By Bev Johnson

Master Gardener

Have you ever heard of plant criminals? How about invasive plants? Same thing but just a different description. An invasive plant is one that is a neat clump one week and the next is 20 feet away trying to strangle the nearest oak tree.

Here are a few plants you NEVER want to put in your flowerbed as they will push everything out of their way on the way to cover the planet.

Old fashioned tiger lilies, or old-fashioned day lilies. They reproduce like rabbits; the lilies carry a disease that can affect your hybrid lilies and the day lilies are just plain ugly. Wildflowers, oxeye daisy, butter and eggs (looks like yellow snapdragons) also called toadflax, Queen Ann’s lace, and orange hawkweed. Common tansy, even the new pretty colored ones, are nearly impossible to get rid of when you want to plant something else. Bell flower is a real stinker. It is a tall plant with blue bell-shaped blooms on a single stalk. The roots are very deep, and it spreads like mad. One gardener thought it was so pretty she transplanted some from an old farmhouse foundation to her flowerbed. She had to dig up every plant and bulb, wash all the soil off them and plant them in a new bed to free her flowers of them.

There are even water plants that can cause problems.  Purple loosestrife or any of its hybrids will fill a slough in only a few years, choking out every other native plant. Flowering rush is nearly as bad in small ponds and sloughs.  This plant can out compete even willows and cattails. Yellow iris is very pretty by a pond but it has the bad habit of wanting all the shoreline.   

Then there are the grasses. Aumur silver grass, miscanthus sacchariflous is horribly invasive. The title Amur in any plant should give you pause. It means it is from an area in the orient with climate similar to ours but harsher apparently as plants with Amur in their name go crazy here.

If you want to see invasiveness in all its glory, just look around Fergus Falls in mid- summer. That pretty bright yellow “ground cover” in the ditches and on the boulevards is birdsfoot trefoil. The Prairie Wetlands is fighting this stinker. It forms dense mats of plants that choke out most other vegetation. This plant was introduced by the Minnesota Highway Department to hold slopes on the interstate. Wonder if creeping Charlie came from the same place.

Bunkey has had personal experience with several other plants that he feels are thugs too. One is purple cone flower. It spreads by seed—all over his flowerbed. Then there is a hybrid bell flower. It looks like a purple drumstick about a foot high. It thrives on Roundup. Lily of the valley and most violets spread like mad too, but they make a nice ground cover in dense shade where Charlie is the only other option. 

The U of M has trees and shrubs on a “do not plant list”. Amur (there’s that name again) maple and Norway maples, Japanese barberry, Siberian peashrub, Russian olive, Exotic honeysuckles, with Latin names of Lonicers tartatica and L. Morrowil, glossy or alder Buckthorn, Siberian elm and black locust, with the exception of the black locust are non-natives and will crowd out native trees and shrubs. Don’t plant them and if you have them, destroy them if you can.

For information on how to destroy these criminals, try the Extension office at 218-998-8760.