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Secret garden helpers: nematodes and worms


Follow these basic steps to protect your soil's health

by: COURTESY PHOTO: DEAN MOBERG - Troop 40643 Girl Scouts Evie Bustamante and Natalie McIntyre learn about worm bins at a recent sustainability fair.With all this sunshine, it has been a great time for mom and dad to have their little helpers out in the garden. Kids aren’t the only garden helpers that can help plants thrive, though.

The soil is full of amazing creatures that do more than just fascinate little ones. Here’s a rundown of some of the many ways insects improve soil health — and

a few tips for helping them get the job done.

n Nematodes: There has been a lot of interest in nematodes in the gardening community in the last several years, as well as a lot of confusion. Largely, the confusion stems from the fact that these very tiny non-segmented worms can be helpful, harmful or some combination of both depending on the nematode.

To start with, not all nematodes have the same diet. Some consume bacteria in the soil, while other feast on fungus and still others focus on eating other nematodes and protozoa. Then there are the omnivores — like us, they eat a bit of everything.

The good news is that, whatever their diet, most nematodes are not parasitic. Many help control plant diseases by grazing on bacteria and fungi. They also move nutrients through the soil, making them more available to plants. Nematodes also help out in the garden by providing a source of food for larger soil organisms and moving bacteria and fungus around within the soil.

What works? You can help support the health of the nematodes living in your garden by following the basic steps for protecting soil health. Soil moisture is particularly important, as is preventing erosion — keeping your garden covered between crops is a useful approach to managing soil moisture as well as helping to fuel the soil food web year round. Some gardeners go so far as to add new or additional nematodes as a type of inoculant to their soils each year. If, on the other hand, you find that a particularly nasty nematode is causing havoc in your garden, other species of bacteria and fungus may be useful in controlling it. You can learn more about these approaches at most local organic garden centers.

n Worms: Oh, the lowly earthworm, superstar of the soil health world! There probably isn’t a gardener in Washington County who couldn’t exclaim how helpful worms are to protecting soil health. Most people have only seen earthworms when they rise to the surface of the soil after a drenching rain, but they can be found working at all levels of the soil structure.

What many may not know is that the earthworm, for all its hardworking contributions to soil health, isn’t originally from around here. Earthworms were introduced to the United States by European settlers, who brought barrels of soil along for the ride in the holds of their ships to provide ballast for the journey to the New World. When they arrived, the soil was dumped, earthworms and all, to make room for all manner of resources and goods being shipped home.

Unlike many introduced species that end up wreaking havoc on local ecosystems, however, the earthworm has by and large been a beneficial addition. Earthworms are quite a bit bigger than nematodes and create much larger pore spaces in the soil, allowing better infiltration of water and nutrients. These tunnels also make it easier for plant roots to penetrate the soil.

As the earthworm pushes its way through the soil, creating the tunnels, it excretes a substance that essentially glues soil particles together, helping stabilize the soil. Earthworms are also major decomposers of organic material, breaking it down and releasing it in their castings in a form that is more useful for plants.

Families and individuals can enjoy raising worms and composting household waste by creating an easy-to-care-for worm bin right at home. Metro offers a great guide to building a home worm bin. Before starting, consider how much fruit and vegetable waste will be generated each week. For each pound of weekly waste the worms recycle, there needs to be about one square foot of space to allow for good circulation of air. Buy some worms to get started and find a nice temperate spot to keep the bin at 55 to 80 degrees Fahrenheit.

Contact the Tualatin Soil and Water Conservation District office for sample designs or by emailing Jen at This email address is being protected from spambots. You need JavaScript enabled to view it..

Learning more

Families can also explore soil with a fun and simple experiment that requires only a tool to dig with, a bucket and a magnifying glass. Place a bucket filled with dirt in a hole, then wait a few days for soil critters to show up. This is a great activity for talking about the soil food web, which helps kids understand how soil is made and kept healthy over time.

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For those interested in learning more this summer about soil health, Rural Living Field Day offers an opportunity to explore many different topics related to managing small farms, gardens and acreages in many areas. Hosted by the SWCDs from Washington, Multnomah and Columbia counties, the day is filled with sessions on topics like building soil health, dealing with weeds, maintaining home orchards, marketing your small farm products and more. Visit swcd.net or contact Jen at This email address is being protected from spambots. You need JavaScript enabled to view it. to register or for more information.