Worms and Clay Soil


My garden seems to have become a wasteland for worms. We had plenty several years ago, but for the last 4 years I haven’t seen a single one. The soil has become heavy and wet and we are trying to restore it to better health. I live in East York, and my neighbour has a similar problem.

Is there anything I can do?


Thank you for contacting the Toronto Master Gardeners.

You are not alone in dealing with this problem. We have received a number of inquires from homeowners with a similar problem. The following information is a summary from a few of our archoved posts:

Dealing with compacted soil is a common issue that many gardeners are faced with. It’s most likely that there’s no or very little worms in your compacted clay soil because they’re unable to live or thrive in your soil in its current condition. Simply adding earth worms to your soil is more likely to end up with worms that either leave the soil to find a more suitable environment, or end up dying in the compacted soil unable to find any nutrients from organic material to feed on.

One of the best solutions to your compacted soil would be adding a thick layer of compost or mulch. 2-4 inches (5-10 cm) would be most ideal for your heavily compacted soil.  Even wood chips are a great amendment if you don’t mind waiting for the organic matter to break down. In either case the worms will certainly be attracted when there’s decaying organic matter for them feed off of. Worms are almost everywhere and will appear if you create the right conditions for them. This will in turn improve the underlying soil as well in time.

“Earthworms improve soil quality by increasing air flow, adding nutrients, enhancing the ability of the soil to hold moisture and encouraging proliferation of beneficial bacteria.

The best way to attract earthworms is by amending your soil, as you have started to do.  It is also important to limit activities in the area that would compact the soil (e.g., animals, children running in the area).

Here are links on how to achieve a healthy soil:

Finally, note too that if you do go ahead and purchase worms, non-native worm species can be invasive and harmful to the ecosystem.  For example, they can alter physical and chemical properties of soil, making it difficult for native plant species to grow.  See:

You can add worms to your soil provided you have healthy soil, rich with decaying organic matter. This is a new build and the soil used may be basic black top soil with some compaction underlying, which is not good for soil or worms.

Red wigglers and Nightcrawler varieties are commonly used in composters and may be added to existing healthy soil, but if the soil is well amended with compost, the worms will find their way.

Incorporating a composter in your yard is an excellent way to more quickly introduce worms to your newly amended soil, however.

For further reading, please see below for details on soil amendment:

Amending Clay Soil