Invasive Autumn Fern

 

Many of us have come to gardening already knowing the big invasive plants in Georgia: kudzu, privet (Ligustrum), mimosa (Albizia julibrissin), tree of heaven (Ailanthus altissima), English ivy (Hedera helix), chinaberry (Melia azedarach), and more. Some plants, however, are joining that list (or moving up in priority) even as gardeners plant them. Autumn fern (Dryopteris erythrosora) is one of those plants that people need to know about. Unfortunately, it doesn’t even seem to have made the list but it is listed in a publication called New Invaders of the Southeast (p.24).

Autumn fern in creek

A couple years ago I had a young autumn fern show up in my yard. It was right in the front shade bed, mixed among the native ferns. Autumn fern is easily recognizable in spring when new growth is bronze colored.  I removed and trashed that plant. 

This year, I noticed in my creek several evergreen ferns that appeared to be a type of wood fern (Dryopteris).  There were two large ones on the side of the creek wall and one small one on a rock in the middle. When new growth showed up, it was clear they were Dryopteris erythrosora.

Where are these coming from? Several folks have reported that the spread of this fern is facilitated by waterways. Spores and young plants get washed downstream, especially during heavy rains when creek banks are scoured by rushing water. Downstream they will get lodged into new areas and the infestation spreads.

While there is very little information out there on invasive spread, a paper published in 2018 specifically addresses the spread in Georgia. The paper is by Tom Diggs (professor at University of North Georgia) and H. Umstead (student). This paper was shared with me by Tom after an online discussion of this plant in 2021 after I found it in DeKalb. The paper discusses a population in Alpharetta, GA (not terribly far from me) but also documents some of the reported locations in Georgia and the southeast.

Autumn fern fronds

I have since removed those ferns from my creek and securely trashed them. I’m not sure where they originated since my immediate upstream neighbor doesn’t have them. I’ll be monitoring my creek more closely and I’ll be checking my neighbor’s section as well. Unfortunately, I don’t have access to monitoring downstream, but you can be sure that I’ll do everything I can to stop the spread in my area. If you find it in the wild, be sure to report it.

Please do not buy this fern, remove it if you have it (especially if near waterways), do not donate it to local plant sales. We’ve seen so many plants become invasive (ornamental pear, anyone?), if we could learn to stop things when they first start to show tendencies, we could make a difference.

Fronds are hairy and red

Sori on Autumn fern