These days, everyone's promoting organic gardening and I'm on that bandwagon, too - what's not to love?
Turns out there's a problem with such a broad-brush approach as "organic is always safe" or even "organic is always better". And I know that because Jeff Gillman, professor of horticulture at the University of Minnesota, disabuses us of that notion in his book The Truth about Organic Gardening. As a researcher he's actually scrutinized the findings inn order to give us objective assessments of hundreds of products and practices. So we don't have to rely on marketing copy, much of which is simply hype. This kind of impartial advice has heretofore been hard to find - mainly on Extension Service websites, and only in the case of some states (Maryland's is thankfully one of the best).
As a rule, true believers in organic methods - the organic purists - don't mention the possible toxicity of organic products, or the fact that some synthetic or "chemical" products are only mildly dangerous, and sometimes less so than the organic alternative. On the other extreme, we can hardly take as gospel what the industry says about their products, can we?
But The Truth About Organic Gardening is about much more than competing products. According to Gillman, the the POINT of organic gardening isn't simply replacing synthetic products with organic ones. The POINT is to reduce the need for any products at all, by following the principles of organic gardening. Less fertilizer, fewer if any pesticides. Instead, he recommends focusing on building up the soil with compost and mulch, then choosing the right plants for the right site, and watering appropriately - because plants under stress are much more vulnerable to "pests" of all kinds.
The meat of the book, however, are Gillman's careful reporting of benefits, drawbacks and a super-helpful "bottom line" about the most commonly used pesticides and fertilizers. A sampling:
About Neem oil, Gillman says it's effective in killing insets, not so much in dealing with fungal disease. And it's destructive to aquatic life and has been linked to reproductive defects in rats - so Gillman is "somewhat hesitant about using it."
Does it work? This is fast becoming a hot item in the gardening world, and over on GardenRant Gillman has debated it extensively with the most outspoken proponent of compost tea, another Jeff - Jeff Lowenfels, author of Teaming with Microbes. (Here's the Lowenfels pro-tea article.) Compost tea results from percolating water through a sock filled with compost, which produces a liquid that's filled with beneficial bacteria and fungi, which gardeners then spray on plants to feed and protect them from disease. Gillman says sure, the plants benefit from the nutrients in the tea, but disputes the notion that tea confers any protection against disease. (This dissenting view of the disease-prevention abilities of compost tea is shared by another horticulture professor, Linda Chalker-Scott.) Gillman notes that there's also a risk of brewing up E. coli germs during the process of making the tea.
What the good professor has to say about Round-up (the best-selling herbicide containing glyphosate) may surprise you. He "respectfully disagrees" with those who consider it dangerous, citing its, noting that its Environmental Impact Quotient is pretty darn respectable (15.3 out of 100), lower than some organic products. Still, he's more a fan of hand-weeding and encourages readers to be less tidy in our gardens.
Organic products not so harmless: An important point in the book is Gillman's judgment that "Organic products can be as harmful as synthetics, or even more so," and he cites Rotenone as a great example. An organic dust that kills the destructive Colorado beetle, Rotenone may be a plant-derived insecticide but it's still highly toxic to aquatic life and links to causing symptoms Parkinson's disease-type symptoms in rats. "Why would any sane person use this pesticide?" Gillman asks."
On the subject of synthetic fertilizers, Gillman thinks they're fine if not overused - just once or twice a year is fine. More often than that will cause its salts to kill beneficial soil creatures. Still and all, he prefers using organic fertilizers for gardens (as opposed to farms, where maximum yield is a greater concern).
Much of Gillman's advice can be summed up as: Use common sense, read the labels, and follow the directions And like any proponent of organic, eco-friendly gardening techniques, he encourages us to tolerate a bit of imperfection in the garden - a few insect-bite holes here, a dandelion or two there. He says, "One of my favorite ways to deal with pests is by ignoring them."
Gillman also encourages and practices open discussion of best gardening practices based on actual findings, not superstition or ideological bias. But until all gardening advice is equally objective, (and we know that'll never happen!) I highly recommend having this book on your book shelf because else nothing like it exists, online or in print.