Avoid Hitchhikers This Summer

By Erika Segerson-Mueller, DNR invasive plant program specialist, Oshkosh
Erika.SegersonMueller@wisconsin.gov or 715-492-0391

Invasive jumping worms have a light-colored clitellum, while most worm species have a raised, pink clitellum. / Photo Credit: Brad Herrick, UW-Madison Arboretum

To reiterate some advice you may have heard long ago from your parents: Don’t give rides to hitchhikers. They may have been thinking about people, but hitchhiking invasive plants, insects and pathogens are also worthy of concern.

As you dream of days spent at the cabin up north, planting your garden or wandering in the woods, here are a few reminders to help you avoid bringing hitchhiking invasives along as you enjoy your spring and summer activities.

1. Know Your Plants

Many plants that we now recognize as invasive started as ornamental garden plants. Aggressive spreaders can easily escape cultivation and spread into nearby landscaping, natural areas or forested land. As you plan your plantings and start your seedlings, keep an eye out for prohibited and restricted invasive plants.

Wisconsin’s nurseries and garden centers are regulated by state agencies and must follow Invasive Species Rule NR40. However, your local plant swaps and garden club sales are not regulated in the same way, so invasive plants can be unwittingly swapped and spread around quickly.

Species may be unknown or have inaccurate descriptions. Since these types of meetups are not regulated, it can be difficult to guarantee what you may be getting. Avoid any plants described as “quick-spreading,” “aggressive” or “easy to grow” unless you can be certain about the species and its possible status as invasive. When possible, opt for native plants or non-native plants that are not aggressive or invasive.

2. Leave Aggressive Species At Home

Avoid creating infestations of invasive plants, such as this huge patch of garlic mustard, on your wooded properties; don’t transport or plant aggressive spreaders as you head up north this summer. / Photo Credit: Steven Katovich, Bugwood.org

If you’ve stopped by a plant swap or sale and are trekking north to your cottage, permanent campsite or summer haunt, don’t bring any aggressive spreading plants with you. Some plants seem great for landscaping, like Bishop’s goutweed, often known as “Snow on the Mountain,” which can fill in landscape gaps quickly. However, invasive plants like goutweed will continue spreading, even where you don’t want them, and can quickly create monocultures in your woods, crowding out native plants or inhibiting tree regeneration.

More remote properties up north may also border local natural areas, which can be vulnerable to invasion by harmful, non-native plants. The northern third of Wisconsin still has many of these natural areas that are not fully infested with invasive plants. Preserve the beauty of your favorite forests, trails and campgrounds by not transplanting your garden plants on your northern properties.

3. Don’t ‘Soil’ Your Property

Another reason not to transplant plants up north is the possibility of spreading hitchhikers. In addition to the plants you intend to move, many hitchhikers can join in the planting, outcompeting the plants you desired and wreaking havoc on your landscaping or forested land.

Seeds from invasive plants such as garlic mustard are small and can easily be carried in the soil, causing new infestations of invasives when plants are replanted or transferred to a new location.

While you’re minding your soil, never dump yard waste into your wooded property, whether from your garden or from another location. While adding “green waste” to a pile or area of your property may seem harmless, invasive plant debris or seeds may be present in the pile and can quickly spread unwanted invasives to your woods.

4. Watch Out For Jumping Worms

Soil that is infested with jumping worms has an appearance and texture similar to coffee grounds.

Soil that is infested with jumping worms has an appearance and texture similar to coffee grounds.

Another nefarious hitchhiker to look out for is the invasive jumping worm. This non-native earthworm was found in Wisconsin in 2013 and can be easily spread when plants are swapped and planted in new locations.

Jumping worms (Amynthas spp.) earned their common name due to their lively behavior. They are very active, can move rapidly side-to-side and may resemble a writhing snake. They have a smooth, light-colored clitellum (the distinctive band near an earthworm’s head), while most worm species have a raised and pink clitellum. Jumping worms can also drop their tails if handled roughly.

One sign that an area may have jumping worms present is a distinctively grainy soil with the appearance of used coffee grounds. Invasive jumping worms grow rapidly and transform soil into loose castings (worm droppings). This is especially harmful in forests and threatens plant establishment, tree root growth and nutrient uptake.

To avoid bringing jumping worms home with you, carefully examine any potted plants and gardening or landscaping materials. If you do come across any writhing, snake-like earthworms on your property, report the sighting by emailing your location, photos, and any other descriptive details to Invasive.Species@wisconsin.gov

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