Are sunflowers toxic to other plants? - Ask Extension
Last year I planted a few sunflowers (3-4) and this year that's turned into 15-20, while I was out giving them a bit of water my neighbor came and tol...
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Are sunflowers toxic to other plants? #841339
Asked July 18, 2023, 2:47 PM EDT
Last year I planted a few sunflowers (3-4) and this year that's turned into 15-20, while I was out giving them a bit of water my neighbor came and told me I should pull them up because they'll kill the other plants I'm growing. Google searches seem to be inconclusive.
Deschutes County Oregon
Expert Response
Josh:
To be honest, my first thought was, no way. I love sunflowers and have them in my garden, along a fence I want to cover, every year.
My research found otherwise! First, sunflowers work for good purposes, in that they have been found to remove toxic chemicals from the soil. Obviously they are great for pollinators, birds, and adds lots of color to our summer landscape. On the other hand, to ensure their survival, they employ a competitive strategy called "allelopathy". The sunflower, along with other plants that employ this method, release allelochemicals that cause growth inhibition to surrounding plants by affecting physiological processes such as respiration, cell division, and water and nutrient uptake. Symptoms of "allelopathic effects" include stunting, leaf wilting and yellowing, or death of part or all of a plant. Who knew?!
The effects are temporary, but if you notice the surrounding vegetation is not thriving as it has in the past, your volunteer sunflowers may be to blame.
I'm going to attach an interesting article about allelopathy and other forms of "plant warfare" you may find interesting...
Plant Warfare
Thank you for your question. I love learning new things about the plant world.
To be honest, my first thought was, no way. I love sunflowers and have them in my garden, along a fence I want to cover, every year.
My research found otherwise! First, sunflowers work for good purposes, in that they have been found to remove toxic chemicals from the soil. Obviously they are great for pollinators, birds, and adds lots of color to our summer landscape. On the other hand, to ensure their survival, they employ a competitive strategy called "allelopathy". The sunflower, along with other plants that employ this method, release allelochemicals that cause growth inhibition to surrounding plants by affecting physiological processes such as respiration, cell division, and water and nutrient uptake. Symptoms of "allelopathic effects" include stunting, leaf wilting and yellowing, or death of part or all of a plant. Who knew?!
The effects are temporary, but if you notice the surrounding vegetation is not thriving as it has in the past, your volunteer sunflowers may be to blame.
I'm going to attach an interesting article about allelopathy and other forms of "plant warfare" you may find interesting...
Plant Warfare
Thank you for your question. I love learning new things about the plant world.
