Earthworms in Potted Plants? Do They Help? Leave or Remove?

Adding earthworms to houseplants might sound a good idea at first. However, earthworms are animals that provide areation and drainage benefits in an open space of an outdoor garden, less for indoor plants. Hence, should you add earthworms to potted plants? What about if you just found them? Should you get rid of them?

Worms can be beneficial for potted plants to fight compaction. However, the usually lower organic content, limited space, and fertilizer might harm them. There is no evidence of worms eating roots or damaging plants. Care is required to make such animals thrive in the confined environment of a container making them less attractive options for indoor potted plants.

It is interesting to notice that there is a significant amount of different opinions on the matter even among experienced gardeners that I will share with you in the following.

Earthworms and Potted Plants? Not the Best Companion

The most striking outcome of my research was the absence of a unique opinion on a subject, that, apparently is not as simple as it might sound. 

From one side we have those gardeners (even with decades of experience) that, no matter what, claim that worms are the best companion for any plant. On the other side we have another group of experienced gardeners, botanists, and even academics who claim that, in certain conditions, worms can be more harmful than good, especially for indoor plants.

I have been convinced by the argument shown by the latter for one simple reason. I totally agree that earthworms and plants evolved to be the plant’s best companions (helping each other). However, did this happen inside a 5-inch container? No! This mutual adaptation happened in open space with specific conditions that the confined environment of a container might not be able to guarantee at all times.

To better understand this concept I will guide you through the benefits (few of them pretty unusual) in having worms in your plant soil highlighting how, such advantages, might be a problem for an indoor plant:

Earthworms move through the soil mixing it as a consequence. This allows air to circulate and consequently roots to breathe very easily. This is extremely important for the well being of any type of plant, either in a pot or in a garden;

Earthworms usually eat decaying organic matter. This might be produced by decaying leaves, dead insects, or dead small animals (and their corresponding casting) when they land on the soil in the proximity of the plant. This material is all over the place in the open space of a garden.

Is that the same for an indoor plant?

The soil of an indoor plant is, almost by definition (as indoor) poorer in decaying organic matter. Indeed, you might remove dead leaves from the soil, you might not have insects around (we are inside a house) even less decaying small animals.

Moreover, the soil used for plants that you might find in the supermarket is really poor in such worm nutrients that in a more diverse and open environment are easier to be found. So you might likely end up with an indoor plant with a “too” clean soil from which worms cannot find enough food. 

Worms are natural “converting machine” that eats decaying matter and produce plant nutrients through excrements (yes, poop also called casting or worm manure). These are some of the best food for plants not for the presence of nutrients (that are relatively low) but more for the presence of healthy bacteria (whose importance has been mentioned in this article). These nutrients are also slowly released in the soil, positive aspects for the good growth of your herb.

However, for the previous point, if there is not much food around, the worms might not be able to produce the precious casting (and survive in the first place)

What happens in case the worms get too many? An open garden is not a problem as they have plenty of space. However, this does not apply to a small container. Such worms might escape through the drainage holes looking for food or more space. Having them in the kitchen counter where you might have placed your potted herb might not be the best of the experiences. 

Either case that’s a problem that only indoor plant owners might face as, again, space is not an issue in a garden. This, in turn, requires extra attention in not overfeeding worms in a container;

Earthworms require constantly moist soil to live healthily. At the same time, you cannot exaggerate with water otherwise, to avoid drawing they will go to the surface and you might find them on the kitchen counter or on the floor! However, such moist soil might not be suitable for a few herbs such as rosemary thrive more in dry soil, where worms will have a hard time surviving.

Do Earthworms Eat Plant Roots?

At the moment there is no evidence of worms eating plant roots and this is very likely not be the case due to the physical limitations of earthworms.

Earthworms have small mouths without teeth or mandibles. Hence, they cannot bite or chew. They rely on other microorganisms (fungi, actinomycetes, etc…) to break and soften the ‘organic material’ (like dead leaves, and compost) found in soil.

What about the famous Professor Nico study that made the news? Do worms eat plant roots?

Worms were found to eat plant seeds! This should not worry you as worms can only eat extremely small seeds (<2.5mm). Moreover, the experiment was done in a lab where worms were exposed to a lack of other food sources, not typically the case. No, no evidence of them eating plant roots.

Leave EarthWorms in Potted Plants, or Remove?

Hence, in general, earthworms can be good for an indoor plant, however, the attention you should pout to it, in my opinion, does not worth the effort. Indeed, you need to be careful to not overwater the plant, to not overfeed them (otherwise they will become too many for your container), not underfeeding (otherwise might start feeding on the plant).

For such reasons, especially if you are a beginner in managing herbs, I do not suggest using worms. However, if you still want to go ahead, it is possible to grow them and use to the advantage of your herb (and also have a lot of fun!).

If you want the benefits of the worms (almost all of them) without the hassle in maintaiing them you can just use their poop. Wait? Is it available?

Yes, worm feces (also known as worm casting) is the black gold among gardeners and it is a very popular gardening help. I use it for my basil indoor (in a small amount) to promote better growth.

There are many brands in teh market, however, the one I do prefer is the Omri Listed. Quite a good brand as well known from its quality among other friends gardeners that use it. Its price varies with season but a few kgs are quite inexpensive.

Where Can you Find Earthworms for Your Potted Plants?

Hence, you decided to go for earthworms for your indoor pot! But, where to find them? There are two options: Worm hunting or buy them (a bit boring, but quick). I guess you know which one is my favorite.

Worm hunting: I suggest going to a park after a rainy day for some digging. Little advice: in some countries, you might not be able to dig public soil without permission. However, for a few worms should not be a problem and, if you are lucky, you might not even need to dig at all. Use your worst clothes as you might get a bit dirty/wet. 

Once in the hunting field (park) look for spots with birds walking on the ground. If so you are lucky, these are likely to be areas with worms. If the rain was heavy you might also find worms that got lost and are wondering on the nearby road, pathway. I usually go for them as easy to catch

Earthworm on clear sight on a footpath probably close to a green area. This happens after a heavy rain that flooded the worm canals -Photo by Jo Naylor from Flickr

If you are not that lucky you need to get dirty and start digging. You might found that around the web a few suggests using a trowel, but honestly, I do not see the point as you might slice your precious little friend with it. Worms are quite delicate. Once you manage to take them out would place them, with the same soil, in a small plant container that you might need to cover to avoid worm invading your car.

Buy worms: even online is a good option. Yes, they are going to deliver to your door a little plastic box containing dozens or hundreds of such living creatures. But do not worry, for them, earthworms, in the right container, can easily survive a few days of delivery time. Remember to go for “earthworms garden” otherwise you might come up with worms for fishing or for compost purposes. 

The problem with such an approach is that you are forced to buy lots of worms (they are sold in hundreds), way more than what you might need for a couple of indoor herbs. However, the prices are pretty competitive with 200+ worms (way too much than enough for an indoor plant) for around 10 dollars.  

How To Feed Earthworms?

As I said earlier you do not want your worms to get hungry otherwise they will start eating your plant’s roots or they will go to the surface (and out of the pot) looking for food. Hence, what and how should we give them? 

Simple, you need to provide them decaying matter that they typically find in open space. Worms are pretty adaptable and can “eat” a significant variety of food, with few exceptions.

You can add organic matter such old leaves, compost, bark (you can find the latter online). For an even more simple solution “made yourself”, you might use fruit and vegetable scraps (for instance the peel of a fruit, the outer layer of an onion, a rotten apple that you might have forgotten in the counter, tomato, eggshell, bead, teabags, rest of a salad that you did not finish).

Such food should be buried a few centimeters below the soil level and made in small pieces (ideally using a grinder) so that your worms can feed it. Also, the coffee ground can be used, but in moderation, as this will make the soil acidic (and worms, as well as a few plants,  do not thrive in such soils). Avoid meat, any fatty, processed and dairy products.

In my opinion, this is the best way to feed your worms for a simple practical reason: given the limited amount of worms you will have (I am talking about indoor plants, in relatively small pots) you will not need to produce kgs of food scraps daily. So what a normal family (or even one person) can produce is, in general, more than enough. 

As always there is the lazy solution, buy the so-called  “worm food” (just google it when you buy it online) that you might need to mix with the soil of your plant. This looks like regular soil but in reality, is a mixture of grated organic matter coming from different sources (such as cereal), specifically designed for worms.

However, I do not recommend this path as you need to buy kgs of them at once, way too much for a few herbs in indoor containers and more suitable for gardeners with many plants on an outside field.

On a side note, ideally, you should feed your worm with an average daily amount of food equal to half their body weight (less is still ok, but not more). 

I do recommend weighting the worm you put in, so you can have a rough idea of how much food scarp or worm food you need to put. Indeed, you do not want to overfeed them otherwise their population might grow dramatically with the risk that most of them will escape from the container for lack of space.

Related Questions

Do earthworms bite? No, earthworms do not bite, although some other types of worms can.

How long do earthworms live? Depending on the species of earthworms for up to 9 years, although some claimed that can live up to 20 years.

Further Reading

What Fertilizer Should You Use For Your Basil?

Tips to grow massive basil

Best potting soil for your herbs

Thanks to our reader Zaman for his expert contribution on the matter.

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