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It's Tempting, But Please Don't

By: Sandra Nelson

purple loosestrife

Purple loosestrife has been a hot topic around here lately…


  stumpEarlier this spring we had a tree removed from our front yard, leaving an unsightly bare spot right next to the entrance of our house.  It hit you full-on, whether you were approaching the house from the street or the driveway so it desperately needed some green relief. Throwing out some ideas, one of my daughters came up with the idea “to plant some of that purple stuff we used to have in our yards. That was always pretty.”

She was right about the “purple stuff.” Forty years ago, purple loosestrife was one of my absolute favorite plants. I planted it at every house we lived in –  and there were many  –  so that those lofty, purple spikes could be the show stoppers of my summer gardens. They were not only beautiful, but they were reliable for a novice gardener. They unfailingly returned year after year and, for the most part, remained where they belonged… or so I thought. I didn’t realize that the seeds were being carried off to new homes by the winds and by birds. field of purple loosetrife Once established in their new environments, the non-natives would quickly overrun native species necessary to maintain a healthy ecosystem. Without the familiar vegetation that they co-evolved with, birds and other wildlife eventually lose their sources of food, shelter and nesting materials. Just like the native plants, the native wildlife first suffer and  then begin to disappear. 

Even though we have seen the obvious local effects of invasive species, researchers are just now beginning to discover surprising, long-term consequences.  In woodland areas, for instance, tree-climbing invasives, think Kudzu, are reducing the tree canopy and are toppling mature trees. A    kudzureduced canopy increases air and ground temperatures by 11 to 19 degrees F. In an urban setting, a reduced canopy or loss of trees themselves has a direct link to higher asthma levels and debilitating heat islands. As an added bonus, areas that are deforested can be easily overtaken by invasive shrubs such as Japanese honeysuckle, which then prevent regrowth of desirable young trees.

Other studies have tied invasive plant species to degraded water quality from runoff –  invasives tend to have shallow root systems as compared to natives, allowing soil to contaminate water systems. This becomes particularly dangerous in areas with high chemical use.invasive by water

Agricultural land suffers when invasive plant species begin taking over areas and leaching both moisture and nutrients from the soil. Grazing animals can be deprived of food sources since they will often forage for familiar native plants. As the invasives crowd out the natives, cows there is less food available. Farmers and ranchers then need to supplement the animals’ diets, which of course raises prices for consumers.  Human health is also directly impacted by the increasing number of invasive species. One Asian study found that an influx of mosquitoes accompanied the spread of several plants introduced   from other regions. Here in the United States, several species of ticks are accompanying the movement of plants. Other invasives, like the now common wild parsnips, cause burns and blisters on bare skin when simply brushed against.

Over the past few years, purple loosestrife has become the poster child for invasive species. It is so aggressive and harmful to the environment that almost every state in the union (except Florida, Alaska and Hawaii) have declared that it is an invasive plant. Here in Missouri, it is illegal for retailers to sell Lythrum salicaria. Unfortunately, since it isn’t illegal to sell it in all states, seeds and plants can be easily purchased from Amazon and a slew of other online retailers. (As an aside, for those of us who still secretly love purple loosestrife, hybrid, seedless varieties like Morden’s Gleam however, are permitted and are beginning to be seen in some retailers.)  

Although it is one of the most beloved problem plants, purple loosestrife is definitely not the only species of which we need to be aware. In Missouri, barberry and burning bush are on the list, as are bradford pearNorway Maples and Bradford Pear trees. Each state produces a listing of species specific to the area that are considered invasive, so it is easy to check whether a new or existing plant threatens the local ecosystem.

Knowing what I know about purple loosestrife, I can’t introduce that into my garden and risk introducing it to our surrounding ecosystem. Instead, I’ll need to do some research to see what I can plant instead. (We don’t have Morden’s Gleam here.)  Join me next week as I share what I’ve learned  –  and provide a list of native alternatives to some popular, but problematic plants.