Why Do We Have So Many Invasive Plants?

 

The topic of invasive plants is inextricably intertwined with the support for native plants because native plants and their habitats are the most at risk when exotic plants spread. 

Invasive plants are defined as exotic plants that have the ability spread on their own to the point that their spread disrupts native ecosystems. 

Not all exotic plants are invasive; in fact, most of them aren't. My husband helped me put together this overview of terminology.

Know your terms

Exotic plants arrive here initially in one of two ways: someone brought them on purpose (and that’s absolutely true for many of our worst ones) or they arrived accidentally (perhaps as part of cargo such as packing material or stray seeds that hitchhiked). Once they are here, rarely are they identified to be invasive, that determination comes later, even many years later.

Once they arrive, they may live quietly for many years, including being cultivated and passed along. Japanese honeysuckle (Lonicera japonica) was brought here as an ornamental but it is said that it took 80 years before it became apparent that it was spreading enough to be considered invasive. In the last 20 years, many of us watched as ornamental pears such as ‘Bradford’ (Pyrus calleryana) started to spread into natural areas. It is finally designated now as an invasive plant. 

Tree of Heaven

Two more recent pests are Autumn fern (Dryopteris erythrosora) - spreading into streams and natural areas - and Japanese chaff flower (Achyranthes japonica), a pest notably in the Atlanta area but spreading outward.

If invasive plants are so bad, you might wonder why we aren’t doing more about them. How do they spread? 

I like to describe it as the 3 W’s: wind, water, and wildlife. Once the seeds or root fragments arrive in a new spot, it is largely the twin forces of neglect and ignorance that allow them to thrive. Neglect and ignorance are solvable!

I remember being a kid in the 1970’s when the litter campaign was in full force. Litter bags for your car were all the rage – they were created to encourage people NOT to throw their trash out the window. Can you imagine that people thought that was ok? How times have changed.

We need a campaign to say that invasive plants are not ok. It’s not ok to have them and it’s not ok to just let them fill up the roadsides like so much trash. Cities and counties should take responsibility for their roads, learn to recognize these plants (easy with a smartphone or tablet), and have crews remove them just like they remove trash (litter pickup). 

Utility contractors that manage vegetation should be instructed not to just prune invasive trees to protect the lines, they should be instructed to cut them to the ground!

Developers should be required to identify and remove invasive plants on property being developed. Developments near me are leaving invasive plants on property edges, only removing them if they are physically in the way of some section they want to develop.

City, county, and state parks should include in their maintenance plans the detection and removal of invasive plants just like they detect and remove trash. I wrote recently about a park stream restoration project; invasive plants were removed but you could see where they still exist in the unrestored areas.

I hope one day that we look at managing invasive plants the same way we looked at trash in the 1970’s. Humans made this mess and it’s up to us to deal with it in a responsible way.