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Are Roundworms–AKA Nematodes–Sabotaging Your Garden?

Nematodes, sometimes known as roundworms, are teeny-tiny little creatures that live in the soil. While most of them are harmless, a handful of species are nasty parasites that can wreak havoc on your garden. Here’s how to recognize a nematode infestation and wipe them out before it’s too late.

What Are Garden Roundworms? How Can You Recognize Them?

Although they’re called roundworms, nematodes aren’t related to actual worms. The ones found in the garden are microscopic insects, measuring at 1/50 of an inch long! These plant pests aren’t the same kind of parasites that attack the human body, so don’t worry about getting sick from dealing with nematodes in your garden.

Nematodes feed by punching through cells walls, injecting their saliva, and then sucking out the contents. Gross, right? The results aren’t pretty, either. The most common sign of a nematode infestation are root knots or galls. Affected plants might also have stunted, twisted growth or dead spots on their leaves.

Because the above-ground symptoms are similar to many other plant diseases, you may need to dig up the affected plant and examine the roots. The most common variety of harmful nematode causes nodules to form on the roots. These root-knot roundworms are tricky to get rid of, and once you find an affected plant, you should dispose of it in a sealed plastic bag–not your compost heap!

Prevention and Sanitation

One way to ensure that nematodes don’t spread is by making sure you have well-drained soil. Roundworms can quickly move through wet, water-logged soil. Otherwise, they’re pretty much stuck where they hatch–unless you help them move along by tracking tainted soil to other parts of your garden or tossing plants with nematode damage onto your compost pile.

Always clean your garden tools after using them. That’s especially important when you’re dealing with any kind of garden pest or infection. Wash your tools and equipment in a solution of 10% bleach to ensure that you aren’t transferring pests or diseases.

You may have success with marigolds as natural nematode repellents. The flowers produce a sulfurous compound in the soil that’s deadly to roundworms. If you’re struggling with an infestation, planting marigolds around the garden bed may help.


Not all nematodes or roundworms are bad news. Other species are actually beneficial, helping to break down organic matter in the soil and feeding on pests like weevils and grubs. Beneficial nematodes are much bigger–up to a quarter of an inch long–and shouldn’t be confused with their microscopic cousins.

Summer Clayton

Summer Clayton

Summer Clayton has always loved getting her hands dirty. Ever since she was a kid playing in her grandparents’ garden, Summer wanted to learn everything she could about plants. Now she wants to help you grow a bigger, better, greener garden.

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