sunflower allelopathy

Discussion in 'Fruit and Vegetable Gardening' started by finngreen, Jun 3, 2006.

  1. finngreen

    finngreen Member

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    Location:
    Sherbrooke, Quebec, Canada
    Hi,

    Does anyone know exactly how toxic sunflowers are to other plants? I've been looking for information on the Net and it varies tremendously. On the one hand you see things like "good companion plant for x" and on the other, scientific studies that have isolated toxins in the water that drips off the leaves! Some sites say it's the hulls that are the real killers, others say the roots exude toxic chemicals. I saw one site that said the toxin from the hulls would be gone in two months, and another that said farmers who grow sunflowers as a crop have to rotate them (probably not a bad idea for any crop...) because the toxins build up and actually poison the sunflowers themselves. And then there are sites about interplanting sunflowers with crops to kill the weeds -- but why doesn't it kill the crops?

    Anyway, I had what may end up being a 12-foot sunflower proudly planted in the middle of one of my vegetable beds and then I remembered that information, so I pulled it out and planted it in a container so it wouldn't poison my vegetables! But it would have looked nice in the middle of the bed. For future reference, how much damage would it do?

    Thanks for any input!
     
  2. Durgan

    Durgan Well-Known Member 10 Years

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    I have been growing sunflowers all over my gardens for years, and never even imagined that they were toxic to other plants. Certainly there has been no indication of such, or I missed it completely. I often let them grow where they pop-up just for the birds, and often dry the heads and throw them on the garden for the birds to strip in the late fall.
    Now I am slightly concerned but not panicking.

    Durgan.
     
  3. yellow_peach

    yellow_peach Member

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    Are you sure?

    I mean I put them everywhere between my vegetables too or rather I let them grow if they seed themselves.
    They look nice, the birds like them, kids too.
    And I am eating the vegetables, they really say it gets poisend if the sonfloers are in the same place?
    So the other plants don't die or stay small or whatever? they get poisend?

    Ok I think I need to do some research.
    But I won't stop eating my vegetables it simply tastes too good.
     
  4. Raakel

    Raakel Active Member

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    Goodmorning,

    Here are a couple links to scholarly publications that describe the allelopathy of sunflowers.

    http://www.jstor.org/view/00409618/di005028/00p0441k/0

    http://www.blackwell-synergy.com/links/doi/10.1046/j.1439-037x.2002.00526.x/full/

    One article states that phytotoxins (a toxin produced in a plant) are present in all parts of the sunflower. The phytotoxins either inhibited seedling germination and seedling growth. They also have an affect on crop yields. If the residues of the sunflowers are removed each year the effect of the phytotoxins is significantly lowered.

    Allelopathy in plants often provides a competitive advantage in order that other seedlings in the area do not grow and compete for water and nutrients. To me it is fascinating! Practically speaking I have not observed the affects of phytotoxins on plants in the vacinity of my sunflowers. However, I am not sure that I would plant sunflowers close to an area where I am seeding my vegetables or other plants. I would, however, plant potted plants in the area, perhaps restricting my sunflowers to the borders of the garden. I would also be sure to remove any sunflower residues at the end of the season. Most discussion about sunflower allelopathy involves sunflowers as a crop rotation with other food crops. I have not come across any indication that the phytotoxicity is harmful to humans, however, I will need to explore futher.

    Raakel
     
  5. finngreen

    finngreen Member

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    Hi again,

    Thanks for the responses. It seems there's a bit of a misunderstanding; I don't think there's any question of the sunflowers making other crops poisonous to humans, and that certainly wasn't my concern. I'm just worried about them preventing my other plants from growing. And it sounds like that isn't the case in your gardens, so maybe I'm worrying about nothing.

    I was unable to access the first article Raakel referred me to (I'm not a subscriber to the service); the abstract of the second one did seem to suggest that plants grown in a sunflower field the following year did not grow as well, even if the residues had been removed.

    If I understand you correctly, Raakel, you're suggesting that I could put plants I had started elsewhere in around my sunflowers once the other plants were past the seedling stage? In that case, I could have left my sunflower where it was, because I was planning to put fairly well-established pepper and tomato plants around it (well past the seedling stage -- the tomatoes are flowering!). Maybe next year I'll give it a try, seeing as none of you seem to be seeing any ill effects. Although I might not want to do anything that has even the remotest chance of weakening my tomato plants; they need all the strength they can get to fight off early blight!

    Anyway, I didn't mean to create a panic about sunflowers making vegetables toxic; NOTHING I have read would indicate that the toxins in question collect in the other plants or are dangerous to humans.

    Carol
     
  6. Raakel

    Raakel Active Member

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    Sorry about the link. I am working from a UBC computer and I forgot to consider that the article may not be accessible to others.

    Research suggests that sunflowers residues did reduce the yield of the plants. Although, because they are discussing crop rotation they are writing about a large number of plants which cannot really be compared to a small garden. I had trouble finding information about phytotoxicity in small doses. To be safe perhaps it is best to keep your tomato plants away.

    I am sure that your plants would have been productive sitting next to your sunflower, however, perhaps not as productive as they would be if they were located elsewhere.

    Raakel
     
  7. Kaviraj

    Kaviraj Member

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    Hi,
    My name is Kaviraj.
    I used to grow many sunflowers while living in Australia.
    The allelopathic relation to potatoes is well known.
    iIf you grow potatoes near sunflowers, they tend to rot or go glassy.
    That is the only relation i know of.
    Residues never affected my plants.
    I used to pull out the young ones when about 1 metre high and use them as green manure, without any negative effects.

    Btw,
    I wrote a book on homeopathy and agriculture.
    Homoeopathy for Plant and Soil
    Available from Mark moodie publications or from Narayana Verlag In Kandern Germany
    more info at www.considera.org or http://www.narayana-verlag.de/
     
    Last edited by a moderator: Jun 9, 2010
  8. Bulldog71

    Bulldog71 New Member

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    So my wife planted sunflowers along our back fence. The back side of our garden is adjacent to the flowers and I planted cucumbers and squash. It looks like weed killer was sprayed on the plants, apparently run off from the sunflowers. We have had about an inch of rain a week for the last couple of months. The run off appears to be killing what were healthy vines.
     
  9. Zeke15old

    Zeke15old New Member

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    Old post so I'm not sure if anyone will see this. I planted sunflowers and tomatoes together. Tomatoes grew nice and green and flowered, then all of a sudden looked like they were hit with round-up. I was told they are similar to growing under a walnut tree.
     

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