Sunflowers: don't play well with others!

[thistlebloom]

I was just doing some reading up on companion plantings and discovered something I had never heard about.
Apparently sunflowers have an allelopathic substance in their roots
that inhibits the growth of other plants near them.

The research indicates that not all species of plants are equally affected, but the one that stood out to me was the effect sunflowers had on potatoes. They actually work to stunt each other and sunflowers can result in potatoes being infected with phytopthera blight.

This was such bad news to me because I have run my sunflowers through the shredder for the last few years( I grow lots of sunflowers) and tilled them into my beds. Last years potato crop was weak, which I blamed on the weird
summer weather, but now I really think that the sunflower residue had a hand in my poor results.
Even worse to me was finding out that the allelopaths can remain in the soil for a couple of years,as I have tilled residue into all my beds.

I may plant my spuds on top of the ground this year.
I'm hopeful that the large amount of shredded leaves that I also tilled in and the good rains and large amount of snow this winter may work to leach some of the toxins out, or at least dilute them
enough that they don't stunt my other crops.
I love sunflowers and plan on growing a lot again this year, but I'll be pulling any volunteers in the main beds, and the suns will have their own area. Also the residue will go into the long term compost piles that I just heap and let sit for years in the woods.
Just thought I'd pass this on in case any body else plants suns in their beds with other stuff.
BTW, some people commented that they always grow suns with their other stuff and haven't noticed anything detrimental.
However, I would for sure keep them away from the spuds, and not plant them in any beds you were going to rotate spuds into next year.
The good news is that they are researching their use as weed suppressants.

 

[hoodat]

Sunflowers also stunt green beans.

 

[Collector]

That is good info to know. Hope the soil in your garden Will be in good condition this year! I am sure it will be. Thanks for the tip.

 

[Greenthumb18]

thistlebloom,

That's interesting how sunflowers inhibit the growth of certain crops nearby. I'm concerned about this since I had sunflowers with my potatoes last year as well. And I didn't get a good harvest of potatoes, maybe that's why.
I did some research and sunflowers actually help increase the yield with corn if planted nearby. Maybe its just where you plant them that will determine if their good for companion planting.


http://www.ghorganics.com/page2.html

 

[thistlebloom]

Yes, it is interesting how some plants are affected more than others. I thought this was interesting:
"However, studies with other species have reported that the response to allelochemicals may be concerning on the concentration dependent. Allelochemicals that inhibit the growth of some species at certain concentration might stimulate the growth of the same or different species at different concentrations (Narwal, 1994)"
That was found here:
http://www.ijat-rmutto.com/pdf/JUNE_v4_n1_08/IJAT2008_18_Ashrafi.pdf

It gets kind of technical and it's a long article, but it is interesting.

 

[Ridgerunner]

Nice thread. Good topic. Thanks.

 

[Chickie'sMomaInNH]

the only thing i know to plant with sunflowers that likes them closely nearby as a companion is cucumbers. they have the allelopathic chemicals in them as well but it seems they inhibit the growth of weeds. i have an old copy of 'Carrots Love Tomatoes' from 1992 so it may be slightly outdated.

 

[RustyDHart]

I've found a great Sunflower combination planting that looks wonderful and works well together. Sunflowers and Morning Glorys.....I plant the Sunflowers about 10 days before I plant the Morning Glorys next to them in the same row(s)....the vines will slowly creep up the growing stocks of the Sunflowers like a natural trellis. Planting them at the same time will have Morning Glorys growing up and beyond the slower growing Sunflowers....The Sunflowers NEED the head start. The combo...big yellow heads with the blue flowers trailing up the green stocks and leaves is beautiful.... With the various colors of both flowers...the combinations are endless.... Give it a try!

 

[journey11]

Well there's something new we've haven't talked about--cool topic!

Good to know, because I have a habit of sticking sunflowers in any bare spot I can find in the garden. LOVE 'em, just wouldn't be summer without sunflowers!

Greenthumb, I think you're right on the corn. I had mine next to some corn last year and the corn on that side bore larger, fuller ears than the corn on the far side. All other conditions were the same.

Now they also neighbored some tomatoes, but I didn't notice any trouble there.

I wonder on the part about composting them if the effect is worn off by then. Winter wheat also inhibits the growth of weeds by the same manner, but it is commonly used as a cover crop. Something to look into anyway...

 

[thistlebloom]

I wonder on the part about composting them if the effect is worn off by then. Winter wheat also inhibits the growth of weeds by the same manner, but it is commonly used as a cover crop. Something to look into anyway...

I wonder about that also, but to be safe this years sunflower residue will go in the long term compost (that just means the big pile in the woods that I don't turn ). It seems that the leaves have more of an allelopathic effect than the other parts, stems were the least allelopathic.
But where I erred was in shredding the entire plants and tilling them in to my beds in the fall.
I think if you just grow them here and there in beds you wont get a buildup of the toxins.
But for sure keep them away from potatoes!
It's interesting also that apparently cukes can cause phytopthera blight in potatoes.
I have the greatest space in my garden devoted to potatoes, they are probably what I consider my most important crop, so this info was a real eye opener to me.