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How to deal with invading ferns

The four-letter word on our farm is “fern.” Mention it, and more familiar expletives may follow.

“How can you denigrate this lovely plant?” I ask my husband, Eliot, pointing out the maidenhair fronds that float gracefully above our shaded stone path. I’ve shown him how nicely the right ferns can hide the bare-naked stems of tall lilies, and how they soften the stony floor of our woods with a restful green.

But to a farmer, while any weed is a trial, ferns are a scourge. Their roots tend to be dense mats that are hard to bust up or pull out, a procedure that often leaves small parts behind that will soon regrow. They also scatter spores, the fern version of seeds. Some, such as bracken fern, also called brake (Pteris aquilina), are even allelopathic, leaching toxins into the soil that keep farm crops or pasture grass from growing. (All of them do that, Eliot claims, with scorn.)

I will admit that I have cursed some lacy species such as a hay-scented fern (Dennstaedtia punctilobula) that fetchingly crept into a groundcover planting and then choked it out. Last summer, an as-yet-unidentified fern marched into our blueberry patch, clearly intent on regime change. It took all my strength to pull it out — or most of it, which is the best I can hope for until it is finally gone.

One thing we both agree on is that removing the green growth of any plant will eventually kill it. Ferns can be dealt with by repeated mowing or cultivating, by burning, and by salting them to make your cattle devour them. File that away. Whichever method you use, it is best to do it before the ferns let fall their spores. That’s the science behind Thomas Tusser’s advice in his 1557 poem “Five Hundred Pointes of Good Husbandry.” He wrote, “In June and in August, as well doth appeere, / Is best to mowe Brakes of all times of the Yeere.” A 1915 Department of Agriculture bulletin called “Eradication of Ferns From Pasture Lands in the Eastern United States” backs him up.

In case you can’t tell when your pest ferns are about to drop their spores, I’d advise digging or mowing them just after they have come up and fully unfurled their fronds. When they come up again, repeat.

This is the time of year, of course, when ferns’ tightly curled fiddleheads poke up out of the ground. For some, this is a cause for great excitement. Certain species, including bracken and ostrich fern (Matteuccia struthiopteris), are considered edible delicacies, their “woodsy” flavor the taste of spring itself.

My resident fern-hater calls them “weird and probably toxic.” Actually, they are considered a bit toxic if eaten raw, so the standard advice is to boil them for 10 minutes first. Some species are suspected of being carcinogenic, and some are endangered, to boot. Maybe there’s ferns and there’s food, and never the twain should meet.

Damrosch is a freelance writer and the author of “The Garden Primer.”

Barbara Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”



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