Gardening on the Planet

Doug Tallamy disproves opposing myths about native plants

DougTallamyDoug Tallamy, everyone's favorite entomologist/native-plant advocate, is one of the contributors to a new book about sustainable gardening (edited by Tom Christopher, and to be reviewed here soon). First he makes the case that if you care about insects, the birds that feed on them and, heck, all of nature, you'll grow some native plants, dammit, not just lawn and a few foundation plants. Nobody makes that case better than Tallamy.

He first made that case to the general public in his popular Bringing Nature Home,  published in 2007, and he's had time to observe reactions to it and to the native-plant movement generally.  For example:

There are many misconceptions about using native plants as landscape plants, but one of the most pervasive is the fear that natives will be defoliated by the very insects we are trying to attract with them.  After all, that's one of the reasons "pest-free" plants from Asia and Europe appear to be the logical choice.

I've heard that one, but what I've heard and read much more often is the exact opposite claim – that native plants are the "pest-free" ones because they've evolved in harmony with the pests, etc.  Which is hard to square with the urgings that we plant natives so the native insects can eat them, which they certainly do.

But guess what – both myths are wrong!  According to Tallamy, native plants attract plant-eating pests but they also attract a diversity of predators, parasites and diseases that keep insect populations in check.  Sounds great, but can he prove it?

Yes, indeed, he can.  He convinced one of his grad students to make a study of insect damage, comparing "traditional" with all-native landscapes – six of each.  After two years, the result was that only a tiny percentage of leaves were damaged on EITHER of the properties, with 1.5% of the leaves showing sucking damage and 4.5% chewing damage, both far below than the 10% damage threshold shown to be needed before homeowners notice it.  And the difference between the native and mostly-nonnative landscapes was statistically insignificant.

This study not only levels the pest-damage field between native and nonnative plants but does it in a way that avoids the messy questions about whether the pests are native or nonnative.  It simply records evidence from actual gardens in the 21st Century.  Thank you, Dr. T!

Posted by on August 16, 2011 at 4:39 am, in the category Gardening on the Planet.
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13 Responses to “Doug Tallamy disproves opposing myths about native plants”

  1. Abby says:

    Mirrors my experience, e.g. I have Japanese beetles in my yard and while they do some damage, it is not worth getting excited about.

  2. Jen. says:

    And, perhaps I need to look at the book, but does he differentiate between true natives or native cultivars (I hope I’m stating that correctly). Any thoughts?

  3. susan harris says:

    Jen, I don’t believe he mentioned cultivars in this article, but he may have in his book, Bringing Nature Home. Anybody know?

  4. I love science. We need a “Garden Mythbusters” show.

  5. donna says:

    is the study online somewhere? some us read that sort of thing.

  6. Frank Hyman says:

    I think I recall some discussion in a magazine about natives vs. native cultivars. Generally, a few studies show that the cultivars produce less nectar than the original species, so in terms of supporting pollinators, it seems likely that cultivars may be less valuable.

    Which that’s a general truism about any highly bred creature–you can breed to gain some characteristics–bigger flowers, longer bloom period, etc.–but you will lose some other characteristics along the way: less disease resistance (roses), less drought hardiness, less deterence to deer, less food value for pollinators, etc.

    Same applies to highly bred animals, but don’t get me started :-)

  7. Eileen says:

    This is a book that I’ve been meaning to get for a long time. Thanks for the reminder.

  8. susan harris says:

    Donna, here’s an article about the study, but it was on-going at the time – no results yet.
    http://www.udel.edu/udaily/2009/jun/plants062209.html

  9. UrsulaV says:

    As far as I know, it really depends on the cultivar. Some of them aren’t different enough to be significant, but anything where you get the double flowers and so on—like those awful new coneflowers that you see bred into powder puffs—tend to be rather less useful for wildlife.

    I suspect that cultivars are one of those cases where you have to actually watch what the bugs do on a case-by-case basis. My various hyssops are mostly hybrids of the native giant blue hyssop, and I can’t say the bugs favor any of them over another, whereas they seem to much prefer Solidago “Fireworks” over “Little Lemon.”

    At this stage, my own feeling is that we can’t let the perfect be the enemy of the good—if the average gardener is willing to plant cultivars of native species, I’m gonna praise them for doing so, and not demand anybody go to straight species.

  10. Jen. says:

    Thanks for the information. I’m not going for perfect (it’s a garden, there is no such thing) but trying to re-establish a vacant lot in the city. Luckily, the neighbor just took down the Tree of Heaven (?) tree, but knocked out all the nice volunteer natives/weeds in the process. If only I could conquer the Rose of Sharons…

  11. Good information brief – so many, many benefits to using native plants you and others have covered, depending on the situation or the audience we try to reach.

    Too bad many regions’ native species are used ineffectively (design principles often go out the door w/ natives and in “xeriscape”) or nurseries don’t grow/sell them to compete with habitual exotic plants.

    Oh well, another business opp’ty/gold mine!

  12. Dave says:

    I’m sorry, I couldn’t resist responding to Desert Dweller. First, there are no gold mines in the horticulture or landscape businesses. Incomes and profits are very modest, but the work is rewarding, I think. Over the past few decades every large company or Wall Street investment group that has decided to “go green” has given up and moved on the browner pastures after a few years because the profits are Mom-and-pop and not investor friendly.

    Second, ask one of the many native plant nurseries about their income in comparison to others who are selling mainstream (non-natives and select natives) plants, and they’ll tell you that their’s is a niche market, and a small niche at that. They’re not going to get rich. Not now, and probably not ever.

    A vast majority of marketing dollars go towards annual flowers and other colorful non-natives. There’s still a small fortune to made with the few people who are attuned to natives, you say? I’m afraid that the dollar bills confirm that there are far too few native purists to support a substantial business.

  13. sue dingwell says:

    I talked with Doug specifically about cultivars when he was the keynote speaker for our Florida Native Plant Society conference three years ago. His answer aligns closely with Ursala’s observation. It depends on what the cultivar was selected for and how it was handled afterwards. If it was selected for just a height characteristic for instance, then in all probability, it retains all the beneficial qualities of the original native. However, if it was selectively cultivated for anything that changed the leaf chemistry, like flower color, then value to wildlife is lost; those awful coneflowers being a prime example.

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