We are no strangers to invasive species at Naturedigger. Many of our apps highlight invasive plants and/or animals and raise awareness about the damage they can cause if not kept in check. Since this week (2/25 through 3/3) is officially National Invasive Species Week, We are highlighting one of the world's top 100 most invasive species, knotweed. First, here is some basic information about invasive species.
How does an invasive species get transported from its natural environment to one that allows it to thrive and take over?
Typically, plants and animals are brought to the U.S. and Canada accidentally and undetected, but not always.
• Can arrive either with nursery stock unintentionally or as ornamentals (on purpose) which are purchased and prized by gardeners (i.e. giant hogweed)
Aquatic plants and animals:
• Often arrive in the ballast water of large container ships entering our waterways (think zebra mussels). Once they release their water, everything they picked up in their home port is now quite happy living in ours.
• Fishermen often transport fish and plants from waterbody to waterbody unknowingly, so remember to Clean, Drain and Dry your boat and fishing gear before launching into a new waterbody.
• Careless aquarists also help spread aquatic invasive species such as fish, snails and aquatic plants because they often release them into local waterbodies once they are no longer interested in keeping them. This is a huge problem and species such as elodea and goldfish are becoming a huge issue for freshwater ponds and lakes. Always contact your local pet store to drop off any unwanted plants or animals or list them for sale or for free.
Why do so many foreign species take over?
Occasionally when released to a new environment, a plant or animal may either die off quickly due too poor conditions, lack of food, lack of mates or something they require but can't obtain in their new environment. However, quite often they spread or grow out of control primarily due to the absence of whatever kept them in check in their home range. This could include bugs, diseases, climate, soil type and myriad of other things that allow them to grow normally and not expand beyond their normal range.
A perfect example of a plant that has gone unchecked and is exploding across the country is knotweed. This seemingly unstoppable plant blocks wildlife corridors, causes flooding as well as expensive property damage. It can change water chemistry and become a monoculture in areas of sensitive habitat, like river banks. Japanese knotweed is the most commonly recognized of the knotweed species, however, there are four separate species, which includes a hybrid. All knotweed species are aggressive and costly both to homeowners and to open space, wildlife and public park managers.
Below are images of all four species. Check out our Nature Education section on this site for more identification help and download our iOS app, Knotweed! to learn to identify all four species using our Quick ID slides. Also, take a look at the management plan in the More... menu of the app in the event you encounter it on your own property. To ensure you never bring knotweed into your life, always be aware of where your topsoil and mulch come from if you are doing a landscaping project. If you employ a lawn maintenance company, ask them if they are able to identify knotweed before they park on your property or unload any equipment. And NEVER back your car or truck into an area with knotweed, since just a single node from the stem can get stuck in your tire tread and drop onto your lawn starting a new infestations.
Since knotweed will find a way to break apart roads and in some cases the foundation of your home (when growing nearby), it is very important to learn to identify it quickly and take care of it before it becomes a major issue. See structural damage photos below as inspiration to learn to identify knotweed in the early stages before they become a headache and a ten year long management project.
Knotweed structural damage