Though nightcrawlers are arguably the most well-known worms in the United States, they are actually an invasive species native to Western Europe. These earthworms help eliminate live and dead plant matter that accumulates on the soil surface, allowing for more water and fertilizer to penetrate the soil. Like other worms, their tunnels also help aerate the soil. While nightcrawlers are beneficial to lawn health, they deposit cone-shaped waste products called castings that can be a nuisance. Additionally, nightcrawlers are dangerous pests in heavily-wooded areas, as they can eliminate growing shrubs, trees, and other plants.

Known by a wide range of names, red wigglers are some of the most common composting worms. You won’t typically find them in the soil itself. Instead, they thrive in and under manure, compost piles, decomposing vegetation, leaf litter, and other matter. These earthworms break down kitchen scraps and yard waste into nutrient-rich castings and then naturally spread this fertilizer through a compost pile or yard. Because of this, they are the most popular vermicomposters in American gardens. However, they can also pose a risk as they can seriously damage plant roots if not contained.

A commercially-produced worm, blues are rapidly growing in popularity as vermicomposters. Blue worms and red wigglers are similar in many ways. Both live above the topsoil, feeding on organic matter and producing fertilizer-like castings. Both species are roughly the same size and eat the same materials. They differ in their output: blue worms produce their castings far more often than red wigglers, allowing them to more quickly develop your compost. Blues are also far more active than red wigglers, meaning they are more prone to escaping compost pits and spreading from lawn to lawn.

Pot worms are thin, white worms that resemble small earthworms. Like other species, pot worms are composters that break down organic waste. Notably, pot worms reproduce quickly, reaching populations of hundreds of thousands per 10-square-foot area in short order. The presence of pot worms indicates acidic soil, potentially pointing to a nutrient issue. Though pot worms usually do no damage to living plants or other worms, they can sometimes take nutrients away from other creatures in the soil. Because of their immense population size, pot worms do a great job of aerating the soil.

Despite the name, European nightcrawlers have managed to make their way into gardens across the United States. This breed of composting worms is similar to red wigglers but tends to consume much less food. Additionally, European nightcrawlers will burrow into the soil, usually far deeper than other species. In comparison to red wigglers, these nightcrawlers do better in environments with higher carbon levels, meaning they thrive in compost pits with plenty of fibrous materials.

If you kept your eye on news headlines in the last several years, you might’ve heard about an invasive species threatening local plants: the Asian jumping worm. These pests earned their name by being able to leap a foot off the ground, which assists in their rapid spread. After entering America at some point in the 1900s, they quickly became a problematic species. Asian jumping worms consume more leaf litter than other species, harming the local organisms that rely on those nutrients. Since they live in topsoil, they often end up in mulch, potting mixes, and potted plants.

Usually, land flatworms live in the wet leaf litter layer of forests due to their sensitivity to dehydration. However, some species have adapted and managed to spread to other environments, such as the Southeast United States. Land flatworms are the predators of other key species that keep soil—and the plants that rely on it—healthy. Physically removing these resilient pests is difficult, so many gardeners opt for salting the ground, using vinegar or citrus oil, or commercial insecticides.

Areas with hot climates or short winters are prone to a particularly irritating worm: root-knot nematodes. These roundworms infect plant roots with their larvae, causing galls that drain the plant of vital energy and nutrients. If the plant is young enough, root-knot nematodes may kill it entirely. Nematodes are extremely small, and you may not be able to see them with the naked eye, so even identifying them is a problem. Adding composted matter, manure, and grass clippings can keep nematodes at bay, as can adding neem oil to the topsoil.

The Texas blind snake is not a worm, but only the zoologists among us could probably tell from a glance. These snakes look a lot like earthworms, due to their pink color, small size, shiny scales, and habit of burying themselves in loose soil. Gardeners in Texas and the Southwestern United States should welcome the sight of these unique creatures, as they primarily feast on termite and ant larvae. If they become too abundant, removing moist breeding sites is an easy remedy.

The larval stages of various insects often resemble worms and may even feature the word “worm” in their names. Some common examples of these are mealworms, inchworms, and silkworms. Unlike actual worms, these creatures rarely limit their feasting to organic waste or other insects, instead devouring the plants around them. If you see a strange worm in your garden soil that is hard to identify, it could be the larva of some other insect, which is just one more reason to become familiar with which wriggly creatures should and shouldn't be making a home in your soil.