For publication in the February 2009 Takoma Voice newspaper.
Composting of all types is finally catching on, and that includes vermicomposting – employing worms to turn your kitchen scraps into black gold. Seattle and other progressive jurisdictions are even distributing worm composters to their residents. But mention of these industrious recyclers increasingly leads to the question: But aren’t they invasive? Well, some are, in some situations, but confusion abounds and unearthing the 411 about which ones and where is easier said than done. Not that that stopped me from trying.
First, what’s not to love about a critter who returns organic waste to the earth? And not just kitchen scraps, either. Rachel Carson wrote about worms being used to remediate pollution by removing toxins from the soil. Municipal sewage systems are using worms to remove harmful bacteria in human waste and turn it into clean biosolids – a great substitute for synthetic fertilizers on farmland. Some ranchers are using worms to compost the tons of animal waste that would otherwise be polluting our waterways.
On organic farms, the castings of another type of worm – the earthworm – not only increase soil fertility but have been shown to reduce plant disease, without the use of chemicals. Studies show yields increasing by 20 percent after earthworms are added to growing fields. Even for the home organic gardener, worm castings provide essential nutrients and have fungicidal properties that can fight mildew and other diseases. Then there are the soil-aerating benefits from earthworms’ constant burrowing, which helps improve both water retention and drainage.
Invasive Worms Damaging Northern Forests
Yet there ARE destructive worms in the U.S. During the last ice age, glaciers covered about half of North America and wiped out the earthworms in their path. Above a certain latitude the forests evolved without earthworms until the introduction of worms from elsewhere, brought there in cargo or carelessly discarded by fishermen, and these invaders are changing the forests. Authorities in Minnesota, the leader in fighting to protect Northern forests, explain that these nonnative earthworms are changing the structure of the soil and therefore the ecology of forests. Worms eat the thick layers of leaves called "duff" that covers the ground, turning it into richer soil, which affects what plants can grow in it, what insects that can live in it, and right up the food chain. Ultimately these worms may could cause some plants and animals to go extinct.
(Here in Maryland, below the glacier line, native earthworms were left intact. In fact, across North America there are today about 120 native earthworms, none of which seem to be sold as composting worms because they act so slowly.)
Night Crawlers are Bait
According to Minnesota’s top worm expert, Lee Frelich, seven types of worms have been found in their hardwood forests, including the European Lumbricus rubellus or night crawler. The evidence against this popular bait worm mounts, with both Cornell and Maryland having fingered it as the primary culprit. It and the other invaders thrive in unimproved soil and can survive severe winters. Maryland’s Extension Service goes on to say they’re NOT suited to compost bins and will die in them – as will Maryland’s native worms.
Red Wigglers are Composters
The red wiggler or Eisenia fetida, another European import, is the primary species sold for composting purposes. Unlike the night crawler, the red wiggler thrives in organic waste, lives close to the surface, and can’t survive temperatures below 40 degrees or above 90 (the ideal is 70-75). Where winters are mild they still only survive outdoors in compost bins or heavily mulched gardens that are rich in organic matter. But as composters they’re ideal – they eat, excrete and breed quickly. I learned that the red wiggler "has not been found outside of compost in Minnesota. They can’t survive being frozen." The Brooklyn Botanic Garden website agrees that they’re not a "problem species." Maryland’s Extension Service says these worms "do poorly" in average soil, and Virginia reminds us that composting worms like the red wiggler are not an "earthworm" at all. Now can we relax hire these guys to do some composting for us?
Weird or Confusing Advice about Worms
Unfortunately, a recent New York Times article on invasive worms cited night crawlers and an Asian species as the harmful species, then concluded by telling readers not to "toss out fishing worms or red wrigglers by throwing them on the ground or in a pond." Then the author described for urban readers how to capture and kill worms in their yards…but didn’t mention any evidence that worms are actually doing harm in cities (and I couldn’t find any). Other authors recommend using only "native species of compost worm," which is totally unhelpful, since there are no native worms suitable for composting, according to the University of Minnesota. No wonder there’s rampant confusion.
The public is often advised to consult their local Extension Service to see if earthworms pose problems in their geographic area and which species are causing the difficulty, though many of them simply don’t have an answer. And one online source even suggests that readers "consult relevant scientific studies". Again, good luck with that.
Despite state officials in Minnesota having cleared red wigglers as a potential menace there, Minnesota ecologist Cindy Hale tells composters to freeze their worm castings in air-tight bags for a least a week before adding them to garden soil, no matter what worms species they use. "It won’t hurt the soil microbes, but it will kill all the worms."" But composters tell me this turns castings into hard chunks that are impossible to spread. She’s not the only authority recommending the freezer treatment so we can all compost "without fear of spreading invasive worms" – apparently not aware that "composting worms" aren’t the problem.
For outdoor composting, the advice is even weirder. Sources warn against adding "extra earthworms" to outdoor bins… but does anyone buy worms to add to their regular compost bin, anyway? Minnesota advises that "If you have a compost pile in a forested area, do not introduce additional non-native earthworms." Makes sense but really, people do that?
Advice that make sense
Buy composting worms from a source that knows what it’s selling – and it’s red wigglers. One supplier, WormpostNortheast, which only sells red wigglers and even uses the Latin name for them, warns their website readers about avoiding night crawlers, again using common and Latin names - hooray! Suppliers should also state clearly what temperatures are tolerated by the worms they sell; otherwise people with subfreezing winters might buy red wigglers and leave their bin outdoors, only to discover a worm graveyard after the first hard frost. The use of the term "redworm" by some suppliers is particularly confusing, since it’s applied to several species.
Amy Stewart, author of The Earth Moved, a highly entertaining book about worms, adds this advise: Don’t dump any compost or mulch in wooded areas. That’s because this additional organic matter causes an unnatural increase in the population of earthworms – non or nonnative – which alters soils, and consequently plant and animal life in the soils.
Favorite Indoor Vermicomposters
I polled worm-composters across the U.S. and most agree that layered compost systems are the best because they separate worm castings from worms and uneaten food, making harvesting of castings much easier. Commercially, brands like Can-o-Worms, Worm Chalet, Worm Factory and Gusanito sell for $65 to $160. Do-it-yourselfers can save money and make a layered system in 30 minutes using Rubbermaid bins for $20, plus the cost of worms. (Google homemade worm composter for directions.)
Though several sources advise against plastic bins, most composters use it and have no problems. Others advise against using newspaper as bedding material within the composter, but again most people use it and report no problems. But when it comes to buying the worms themselves, everyone seems to agree it’s best do it in spring or fall, and those are the only times that responsible suppliers will ship them.
For more information Wormwoman.com and Wormdigest.org are great sources.
Photo credit: Red Worm Composting.
{ 27 comments }
Hello!
I stumbled along your blog and as a budding gardener myself i enjoy reading through this to give me ideas!
Also i am having a Seed Bomb Workshop this sunday if you are interested!
Wow! Very interesting…I had no idea that there are invasive worm species. I have been considering starting a worm farm myself and find your article useful, thanks.
A very detailed article indeed, should be a nice addition to the Takoma Voice newspaper. I have just stumbled across your blog and am really taking the sustainable gardening messgae to heart. At the moment I only make my own compost, however would really like to try other sustainable techniques such as worm farming. It should really help with the large vegetable garden I have been planning.
Susan, thank you so much for this article — very helpful in explaining the invasive/composting worm problem. I am thinking of starting a worm farm, and I plan to spend part of this snowy day while I am stuck in the house in googling for how-to-build-your-very-own.
Susan, I heard about invasive worms through a Bayscaping class a few years ago, but little detail was given. Thanks for doing all this research – very informative!
SCARY stuff! I am just about to launch my major composting initiative! Have been scouring the neighborhood for cast off wood scraps. In fact, I think I might take a bike ride to find some, and then go around with the car to pick up what I find! I have decided that I am probably not going to go with worms right now. I don’t think I can handle the responsibility! However, if I did, I would go with a tray system like you describe above. Did you see the guy at GWA with the worm farm trays? That looked like the best way for me.
Thank you for the super information!
Susan, many thanks for this. I’m giving a children’s presentation at the Northwest Flower & Garden Show & am thrilled to have this information. Kids always have the toughest questions, and this will help me provide more answers if they’ve been introduced to all of the confusing/conflicting info out there. Thank you!
Thank so much for helping to clear this up, Susan! Excellent editorial detective work!! I know I’ll be using this info.
Susan-
Thank you! Thank you for the well researched information! This article is FABULOUS! I am sending everyone over here to read it.
I too was confused and I so appreciate you taking the time to weed out the fact from fiction. Well done!
Theresa
Whether they are native or not, worms find their way into my outdoor compost piles and do a great job. I’ve never had to add worms to the outdoor piles. A worm bin is a different story. Red wigglers are sold for these. Worm bins can be created from Tupperware or plastic containers. The worms don’t care. But separating the worms from the castings can be complicated when it comes time to harvest your “black gold.” That’s where the “worm hotels” work best. They are usually three or more stacking layers. You just lure the worms into the next layer and harvest the castings from the layer they’ve vacated. To my mind, the extra cost is worth the price. A worm bin will easily live in a coat closet with no mess or odors and the worms will take care of all your kitchen scraps.
What a fantastic service you have provided. This clears up so many things and sets the record straight. And the links!!!! Great! I have always admired worms but not until I became a master gardener did I learn about raising them. Well, that is all I needed to hear. I just had to have a worm hotel. I am on a fixed income and in a small apartment. So I decided to make the hotel out of a small 3-drawer plastic storage cabinet that I picked up from goodwill for $5. It is about 3 feet high and about 18″ wide. This made it easy to handle. I could just pull the drawers out to put in my straps. It had rollers on the bottom so I could move it around if I needed to. I painted it black to keep out the light and put holes in the bottom of the top 2 drawers for drainage and all around the top of each drawer for ventilation. Then I just filled the top two drawers with straps that I saved in a plastic baggie in my kitchen sink then added my red wigglers. I watched the bin like a mother with a new born. Besides some fruit fly issues the bins started working like a charm. I was waiting to get enough castings to make a tea. It only took about a month then I did an “All hands on deck here comes the water” run.
When I need fertilizer for my plants I just pour water into my top drawer and let it run down to the 2nd drawer that drains into the empty bottom drawer. This is a beautiful rich and concentrated worm tea. I take the bottom drawer out (small enough to handle) and add extra water to it. It is now tea time. I get a coffee can dip it in the tea and start passing it around to all the ‘good’ plants. I can almost hear them sighing in absolute delight.
And I have had babies in my worm bin! How cool is that? They must be happy. Everybody needs a worm bin. For waste disposal, fertilizer, compost, it is just magical what these little guys can do with scraps. There is another link for kids called Squirmin’ Herman the worm. Just too cute. Teaches them (and me too) all about worms. Did you know they have 5 hearts? I actually have a little Herman sticker on my computer. Why? Because I am a silly old woman that is just having too much fun raising worms for heaven sakes. Here’s the link. Grand babies love it. http://www.urbanext.uiuc.edu/worms/index.html
Again, Great Post. Thanks.
Jeanne: I am SO with you. Ditto, ditto, ditto to everything you said. Especially this: “I watched the bin like a mother with a new born” and this “Everybody needs a worm bin.” It’s almost like a religion with me. And I have these fantasies that worms could (a) solve the world’s energy crisis, (b) solve the world’s global warming crisis, (c) solve the world’s financial crisis, and (d) bring us world peace. Well… maybe (c) and (d) are a bit delusionary but not (a) and (b).
I know, I know. Do you walk with your nose to the pavement after a rain and pick up all those little guys that get stranded on the sidewalk? A fantasy that I have entertained for years is that they are immortal. Do not die of natural causes. I do not know if it is true or not but I think this is where my first notion that they might be supernatural came into play. We are in a class all our own Pam but singing their praises seems to do the soul good.
“Immortal”! You’ve raised them to deity status which I admit is one step ahead of me. But I’ll ponder this notion and see how it feels. I highly recommend that you read Darwin’s book “THE FORMATION OF VEGETABLE MOULD THROUGH THE ACTION OF WORMS
WITH OBSERVATIONS ON THEIR HABITS. ” It’s online at http://www.gutenberg.org/dirs/etext00/vgmld10.txt. It’s really quite fun to read and very accessible, even to a non-scientist. I’ve been printing it out in chapters to read, but I think I’ll go ahead and order a copy from Amazon. Done!
I would say many earth worms introduced to northern forests came from nusery stock: b&b trees and shrubs, potted perennials. We know how it is, leave something on the ground with goods to eat and the worms find their way in, or they are simply dug up with the worms in the soil. Nobody adds worms intentionally, they come on garderners’ coat tails. Can anyone really imagine eliminating them. Can we imagine native worms not making it north either?
Worms are here to stay. Its as if we may then say to those in the sub and ex urbs that they shouldn’t garden because they will introduce non-native worms. They’ll have to raise everything from seed in order to avoid introduction. I can see the local nursery tagline now, “All perennials, trees, and shrubs grown locally, in worm-free soil.”
Fantastic blog Susan! I’m so glad I stumbled upon it.
A word of caution about vermicomposting…do your homework.
I know someone who killed all their poor worms because the bin got too hot.
Thanks for clearing up a lot. I’ve known for years that night-crawlers are horrible for the Eastern forest. Around here (cincinnati) they’ve eliminated the duffy layer. Just gray, hard “soil”. The leaf-fall cover after October usually doesn’t even last through late Spring to protect the soil from rain/erosion. The crawlers turn all that organic stuff into – you got it – CO2. Worst invasive we have, bar none.
Don’t use native worms. Check, got that.
Buy only red wrigglers. Check, got that.
Worm bin or tupperware do-it-yourself. Check.
Don’t put your worm castings in the woods. No, problem, since no woods around here.
Keep worm bin out of reach of nosy, invasive schnoodles. Hmmmmm. Going have to work on that one.
When I explained vermiculture to my husband (of 48 years of marriage) and said that I was considering setting up a worm farm, his comment was:
At your house, or mine?
Hmmm. Methinks there are some unsaved souls around these here parts.
I keep my worms in homemade farms (not rubbermaid, IKEA – I’m swedish
) in the understairs closet. Unfortunately I’m not watching over them like a mother over her baby, actually I’m rather careless – but they do fine anyway. Red wigglers are sturdy.
Thanks for that, very interesting. Have been finding it difficult to find appropriate information over here. I will also follow the links.
Go worm power!
Regards Joley
An interesting and informative post.
Thank you.
Fascinating post! One tiny addition is that sometimes you can get away with using locally collected worms, which means that you at least can’t introduce any species into the environment that weren’t already present. I had very good luck with my Can O’ Worms bin in the Seattle area though I stocked it with worms I dug up in my own garden. Most likely the bin did well because many of the worms I collected were red wigglers, but I had a very healthy, active population of worms, and the worms were free. Now that I garden in Maritime Canada, I’m trying the same thing using the do-it-yourself version of stacked bins and, again, worms I collected in my own garden.
Thanks Wild Flora will give this a try. Since I had just a small 3 drawer bin I would sometimes have more scraps than my little guys could handle. So I found a patch of dirt outside, believe me my yard is about the side of a VW and dirt is hard to come by, and started a little impromptu compost pile. Someone had given me some red wigglers and before I could get my bin started I had to let them go. I was afraid they were going to die. So I threw them on the ‘compost pile.” I checked it the other day and it is very happy and lively. I am making a worm bin for a friend now and will take your suggestion and put these foot loose and fancy free guys to work in my new bin.
Hi Jeanne,
I too found that though it is fun to have a worm bin, a single bin may not be able to absorb all the kitchen scraps you can generate. I also found that the amount of soil produced, though well worth having, was not nearly enough to meet my garden’s needs. Except in cold weather, outdoor composting produces a lot more good soil and absorbs a lot more scraps. I find that the main use for my worm bin is as a source of tasty treats for my ducks, who are crazy for earthworms and don’t get much variety in their diet during winter months. Incidentally, if you have ducks they will be more than happy to dispose of any nightcrawlers you find in your garden!
OK..I live on thirteen acres in northern Minnesota….I have open and wooded fields…lot’s of oaks, birch, maple etc. My husband and I started our new garden last year..4 six by 12 feet raised beds. I have tons of worms and all soil tests came out perfectly balanced…..I am having a hard time imagining buying worms orrrrr trying to get rid of the ones I have. Are these worms invasive? They have been here longer than me! Signed….happiest outside!
Well, Raenee if you are asking me if your worms are of the invasive variety it would be hard to say without doing a physical on them. If you however are worried that the worms in your raised bed may be doing it some harm my opinion would be no. From the article above the invasive worms ate the “duff” and that was what was causing an upset in the ecology. In your case the worms are in the soil, in a raised bed and you have no ‘duff” therefore your worms, night crawlers or red wigglers, would not be contributing to harming the ‘duff’ environment. And you are right worms have been around longer than we have and I could almost guarantee they will outlive us all. If all your tests are coming back positive I would say your worms are doing a good job for you. They are somewhat of a captive audience in your raised beds and can at the very least keep your soil nicely aerated. To me it seems like a no harm situation and I would leave them be.
I am in California on the central coast and believe it or not there is a shortage of red wigglers for worm composters here. Suppliers have been swamped with requests as more and more information about all the benefits of worm composting comes on the wave of the green and sustainability movement. We did a show about raised beds ( episode 1 ) and worm bins ( episode 4) and have blogged on my experiences at holeinthefence.net. We filmed a TV documentary many many years ago for PBS (they didn’t buy it) called “Living off the Land”. We built a log cabin and started a garden off of the Gunflint trail in Grand Marais where my husband and his family grew up. My son was 18 months old at the time. He is now 36 and we are again doing a show, he is the host, about “Living off the Land” and my grand babies are in it. I guess you can call that the circle of life.
Anyway back to your worms. Count your blessings. And happy gardening. Jeanne (mom)
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