I need to kill earthworms.
February 9, 2016 6:20 PM   Subscribe

How can I kill all the worms in a potted plant? I'd like a solution that does not require me to replace the soil (i.e., I'm A-OK with using chemicals for this).

I thought that putting earthworms in the pots with my plants would be a cute idea. Well, when I pulled a dead plant out of an 8" pot and discovered dozens and dozens of worms inside, it occurred to me that I may have caused a serious problem for myself. I have a couple heavier pots that I'd rather not muck around in again. Please tell me there is something I can mix with water and pour in that will solve my problem the easy way?
posted by BuddhaInABucket to Home & Garden (11 answers total)
Why don't you just put the pot outside and liberate the worms, Buddha?
posted by nanook at 6:37 PM on February 9, 2016 [21 favorites]

Wet cardboard on top of the soil overnight should bring them to the surface, then you can pick them off and take them outside.

If you have that many worms in a small pot, the dead worms will become their own gross problem.
posted by momus_window at 6:41 PM on February 9, 2016 [5 favorites]

The easy way to deal with this would be to ignore it; I've experimented with doing it on purpose, while doing apartment composting. Nothing bad ever came of putting earthworms in potted plants here.
posted by kmennie at 7:52 PM on February 9, 2016 [4 favorites]

If the basic problem here is that you wound up with so many earthworms you're skeeved out, I don't think you can kill the earthworms without your apartment reeking of decomposing earthworms. If one plant died, it's not likely that the worms killed it but the living conditions (i.e. too much moisture) that accompanied them for whatever reason, but since you invited them I think take all the plants outside, empty the worms and the soil they made in a nice cool spot under a tree to burrow down and live their lives, take the pots inside, wash them thoroughly, and go buy new plants.
posted by A Terrible Llama at 8:35 PM on February 9, 2016 [4 favorites]

Yes, an overpopulation of earthworms in a potted plant can kill it. (Also, composting worms are different than earthworms.)

The easiest solution is probably momus_window's wet cardboard method of luring them out.

There's plenty of advice on the internets about killing an overabundance of earthworms, mostly related to lawn care. However, most of those recommendations (Sevin, vinegar, etc.) are going to also damage or kill your plant, because they remain concentrated in the pot due to less opportunity for dilution and breakdown of the chemicals .
posted by desuetude at 10:02 PM on February 9, 2016

when I pulled a dead plant out of an 8" pot and discovered dozens and dozens of worms inside, it occurred to me that I may have caused a serious problem for myself.

What problem would that be? I have never, not even once, seen earthworms in a plant pot do damage to the plant.
posted by flabdablet at 10:10 PM on February 9, 2016 [1 favorite]

Also, composting worms are different than earthworms.

People using dedicated vermicompost rigs typically use a particular species of earthworm, Eisenia fetida (usually called "red wiggler"), because they are hardier and reproduce quickly. I can tell you from over a decade of bin composting, though, that ANY earthworms (and insect activity in general, even maggots, if you can tolerate them) are good for your soil and for compost. They are breaking down bits of food, digesting it, liberating parts of it for microorganisms to digest and, in the case of earthworms, adding their highly-nutritive-to-plants dung to the mix.

Basically, a good indicator of healthy soil is its ability to support life. People killing earthworms may do it because they're grossed out by them, but there's no intelligent reason to do this. No bugs = sterile soil, devoid of the nutrients that plants need to survive.

So, just take the plant out of the pot, knock the soil off of the roots over some soil outside, empty out the worms, and repot. I'd be very surprised if the worms are the culprit here (is the plant potbound? Being watered enough and otherwise getting adequate moisture? Getting the correct amount of sunlight? Many more likely possibilities) though.
posted by ryanshepard at 4:30 AM on February 10, 2016 [7 favorites]

Response by poster: So the general consensus is that I should let the worms live? I did a little additional research and it looks like maybe my desert rose is either dormant for the winter or else the last cold snap angered it. The Aralia was perhaps over-watered considering the amount of sun it was receiving.

Hey worms, you get a reprieve.
posted by BuddhaInABucket at 6:36 AM on February 10, 2016 [1 favorite]

Eponysterical. Peace to the worms.
posted by penguin pie at 7:27 AM on February 10, 2016 [4 favorites]

In general, worms dehydrate and die off a bit more easily than plants. Stop watering, especially if your plants have a dormant season. Give it until you feel your plants are approaching dangerously dry (but not serious danger) then do the wet cardboard trick and it should be a pretty potent worm lure.
posted by aimedwander at 8:03 AM on February 10, 2016

> What problem would that be? I have never, not even once, seen earthworms in a plant pot do damage to the plant.

They can get overzealous with all that digesting of organic matter, and damage the roots. A few are fine, of course. "Dozens and dozens" in an 8" pot is possibly more worms than the limited amount of potting material can happily support.

Yes, potted plants should have healthy enough soil to support insect life, and no, earthworms probably didn't kill the plant all by themselves, but the overpopulation may have contributed to the weakening of the plant. I've been container gardening for the better part of 10 years, growing a LOT of food, much of it in smallish pots.

Red wigglers are eisenia foetida, as you mentioned, ryanshepard. Common earthworms/nightcrawlers are lumbricus terrestris.

Here's an article from SF Gate on the subject of worms in potted plants.
posted by desuetude at 2:31 PM on February 10, 2016

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