By Bev Johnson

Master Gardener

Gardeners, are we really being invaded by aliens? Alien plants, and animals that is.  Well, probably not. At least according to Felicia Parsons, a horticulturist. She says about 95 percent of the animal species currently in South America are believed to have evolved from animals that migrated from North America millennia ago. Those that came this way didn’t fare as well. Cold weather is not all bad. It does keep the riffraff out.

Did you know for instance, that earthworms are probably not a native species? They most likely came with people bringing their favorite plants and seeds from their native countries to make their new home more like their old home. Dandelions for instance, were imported because the leaves were considered a delicacy. Now back to the worms. They have been implicated in the reduction of northern hardwood forests due to their destruction of the leaf duff that results in bare earth that tree seedlings have a difficult time germinating in. Gardeners encourage worms as they add to the tilth and fertility of the soil. Night crawlers on the other hand make for nasty lumps in the lawn.

Scientists sitting in their offices assumed that each plant or animal filled a particular “niche” and if a foreign plant or animal was introduced, it would crowd out the native and eventually make it extinct. The guys out in the field and even amateur gardeners said, “hey, hold on there.” They found that newcomers seldom ever totally displace the natives. As Felicia Parsons says, “they play pretty well together.” Even if the newcomer is a bully, like the ox eye daisy, a “ditch plant.” It will fill up every corner of the flowerbed, then head for the neighbor’s garden. Your Glorisosa daisy will hold its own. Ox eye daisy can be a bear to eradicate in the home garden so never, never plant ditch flowers in a mixed flowerbed. Give them a field of their own.

There are some thugs that the state of Minnesota will insist you kill off.  Here are a few plants. Bull, musk, Canada and plumeless thistle, leafy spurge, hemp, field bindweed, purple loosestrife, garlic mustard, and poison ivy. There are also trees and shrubs on that list.

There is also an international list of thugs that impact us, a few of which may surprise you. They are the domestic cat, the fungus that causes chestnut blight, zebra mussels, gypsy moth, purple loostrife, the house mouse, the fungus that causes Dutch elm disease, and the European starling. There are more every day it seems.  These have been implicated in the extinction of indigenous species in the ecosystems they have invaded.

Gardeners have discovered that any plant, shrub or tree imported from China, can become a problem. Any plant that has amur as part of its name seems to really love this part of the country and does very well.  That being said, habitat destruction and species extinction because of introduced species are far less frequent than we once thought according to Professor Parsons.

As gardeners, we like a variety of plants in our gardens and will jump at a new introduction. A word to the wise, never plant the newest introduction. Give it at least three years to see if it will thrive here or become a pest. Remember Endless Summer Hydrangea? It was better named endless bummer in this area. It just didn’t do well and needed acid added to the soil each year to stay blue, thus damaging the soil. 

Some new cultivars become invasive, don’t winter well, get ugly as they age or just don’t prosper.  The moral of this article is, don’t believe every new study or new blurb about a new introduction and never plant ditch plants in your flowerbeds.