Ministry of Controversy

Is there proof? And do we care?

Sister
This quilt representing the Three Sisters is by M. Joan Lintault.

For decades, the theory of companion planting has been
common wisdom in organic gardening circles. We even feature a book about it on
our sidebar, Sally Jean Cunningham’s Great Garden Companions (it’s a fun read
too).  But every once in a while, a
minor debate pokes its head up—how do we really know this works? Has it been sufficiently
tested? Is there really any difference? (This discussion was recently in
progress on the garden writers’ listserv.) Our friend Linda Chalker Scott
prefers the term
 “plant associations,” because although she lists some tested benefits, she feels the term
companion has become too loaded down with anthropomorphism and pseudoscience.

There seem to be mixed results from field testing, but for
the average gardener, companion planting happily falls under the category of
“why not (what harm could it do).”  It is often used for vegetable gardening (mixing marigolds
and zinnias among the cabbage, for example), which would certainly make the
vegetable garden more attractive if nothing else.

One thing that I have found about plant diversity is that
roses mixed with perennials seem to do much better than roses alone. I’ve had
both and ever since I started adding more tall perennials, my untreated roses
seem to suffer less from the dreaded midge—against which there is no palatable
recourse.  But I have had less
success convincing my husband, who thinks that a big bed of all the same thing
looks peaceful and elegant. So even on the aesthetic side there is
disagreement—at least in my house.

Posted by on June 8, 2010 at 7:31 am, in the category Ministry of Controversy.
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19 Responses to “Is there proof? And do we care?”

  1. Katie says:

    When I managed the Children’s Garden at Fort Ticonderoga, we planted about 500 marigolds, lining all of the paths, and surrounding the entire garden.

    We had almost NO pest problems.

    AND, at that point, I was managing HUGE vegetable gardens with almost NO prior experience.

    I SHUDDER to think of some of the mistakes I made (hello rototilling the entire garden eVERY time we planted, thereby chopping up the worms, and ruining the soil structure)

    But, the plants were big, healthy, prolific producers, and almost no (bad) bugs, so we must have done something right :)

  2. Michele Owens says:

    I’m sure that certain plants repel certain pests. And I’m sure that there are some meaningful exchanges between plants. I believe that fungi have been shown to transports nutrients from legumes to certain trees.

    But I also think that until these relationships are proven scientifically, most companion planting advice is worthless superstition.

    It represents just more senseless complexity of the kind that drives would-be gardeners out of gardening.

  3. Kaviani says:

    It’s common knowledge and sense that biodiversity is critical to plant and soil health. If you only attract a certain set of insects or microbes, you leave your plants exposed. Complementing them with plants that attract beneficial insects, repel bad ones, accumulate minerals (as yarrow does), or fix nitrogen is a major boost.

    But then there’s allelopathy…gotta know your stuff.

  4. greg draiss says:

    One reason for roses doing better in a mixed bed than en masse is simple. A single rose is much less a beacon of light to midges than an entire bed. It has nothing to do with bio-diversity and other four dollar words ruining the gardening world. It’s just common sense. As THE TROLL, when I go shopping for new bridge to plunder, I want a huge selection of bridges to choose from not a single span alone by itself.
    It is just common sense. More roses equal more midges plain and simple.
    I am with Michele on this one. Quit the pyscho-babble erudite plant by the moon bio-crap nonsense and stick to gardening.

    THE TROLL
    BTW THE TROLL will be at the IGC in Chicago this August!

  5. commonweeder says:

    I forgot about marigolds this year, but I’m off to the seed rack now.

  6. Val says:

    I care, somewhat. A lot of companion planting just makes sense–e.g., attracting pollinators, repelling insects. However, as a beginner gardener who studied some botany, I know that some plants may complete chemically. The glut of online advice on companion planting is not well vetted. As a result, I keep most of my flowers out of my raised vegetable beds and hope the beneficials are getting drawn close enough.

  7. luise h. says:

    This year I underplanted my Tomatoes with Nasturtiums.If it keeps those pesky whiteflies away,great.But, it will look great and it’s a good use of space in the Containers. I do use Nasturtium Flowers in Salad.
    And I do not plant Onions or Leek next to my Asparagus.I did use Marigolds in the veg Garden before but I really hate how they look.

  8. Jenny says:

    Personally I think it is just wrong to restrict plants from being companions with other species. I don’t care what plants do in the privacy of their own (raised) beds!

    Oh…I see what you mean about the anthropomorphism…

    But the marigold thing is true. My Poppy told me.
    ~nod nod nod ~

  9. luise h. says:

    And we do know that plants have natural substances in their roots,their leaves and flowers as well that can attract or repel insects.So if I can use plants to protect other plants I dont have to reach for the dreaded chemicals.It’s a win for me.

  10. Jen says:

    Last year I planted “red rosie” romaine lettuce and noticed that it was untouched by slugs, but the rest of the bed was eaten up. I thought it might have repellant properties, so this year I planted it all around the perimeter of my raised bed. So far the red lettuce seems to be keeping the slugs out, except in one small area where the lettuce didn’t germinate. The cabbage leaves in front of that area are eaten!

  11. Kate says:

    I definitely have heard several times that marigolds are good to plant around vegetable gardens, but as far as my companion planting goes, I usually group my plants by watering and temperature needs. I’m not sure if they “technically” go well together or not, but it makes my life easier, and sometimes just happens that way randomly…I usually start in one corner of the garden with the cold weather crops and work my way out from there, for example.

  12. My entire vegetable garden is surrounded by plant associations so diverse it would take weeks of study to determine the full complexity of species. There are herbs gone wild, perennial and annual flowers of all kind and maybe a weed or two. Ha.

    http://outsideclyde.blogspot.com/2010/06/state-of-vegetable-garden.html

    Does it help? I do not have to worry about pollination. I don’t have problems with whitefly or aphids. Actual insect damage to plants past the seedling stage is nil. By the time I find the tomato hornworm it is usually covered in egg cases from parasitic wasps.

    Does it hurt? Every year I get the wilt on the cucumbers. The grasshoppers can be a pain in the seedling stage, the rolly pollies too, but they may really like the environment created by my wood chip mulch. I can’t grow any cole crops. No cabbage or broccoli, they just get covered in caterpillars. Some things are not deterred.

    What I would really like to hear about is a plant association that will repel that stinkin’ raccoon. Varmint!

    Other than that the human enhanced plant associations around the vegetable garden were already here and it’s traffic stopping pretty.

  13. Laura Bell says:

    I can handle the critters in the veggies for the most part. I tend to let things go to seed, which seems to pull in the beneficials & pollinators. I also like to interplant edible flowers (calendula, nasturtium, viola, etc), which do the same. But my fruit trees are another thing – anybody have a good “companion” for my Asian pear that’ll keep those goll-durn coddling moths out ?

  14. Gretchen says:

    We tried planting the three sisters early in our gardening adventures, and it was a mess. Nothing grew well and the mutant beans became fruitless monsters strangling the life out of the corn and squash.

    We’ve had the best yields with mono-cultures in our raised beds, but we’ve also come up with our own brand of voodoo for what works on our crazy property (it’s a swamp with the same ph as beer, and I’m not being hyperbolic.)

  15. Kaviani says:

    “It has nothing to do with bio-diversity and other four dollar words ruining the gardening world. It’s just common sense.”

    YES, fool, a bed of diverse plants and therefore diverse insects is BIODIVERSE. Don’t try to dumb it down because you don’t like big words.

  16. Adrian says:

    Nasturtiums and marigolds, OK. But don’t forget native plants and/or herbs that attract native pollinators.

    I think every edible landscape should have a patch or row of wild native forbs and grasses–great if you haven’t got room for a whole hedgerow.

  17. I complained in my blog about Park Seeds’ advising folks that planting a few marigolds would repel nematodes from tomatoes. Park wrote to me citing some references that they were correct. So I wrote to Linda Chalker-Scott who kindly searched the literature for me and found that most of the nematode repelling chemicals occur in the marigold leaves, so if you grow a cover crop and plow them under before planting tomatoes, it might make a difference in the nematode population. (Thank you Linda.) See http://www.sky-bolt.com/garden/#marigold-nematode for the entire exchange.

    So like many old gardeners’ tales, there is a bit of truth, but the efficacy has been exaggerated.

  18. sara says:

    I don’t know about proof, but my veggies grow a lot more readily when I mix them together in the plots. I am not three-sistering, but two-sistering. The squashes are a lot happier below the several types of beans and peas in the raised bed. And the corn transplants are growing faster than they did last year. I sowed beans in between them when they went into the ground last week.

    So far the tomatoes are growing well with beans sowed in their raised beds with them.

    And I have a lot of flowering sages to attract bees for pollination, which get moved around the yard.

    The primary reason I like to interplant is water useage. I plant closer together than a lot of books say is kosher, in order to take advantage of water.

    No aphids this year. The ladybugs discovered the yard in a big way and are all over the place, woohoo.

  19. luckwagon says:

    I used to plant marigolds next to tomatoes, like the plant experts told me to. But it seems no matter where I plant them, the slugs eat ‘em down to the stalk. Well, if it gets the slugs off the lettuce, so be it.

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