Sword Fern's Secret

by Green Deane

in Beverage, Edible Raw, Miscellaneous, Plants, Vegetable

Swod Fern's Water Storage Swelling

Nephrolepis cordifolia: Edible Watery Tubers

Edibles are often right under your feet, or my feet as it were.

I had a yard of non-edible ferns. If you like fiddleheads that’s an irritation. That irritation in time lead me to buy a regional fern book to seek out more fiddleheads than I already knew. To make sure I could ID ferns well I started with the ones in my yard, Nephrolepis cordifolia. From the other side of the world they were first found growing in Florida beside a road in Sumter County in 1933.  They have since covered much of the state.

Sowrd Ferns From Nepal Found In Florida in 1933

As the N. cordifolia does not produce much of a a fiddlehead I ignored it for some eight years as it spread, covering half my property.  The identification was rather easy in that of the five Nephrolepis in the state the cordifolia is the only one with marble-size tubers growing off its roots. In fact when I wanted to move ferns to a new spot I often planted the tubers. I thought nothing of them.

My research led me to a scientific paper on the plant from Nepal, Nutrient Analysis of Nephrolepsis, Kathmandu University Journal of Science, Engineering and Technology, Vol 4, No 1 (2008). A team not only tested the Nephrolepis cordifolia for nutritional content but reported children there eat the tubers raw all the time, apparently their favorite wild snack. The team recommended the tubers be investigated as a potential commercial crop. After rechecking my plants I suddenly realized I had thousands of ferns with edible tubers.

This was a win win in disguise. Florida put the N. cordifolia on the state’s plant pest list, the only fern of about 100 to make it. The state doesn’t like it because the fern is squeezing out the native Nephrolepis exaltata, which is a commercial product.  While many ferns species have useable rhizomes only two Nephrolepis  have tubers and both are edible, N. cordifolia \N. undulata.  What that means is if you have a Nephrolepis and it has tubers you have an edible. If you don’t live in pan-tropical regions around the world, no problem. There is probably a pot of sword ferns in any number of businesses and lobbies near you. Gently pull the fern root mass out of the pot and look for tubers. If it is a sword fern (Nephrolepis) and it has tubers, it is edible.  Often the N. cordifolia is sold as the N. exaltata because folks don’t know the difference. So you could have fern tubers near you.

Research on the Nephrolepis can be confusing. While online references say there are about 30 species of Nephrolepis in the world a recent study suggests 19 or so, read some consolidation and parsing happened.  There still may be some future sorting out in that not all agree there are 19 species.  A Florida botanist is quoted on a site as saying there are four species of Nephrolepis with tubers. I contacted him and he flatly denies ever writing or saying any such thing. That is why contacting primary sources is important. The Internet is just a place to start your research. It is not the place to end it.

Nutritionally the tubers of the N. cordifolia are 13.42 percent carbohydrates, 1.34% protein, 1.25 percent starch, 14.88 percent crude fiber, 6.53 ash, 0.75 percent calcium and trace phosphorus. They’re also about 96% water. They can range in color from cream to yellow to dark tan or brown. To me they taste similar Jerusalem Artichokes with the same crunch, a varying amount of astringency, water and potato-like earthy aroma. From the plant’s point of view the tubers are for water storage. The fern is often an epiphyte growing on other plants, most noticeably on palm trees. The tubers can provide water for the dry spells.

Nephrolepis (nef-roh-LEP-iss) is Greek and means kidney shaped scales, referring to the shape of the spoor packets on the back of the fern’s leaf.  Cordifolia (kor-di-FOH-lee-uh) means heart-leaf. Where each leaf (pinnule) attaches to the stem (rachis) there is a little protrusion that looks like the bottom of a heart.  Identifying ferns is often nearly microscopic in nature. You definitely need a hand lens at least 10x and a lot of patients.  The plant is native to Australia and the Himalaya areas. It is found in the Society Islands, New Zeland, Puerto Rico, Hawaii, Florida, Georgia, Alabama, and protected pots elsewhere. If you have a “Boston Fern” in might be the N. cordifolia. Look for the tubers. See my video on said.

Other ferns species with reportedly edible tubers include Angiopteris evecta, Diplazium esculentum, Cyathea medullaris, Pteris esculenta, Gleichenia dichotoma, and Marattia alata. Pteris aquilinum and Aspidium filix tubers have been used to make beer.

Green Deane’s “Itemized” Plant Profile

IDENTIFICATION: A medium-sized, medium-green, Boston/sword Fern, tapering to both ends,  producing below ground scaly round  tubers. Leaves pinnate, fertile and sterile fronds similar to three feet long and three inches wide; petioles to eight inches long, Forty to 100 leaflets on each side, oblong-lanceolate with a heart shaped lobe stem end of leaf; leaflet entire to slightly toothed, underside spore packets kidney-shaped

TIME OF YEAR: Tubers are available year round. The plant produces a horizontal root (rhizome.) Off the rhizome are wiry roots, stolons. Growing on the stolons will be the tubers. I think calling them “tubers” is not exactly correct, more like water storage units.

ENVIRONMENT: Shady areas, lawns, waste ground, limestone ledges, wet places, roadsides, in palm trees.

METHOD OF PREPARATION: Eaten raw, out of hand. If you roast large ones in a slow oven the turn into sweet, chewy lumps. Small ones keep their shape but turn to a powder inside that tastes like coffee.

 

 

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{ 14 comments… read them below or add one }

Matthew March 26, 2017 at 22:36

My boy has informed me that he has eaten the little balls on these ferns (which dominate the ground under my oaks) and his verdict agrees with yours. None of the humans at my house have eaten the leaves, but my chickens *love* them. Of course, the chickens love to eat roaches too…

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Sara October 26, 2016 at 14:38

What about Nephrolepis Obliterata (Kimberly Queen fern). In seeing a this sword fern in the store I discovered marble sized tubers. Are these edible? Are there any tubers in the Nephrolepis Family that are not edible?

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Mayumi Megia October 10, 2016 at 06:20

Are you referring to the tubers on the method of preparation?

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Green Deane October 11, 2016 at 15:08

Yes I am referring to the tubers. Nothing else is edible.

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Brandon Edward Cravey December 27, 2016 at 16:20

My child decided to put tuberous sword fern in her mouth. Took a bit of research to figure out that it was the fern, but it fits the description. Tuberous roots, overlapping slighlty toothed leaves, spiney rachis with dark attachment points. She did not swallow, only chewed the leaves. Are the leaves toxic?

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Green Deane January 4, 2017 at 05:58

That I do not know… I can’t recall any mature ferns leaves being eaten.

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Ralph Arnold June 9, 2015 at 23:27

Hey, if you will dig up and mail me a bunch of fern tubers, I gladly would repay you for costs and efforts.

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Wadeen Baribeau May 2, 2015 at 00:55

I love the article on the Sword Fern with tubers or water pods. I just had to remove quite a few ferns and have lots of the little marbles; was wondering how I tell if I actually have Sword Ferns or are there other ferns with this root tuber that are NOT edible? I am in Bradenton, Florida. Also, do you remove the outer layer before eating and how can I best store them for later eating?

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Green Deane May 2, 2015 at 17:20

There are five species of sword fern in Florida, but only the one we want puts on these water-swollen stolons. I rub the hairs off but don’t peel them. THere will store a while as is but dehydrating them is the best way.

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Sheila April 24, 2015 at 11:37

How do you plant the tubers? We just dug up a dead fern that did not make it through the winter and found the tubers. I found you as I was trying to identify what in the heck these things were. Do you know of a way to winterized the ferns? Most winters here would enable them to live, but the past 2 winters have just been too harsh. Thank!

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Green Deane April 25, 2015 at 07:28

I just bury them an inch or so because they are not tubers but swollen stolons, usually near the surface anyway.

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Connie September 18, 2012 at 14:30

If the small ones taste like coffee, could they be used as coffee grounds maybe? Sounds like an interesting experiment.

Also, are there any poisonous varieties?

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Julie August 21, 2012 at 21:29

Are there lookalikes that you’re aware of?

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Green Deane August 27, 2012 at 14:32

If you referring to this particular species, technically no. But ferns can be hard to sort out.

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