World of Worms: Why You Want Them in Your Garden

Earthworms are the Rodney Dangerfield of the garden: to paraphrase the late comedian, they don’t get much respect. 

Unlike pretty pollinators that flit from flower to flower, the underground habitat of these unsung heroes means they are often forgotten, overlooked, or relegated to the pest pile along with slugs, cutworms (which, despite their name, are actually moth larvae), and grass root-eating Japanese beetles. It doesn’t help that worms’ tubelike bodies and slithery nature remind people of snakes (except worms don’t have eyes, noses, or ears), that they flood our sidewalks after a rain — making a walk to the mailbox more like a slippery hopscotch game — or that when we accidentally strike one while digging, we’re likely to find a still-wriggling, dissected segment on our trowel.  

The ick factor is large in that case.

Soil shapeshifters

While that may suggest worms don’t have a lot going for them, the truth is they are essential to a robust garden environment, especially for their burrowing qualities.  

Among earthworms’ biggest benefits to gardeners is this: like little living tillers, they aerate and loosen the soil while they tunnel through it horizontally and vertically, enhancing both soil structure and porosity.

That’s important for a number of reasons.

For one thing, compacted soil — soil that is packed tightly together — has less room for water to seep in and, equally vital, to drain out. When there’s not enough water getting to a plant’s roots (or to a seed or seedling), it can’t absorb the important nutrients that stimulate growth. 

On the other hand, soggy soil can harbor harmful bacteria, mold, and fungus, causing plants to rot. Either way, too much or too little water can be a death sentence for an otherwise healthy garden plant. 

But while worms may be worth hundreds of times their weight in moisture control alone, it’s just one of the advantages of their tunneling action.   

Their underground burrows also allow oxygen to enter the soil and carbon dioxide to be released from it.  Plant roots can’t live without oxygen; it’s essential to energy production and the uptake of water and nutrients. An oxygen-starved plant will be susceptible to dangerous bacteria and root damage, and may die a slow, anaerobic death.

And just through the act of burrowing, worms create more space for plant roots. 

The leave-behinds 

Not only do worms improve plant access to water, air, space, and nutrients, they’re actually pretty good at producing the nutrients healthy gardens require. 

When hungry worms feed on organic matter that plants can’t use directly (including debris such as dead roots and leaves) and on micronutrients in the soil, they naturally ingest soil in the process. Everything gets broken down in their bodies and comes out in better condition than it went in: the “castings,” as worm excrement is called, contain nutrients like nitrogen, potassium, and phosphorus that plants thrive on, available in a form they can use. 

It’s like the circle of life, passing through a very rudimentary digestive system. 

What’s more, beetles that might otherwise gnaw on plant leaves often find worm castings irresistible, choosing to eat them, instead. You may never have imagined that teeny, tiny poop could be nature’s pest control, but there you go. 

Bring on the worms

It’s possible the ground under your feet is teeming with soil-amending worms. If you’re growing flowers or vegetables in containers or raised beds, however — or if your in-ground garden could use some punching up — you may have to make some amendments yourself either in the form of worms or their castings.

Whether you lure worms to your garden with compost or buy them from a worm farmer (and yes, worm farming is a thing), a handful isn’t going to do the trick. It’s generally advised to have at least 1,000 worms in a 4×8 foot raised bed.

Alternatively, you can try container vermicomposting. Also known as worm composting, vermicomposting unleashes the digestive powers of worms, as described above. When you introduce worms into organic matter — think kitchen scraps like banana peels and eggshells, plus paper and debris from your yard — you can create a rich, soil-boosting fertilizer. Worm composting can be done in simple bins or stacking tray systems, but whichever you choose, remember to keep the bins or trays moist and give your worms access to air. Worms will perish if things dry out.

Not a fan of handling live worms? You can buy a bag of castings to give your garden the soil-enriching benefits, with none of the wriggling.

So, the next time you think of worms as little more than fish bait or something to step over, think again. Considering all they do for the soil, dig in and give worms their due.