Cultivating a healthy garden is an enlightening and fulfilling experience, but as veteran gardeners know, such an achievement requires not only aesthetic creativity but also a connection to and an understanding of the soil in which plants are grown. There are many techniques that gardeners employ to create ideal soil conditions, such as gentle tilling and scheduled watering for aeration and moisture. However, there is a biotic community, which is less commonly considered, that does a lot of the soil-conditioning work for us. Made up of many different kinds of organisms, this underground society supplements the gardener’s efforts and ultimately mediates a soil’s ability to provide a desirable plant habitat. One of these key players is the earthworm.

Earthworms contribute significantly to soil health as they burrow through the soil and feed on organic matter and microorganisms. There are thousands of earthworm species worldwide. These species are placed into one of three groups based on their feeding and burrowing habits. Each group contributes to soil health in different ways, but they all have a couple of things in common.

As earthworms feed, smaller fragments of organic matter are mineralized by microorganisms inside their gut and, upon excretion, become readily available to plants. Earthworms continually excrete these castings throughout the soil profile. There, the castings rapidly stabilize and become resistant to chemical and physical degradation. This benefits overall soil structure by helping to prevent compaction. Castings also act as storage units for nutrients such as carbon and nitrogen.

Furthermore, as earthworms burrow, they secrete mucus from their bodies to aid in tunneling activity. A mucus-lined burrow typically contains a higher nutrient content than the surrounding soil.

Give them what they need

If your soil doesn’t seem to contain many earthworms, there are ways to encourage activity. First, you need to provide a steady supply of organic matter like grass clippings, manure, leaves, or kitchen compost. Second, when starting a garden, take care to turn the soil; earthworms can move more easily through loose soil than highly compacted soil.

Third, try to keep the moisture level of your soil fairly even. Just like the plants in your garden, earthworms are moisture sensitive. They will typically mate and lay eggs during times when soil moisture is relatively high. Oversaturation or the drying out of soil can cause earthworms to retreat deep into the soil profile and enter into a resting phase. In the case of excessive moisture due to a heavy downpour, however, earthworms often come up to the surface for oxygen since their burrows become flooded with water.

It is also important to note that earthworms can be sensitive to chemical changes in the soil, particularly those caused by the addition of pesticides or chemical fertilizers to the garden. Since overapplication of these products can kill earthworms, such chemicals should be used as little as possible and applied with extreme caution when necessary.