by Jeff Gillman, associate professor of horticulture at the University of Minnesota, who writes quarterly reports of horticultural research that gardeners can use for this website.
Over the past few weeks I’ve had a bunch of people e-mail me to tell me that I’m wrong about something or another. From the heresy I commit when I remark that applying commercially bought mycorrhizae probably isn’t going to help newly planted trees to my inexcusable audacity in commenting that commercial hydrogels haven’t worked very well in the tests I’ve conducted, it seems that some people just don’t like it when I don’t endorse their pet product. Most point out their own experiences, some point out other research, mostly unpublished and so unattainable by me, and some just tell me I’m an idiot. I like the last group best – they’re the most entertaining.
The thing that most people who voice these objections don’t understand is that I believe they should do whatever they want with their plants. If they think that hydrogels work because their Tarot card reader told them it does, then I strongly encourage them to use hydrogels. If they want to use mycorrhizae, then please, be my guest, use mycorrhizae. But I’m a professor with an Extension Service appointment. What that means is that my assignment – my job – is to transfer research-based information to those who can use it. There’s not much more to it than that. I take the research conducted by other researchers and myself and I make it available to the public. If most of the research that I can find doesn’t demonstrate that something works, then I’m not going to say that it does, but that doesn’t mean that I don’t think you shouldn’t try it for yourself (with some exceptions for safety of course).
The reason for this little diatribe is that the first paper in this research update is on mycorrhizae, and it concludes, yet again, that purchasing commercial mycorrhizae is a waste of your time and money. Now before you start e-mailing me, please note that most research shows that naturally occurring mycorrhiza are a very good thing that we want in our soil. Unfortunately, most research also shows that commercial mycorrhizae you purchase from a store are not useful. And off we go.
NEW STUDIES
1. Mycorrhizae
Our first research paper showed that applying commercially available mycorrhizae to maples and magnolias didn’t do much at all, at least not much that could be considered good. I like this quote from the paper “Commercial [mycorrhizal] inoculants are generally marketed based on the assumptions that they will increase root and shoot growth after transplant. In the present experiment, inoculation tended to decrease the former and had no effect on the latter.” The decrease in root growth wasn’t a big deal, but it certainly didn’t help.
2. Value of Landscaping
In an interesting survey of residents of cities in the Pacific Northwest it was established that good landscaping around a strip mall could entice consumers to pay 8.8% more for goods than they would pay in a strip mall with poor landscaping. (Did you know that the first strip mall was the Country Club Plaza in Kansas City, Missouri and was built in the 1920s? How’s that for a dubious distinction? I’m not a strip mall lover myself, except that some of my favorite restaurants are in them.)
3. Plants in Classrooms
In a who-would’ve-guessed type study, researchers in Texas established that students like it better when there are plants in the classroom and that these plants had the most effect when classrooms didn’t have windows. It’s important that I point out that student grades didn’t increase with the addition of plants in the classroom, just the course and instructor evaluations. Anyone want to guess how I’m decorating room 415 Alderman Hall next fall?
Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He’s also the author of two books, “The Truth About Garden Remedies” and “The Truth About Organic Gardening” (Timber Press).
