The correct spelling of the word is 'allelopathy' if you want to do some research. I have not heard or read of sunflower plants being allelepathic for poison ivy in particular, but there are other plants that are sensitive to the chemicals produced by sunflowers. Though allelopathic substances can be produced from roots, stems, leaves, etc., I don't think that there is any solid information that sunflower seeds are allelopathic. At least, not that I've seen.

Many, many plants produce a wide variety of 'plant to plant' toxins. I know that lots of problems in the landscape and garden are probably caused by this silent warfare! Even the small non-woody roots of huge trees can be affected by allelopathic properties of certain grasses and plants.

Would love to know where you read/heard that sunflowers were capable of control poison ivy.

Thanks for the answer and the correction. I do not remember where I found that article, it could have been an almanac or maybe 'Horticulture' mag, not sure. My husband is highly allergic to poison ivy and we had a patch 100 feet by 50 feet and was trying to look for a non toxic or least invasive method of killing it. We ended up using roundup, but attracted lots of birds with the sunflowers, and have never had a problem again with poison ivy. If I ever find the article I will post it. It has been at least 5 years since I read it.

I've read for many, many years that the hulls of sunflowers are allelopathic. But I always held a mild suspicion that the allelopathic effect might not be *that* strong and that distributors of sunflower seed for bird feeders were simply jacking up the stakes on the allelopathy in order to sell a more expensive product (sunflower hearts & birdseed mixes without hulls).

So far on the Web I've found references to the allelopathic effect of sunflower by Ken Roberts, Ketzel Levine, the Maine Audubon Society, and various University Agricultural and Cooperative Extension Services websites. But it's tough finding an acutal reference to any specific chemical - all references are to a vague "growth inhibitor" in all parts of annual sunflower.

Finally I found a site that at least looks like it had some scientific organization & actually describes different kinds of allelopathic causes... it's at The College of William & Mary.

About Poison Ivy I do not know. I'd suspect the Roundup did that. Otherwise people couldn't have birdfeeders in their gardens at all.

Here is a link that might be useful: http://www.wm.edu/biology/bio405/allelopathy.html

Strictly anecdotal, but the spot where i've had sunflowers for several years is barren, except for a little chickweed and stunted pigweed. I do think it's in the seeds, i grow sunflowers for the birds, and always leave the plants up through the winter, and they make quite a mess. THe areas around my birdfeeders are pretty bare, too, the grass dies, and not much else takes its place. I'm thinking i read that the sunflower seeds inhibit germination, including other sunflowers, but even things I've put in as plants don't do well in those areas.

My experience with sunflowers has been the same as lynnie's. I can't grow anything except weeds where my sunflower/bird feeder was. It was the feeder from haedes. The grass died. We dug the area out 5-feet and it still is the same. I put in a rose bed after digging it out. They eventually all died. I tried growing a Natchez crape myrtle there (practically a wild plant) and it did horrible. I have decided to make a pathway of that area and put pavers over it. Have to redesign the whole yard for a birdfeeder from seven years ago.

Hi Patricia, gardening always offers an opportunity to learn new things in one way or another.

I checked around that old apple tree today and the grass is growing well. No poison ivy. Flock of cedar waxwings though. Very pretty. It is nice to have some areas just for the wildlife, and your yard will no doubt benefit from them.

O.k. now you all have me worried!
I planted several sunflowers in the back of my flower beds for background. Also I have about seven that sprung up in my compost pile.
Should I be worried? Or should I just let them grow, then when they are done; yank them and toss them (not in my compost)?
Oh dear....

I guess you will have to ask someone else that question as I am no expert, but I can tell you what I would do. I would let them grow and attrack the birds, they are usually more benificial than chemicals, for body, mind and soul. I have often left the sunflowers grow from where they sprout and have not had a problem other than the poison ivy. Check with DorieinAlabama perhaps she has a more scientific answer. I have used roundup on several other things and they keep growing back, but not the poison ivy. [knock on wood]

Thanks. :)

Actually I've researched like crazy today. Finding that if sunflowers are in compost, the allelopathic properties are gone after wintering.

Then I found this cool page too:
http://www.ghorganics.com/page2.html

SUNFLOWERS: "Planting sunflowers with corn is said by some to increase the yield. Aphids a problem? Definitely plant a few sunflowers here and there in the garden. Step back and watch the ants herd the aphids onto them! We have been doing this for years and it is remarkable. The sunflowers are so tough that the aphids cause very little damage and we have nice seed heads for our birds to enjoy! Talk about a symbiotic relationship"!

Sure enough I went out and saw ants encircling groups of little critters and chowing down. It was strange to see. Guess I'll leave those ants alone. Usually I have a fit though because here fire ants are such an ordeal!

Poison Ivy is awful. It took my mom about four years to get rid of what her neighbors had growing on their fence. The were avid campers and somehow brought it back in their equipment. It spread along mom's back fence. Just awful!!

Thanks so much for the answer. Going away shortly and will not have a chance to check this for a day or two but it sounds very interesting. Sounds like we should all grow sunflowers for one reason or another.