The Sweet Fern versus Poison Ivy Antipathy

Sweet Fern vs Poison Ivy

Here is a rare True Fact: poison ivy NEVER grows along with sweet fern. These two plants just don't get along, and I have no idea what is behind this.

(Sweet is not a fern, but a small shrub, Comptonia peregrina.) 

The photo shows a growth of sweet fern on the left side of the rock, and poison ivy approaching from the right. This is as close as I have ever seen these two plants. In all the 55 years I have been noticing poison ivy, I have never seen it grow along with sweet fern. Other plants grow intermingled with poison ivy: Virginia creeper, blackberry, other ivies. But never sweet fern. 

sweet fern

I suspect that something prevents these two plants from growing from the same spot: maybe sweet fern puts something into the soil that prevents poison ivy from growing. For that matter, perhaps sweet fern prevents other plants from competing with it in some chemical way. 

(There are quite a few poison ivy remedies using sweet fern, so the antipathy between these plants carries into other areas.) 

I would love to know more about this. For one thing, sweet fern is a lovely shrub, and planting it might be a good way to keep poison ivy off your land.

If anybody knows more about sweet fern and its anti-poison attitude, send me a message via the contact page.