Would you be surprised to learn that earthworms are an invasives species in Minnesota? I learned the nasty truth about earthworms in 2009 during a Master Naturalist course. Earthworms may help aerate the soil in my vegetable garden but are extremely detrimental in my woodland. 


Earthworms could be solely responsible for the proliferation of garlic mustard (Alliaria petiolata – a prohibited noxious weed in many states) and other invasive plant species according to Larry Gillette, Senior Wildlife Manager at Three Rivers Park District. Earthworms expose bare ground when they eat away the duff layer. Duff is the accumulation of leaves and dead plant material on the forest floor. Many understory trees, including sugar maples, struggle to survive and thrive without a duff layer.  Historically, woodland areas had 4 to 6 inches of duff layer to: 


duff layer missing

Garlic mustard grows freely where duff layer is lacking

~ protect woodland plant roots
~ retain soil moisture
~ add nutrients to the soil
~ inhibit germination of alien seeds 



If fighting the buckthorn battle and controlling other non-native invasive plants isn’t enough, now we have to dig up millions of earthworms? Not likely, so consider these alternatives:

Add mulch or woodchips where bare soil is exposed.
Remember all that buckthorn you cut down? Mulch or chip that buckthorn back into your woodland. Do-it-yourself folks can rent a chipping machine or hire a professional to do the work. Heavy equipment can tear up soil and damage plants so keep equipment at the woodland edge or on a firm path or frozen ground. Avoid placing woodchips near wetland areas where the leached nutrients can result in increased algae growth.  

Use leaves or compost to mulch bare ground.
Blow or rake your leaves into wooded areas (but away from wetlands). Use an old sheet to carry leaves farther into the woods. I shred leaves through a brush hopper on a small chipper which makes great mulch material. Compost also makes a great ground cover. 

Leave dead trunks and large branches flat on the ground.
Trunks and branches should have soil contact and be placed perpendicular to a slope to slow the flow of water and prevent erosion. Logs and branch sections are useful in defining trails in your woods. 

Time to end this blog segment – I’m worn out from all the ground we’ve covered. 

Landscape Restoration, Inc.







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