FOR THE LOVE OF BRACKEN FERNS ...Just Not in the Garden!

Copyright 2026 Lori-Ann Willey

I’ve always thought bracken ferns were as beautiful as any other fern.  Their shape is unique and always loved how on hot days, I could crawl in a patch, lay under the frond canopy, and feel a little bit cooler.  As I grew older, though these ferns, in some areas, could be quite tall (up to 6 feet-ish), I learned it depends on the area and nutrients in the soil.  Even as a child, I realized the ground where they grew was always hard, dry, and barren of undergrowth, or nearly so.  A few short 4” plants with dainty white flowers and shiny leaves seemed to be about the only plant that grew around the brackens.  I’d observe them as I relaxed away from the sun…or a quick rain shower.  As an adult, I’ve continued observing these ferns, but far more so after we purchased our camp in 2004. They are everywhere here!

Bracken ferns are tough, aggressive plants that easily take over an area and stop neighboring plants from growing. The canopy I mentioned above easily chokes out much of the sun so nothing much can grow on the ground beneath them because they suck up any moisture and nutrient value in the soil around them.   When they die back in the fall, the mat-like crunchy fronds form around the plants preventing other seeds from ever touching the dirt. As if all that wasn’t selfish enough, they play a chemical/toxin warfare game as well!

These ferns release natural poisons that leach from the leaves into the soil, which actively stops new seeds from sprouting and stunts the roots of existing plants. Their impressive underground rhizome root systems can grow twenty feet long, allowing them to steal most of the water and nutrients from the soil while at the same time turning the dirt highly acidic -a condition that most backyard vegetables cannot tolerate.  Hence, where these ferns grow, my plants do not!  This act of selfishness is why I’ve studied and observed these ferns over the past several years.  I used to leave them in my garden because they are pretty.  However, where they grew, my vegetables and greens did not.  I used to blame the soil, but I made so much compost that is PH balanced, made fish hydrolysate, etc. etc. that I didn’t understand why my seeds didn’t sprout there when the same seed packet would germinate in other beds.  If they sprouted, they were severely stunted and bolted quickly.  Then, I remembered as a child how barren plant life was underneath the canopy of brackens. 

Though the moment of realization brought back a fond (or, frond) memory, I wanted to knock myself up beside my head for not realizing my garden issue sooner. 

Fortunately, you can turn this troublesome weed into helpful garden fertilizer if you process it correctly to destroy the natural toxins. Burning the ferns into ash instantly destroys 100% of the toxins, leaving behind a material packed with potassium that helps flowers and fruits grow. If you prefer to throw the ferns into a compost heap, the pile must become hot to destroy all the poisons in about three to four weeks, whereas a cold compost pile will require at least twelve months of rotting before the mixture is safe to use. If you simply pull the ferns out of the ground and rake away all the dead surface leaves, the poisons already left in the dirt will naturally wash away within one to three months.  Unfortunately, in Maine, especially in this part of the state, that’s the growing season for many garden plants! 

There is yet another problem with hot composting the brackens to kill the toxins, and that is a compost pile that gets too hot, will also kill off beneficial microbes that the soil and plants need!  To kill off the toxins in brackens, the compost temperatures must be between 131F - 140F degrees for about 3 weeks.  That’s not an easy thing to do here in our part of the state, which is why I often cover my compost piles with “clear” plastic to help heat up the piles.  The problem with this is the plastic can produce too much heat and kill off not only the bracken toxins, but also the microbes needed for a soil that supports life.  Without microbes, you have dead soil.  Microbes start dying off at about 130 degrees.  The danger-danger zone is between 130-140 for most microbes, and certain death at 160 degrees.  So, for those wondering why I turn my compost piles so often, now you know why.  I have it all down to science and second nature at this point.

Because bracken ash is highly alkaline, contains zero nitrogen, and is packed with potassium, it must be applied to garden plants very carefully. Leafy greens like lettuce and spinach should never receive bracken ash because they require nitrogen to grow big leaves, and excess potassium will make them turn bitter and grow seeds too fast.  That’s what was happening in my leafy green beds -why I kept moving my greens year after year while allowing the brackens to grow with them to offer shade.  Dee-dee-dee!  I should’ve made that link sooner, but nope.  I didn’t.   Also, soft herbs like basil and mint will suffer damaged root chemistry and yellowing leaves if exposed to the ash compared to woody herbs like rosemary and thyme love alkaline soil, and a small handful of ash in the spring will strengthen their stems and improve their flavor. Flowering morning glories also benefit from a tiny bit of ash because they bloom best with low nitrogen, allowing them to produce a large number of bright flowers.  That’s the mistake I made last year, but now I know.  I thought it was because I planted them in partial sun.  I was confused when a friend of mine had beautiful and numerous morning glory flowers and mine showed no sign of even wanting to bloom.  I blame the brackens!  

While confirming all my suspicions and observances, I learned something new.  Not only does the bracken fern hog moisture, nutrients, make the soil quite acidic, keeps its competitors away, I learned that once they produce spores in August-ish, that one must never touch, cut, or burn bracken ferns in late summer, especially during August, because the leaves release tiny dust spores that cause serious health problems if inhaled through smoke or air.  I wonder how many times I’ve been affected by those spores and haven’t had a clue!  I’m always in the brackens!  Come to find out that it is only safe-safe time to handle the plants when they are brown and dead during the winter or early spring.  Otherwise, the toxins safely inside the stems are harmless to humans.  Digesting is toxic to both humans and animals, so it shouldn’t surprise you to see even the animals leaving these ferns alone.  

So, now, I simply break the stems at ground level when I see them in the garden.  Unfortunately for me, but fortunate for the plant, this will not kill bracken ferns because of their root system that hold great energy reserves and will quickly sprout new plants! To permanently kill the root system without chemicals, you have to manually snap off every new green shoot as it pops out of the ground.  This act starves the roots and eliminates the plant completely after two to three years. I still love the bracken fern, just not in my garden!  I’m getting there!