organic food compared with conventionally grown food. In reporting on the study, Canada’s CTV network said the following:

“The study was a systematic review, or meta-analysis, of dozens of studies on organic foods, published over the past 50 years, and was conducted by a team of researchers from the London School of Hygiene and Tropical Medicine (LSHTM). The researchers say they found more than 52,000 articles on organic food, and narrowed them down to 162 studies analyzing the nutrient content of organic versus conventionally produced foods.

“They found no evidence of a difference between organic and conventional crops in terms of their content of a number of nutrients, including: vitamin C, magnesium, calcium, potassium, zinc, and copper. Conventional crops were found to contain more nitrogen than organics, and organic crops had higher phosphorus and acidity content than conventional crops. Among animal-source foods such as meat and milk, the researchers found no evidence of differences in nutrient content.

“When nutritional differences were found, they were so small as to be insignificant, reported the paper's principal author, Dr. Alan Dangour, of the LSHTM's Nutrition and Public Health Intervention Research Unit. A small number of differences in nutrient content were found to exist between organically and conventionally produced crops and lives-tock, but these are unlikely to be of any public health relevance.

“Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority.

“The findings are published in the American Journal of Clinical Nutrition.

“Gill Fine, FSA Director of Consumer Choice and Dietary Health, says the study does not mean that people should not eat organic food. What it shows is that there is little, if any, nutritional difference between organic and conventionally produced food and that there is no evidence of additional health benefits from eating organic food.”

This is just one of the aspects of the organic vs. conventional, and a discussion (argument) that will likely never end. I have no particular care which system gardeners use in their own gardens, I just repeat that gardeners in general should be aware that no plant can tell the difference in its source of nutrition; i.e. the plant does not know whether its nitrogen (or phosphorus, or potash) came from an organic source or a chemical source. Generally, fertilizers from chemical sources are much cheaper that those from organic sources. And, on the other side of the argument, fertilizers from organic sources are much better for the garden’s soil than are those from chemical sources. However, the latter ‘problem’ can be at least partially be set aside by continually applying organic additives such as Canadian sphagnum peat moss, Coir and home compost to the garden soils.

Many pro-organic, anti-chemical fertilizer folks say that chemical fertilizers often spread far beyond the area to which they are applied; although a 40-year study I cited in 2002 ( ) stated there was little if any indication of nitrogen leaching as a result of home lawn fertilizing over a 40-year period! Check it out on my site!

On the other hand, “organic production allows natural pesticides, which can be toxic to humans and wildlife,” says Alan McHughen, Ph.D., professor of botany and plant sciences at the University of California, Riverside. Organic fertilizers may also contain harmful bacteria, such as E. coli.

One only needs to think back as far as the Walkerton Ontario tragedy of May 2000 during which seven residents died and at least 2,500 became ill due to E. Coli contamination of a farm well. This contamination was directly linked to manure application (organic fertilizer!) to farm fields. In subsequent reports and court results (up to three-plus years later), two brothers who managed the city’s water system were found guilty (of Common Nuisance which was a plea bargain), and a percentage of the blame was assigned to the Conservative provincial government of the time for having ordered certain cutbacks.

Yet another factor in the organic vs. conventional farming techniques is that organic farming yields only 75 to 90 percent of the crop of conventional systems, meaning that more land must be planted in order to have an equal return.

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