Learn | Algae and aquatic weed control

Invasive, Non-native, Indigenous Aquatic Plants! What?

The aquatic plants may purify the water column but the topic is far from crystal clear regarding invasive aquatic plants that most don’t want clogging up shorelines, ruining swimming holes, tangling up propellers and tripping water skiers.Eurasian Water Milfoil is a common invasive aquatic plant

About invasive and non-native aquatic plants

We used to think if an aquatic plant was a non-native plant, it was bad, and invasive. Then we used to think if it was native or indigenous it was good and non-invasive. Currently there are some interesting discussions on the topic of which aquatic plants should be removed; which create important habitat; which are native etc. To muddy the waters, try having a discussion about who decides on these definitions based on management regions such as Conservation Authorities or Ministries of Natural Resources, or other agencies that manage such plants!

Our feeling is that we just don’t know the answers to many of these queries. For those who love to categorize, sort, compartmentalize, the discussion on the origin and management of aquatic plants is frustrating. And it may be important for those wanting to remove plants adjacent to the shoreline at the cottage or for those who want to plant aquatics to stabilize other shorelines for example.4 invasive aquatic plants to avoid

Like our economies, we think aquatic plants are becoming more “global” now than at any other time in history. Seed of plants travel on the wind, on the wing, via boats, planes, clothing, you name it. Some are planted on purpose only to become problematic decades down the road. The plants don’t want to be controlled. What would the world look like if we didn’t control plant growth?

To find answers to these questions would make for an interesting PhD study:

  • What is a native plant? Is that the same as indigenous? Who decides?
  • When over time does a plant become native?
  • What is a naturalized plant?
  • What is considered invasive?4 invasive aquatic plants to avoid
  • When is a plant considered invasive?
  • Can a plant be invasive in one region and not in another?
  • Can an indigenous plant be considered invasive?
  • Introduced species?
  • Invasive exotics?
  • Exotic pest plants?
  • Invasive alien species?
  • Noxious weeds?
  • Unwanted vegetation? Are these terms meaning the same thing?

Some invasive aquatic plants to watch for

Here are 8 invasive aquatic plants (pictured on the 2 images above) that you should definitely be cautious about:

  • Flowering Rush, Butomus Umbellatus
  • Purple Loosestrife, Lythrum Salicaria
  • European Frogbit, Hydrocharis Morsus-Ranae
  • Reed Canary Grass, Phalaris Arundinacea
  • Common Reed, Phragmites Australis
  • Eurasian Water Milfoil, Myriophyllum Spicatum
  • Water chesnut, Trapa Natans
  • Knowtweed, Fallopia Japonica

If your are fluent in French, we suggest you consult the French version of this page to read more about these specific plants and their alternatives.

We built our earth pond to create an aquatic habitat for our own pleasure and to share with wildlife. But since the ducks arrived several years ago, we have been battling with unwanted, aggressive, slimy, leach-loving aquatic plants (whose seeds arrived via the duck feces, or so we presume).

Maybe we need to manage the plants as best we can, by cutting them down, collecting their seed pods, removing excess sediment rich with nutrients, blocking the UV rays with pond dye? Or simply re-digging the pond every 9 years or so?

Or maybe we need to understand the plants more? Learn their names, origins, qualities. Appreciate the shade they give to fish, the oxygen they transfer to the water. Perhaps in the planet’s insurmountable intelligence, the plants are proliferating to keep our planet’s oxygen levels balanced because we are polluting our air so badly? Or perhaps the sheer biomass of some aquatics is helping keep our surface waters cooler as our planet warms? Or maybe these plants will become food for millions, if our agribusiness implodes? Who knows?

As pond owners we are always searching for the sweet spot of managing the pond or leaving it alone. It comes down to cost, time, aesthetic, use, and safety. As we learn to understand better the role of aquatic plants and how they are evolving, it will become clearer how the name them and manage them, or not! Good Luck!