Eurasian Watermilfoil

Invasive Eurasian Watermilfoil (Myriophyllum spicatum)

The invasive aquatic plant, Eurasian Watermilfoil, has established itself in parts of the NE Arm of Lake Temagami.

Eurasian Watermilfoil forms dense mats that make it difficult to swim, paddle, and boat. These plants also harm other species by crowding them out! They are disseminated primarily when plant fragments are transported on boat hulls/engines. It is almost impossible to completely eradicate Eurasian Watermilfoil, and in some areas with high levels of infestation, property values have dropped by 15 to 20%.

The following details will be provided below:

  • what you need to know
  • identifying Eurasian Watermilfoil
  • where has Eurasian Watermilfoil been found in the Temagami area, and
  • further reading

Resources on Eurasian Watermilfoil:

What You Need to Know:

  • Learn how to identify invasive Eurasian Watermilfoil and prevent its introduction or spread in Ontario’s waterways.
  • It is illegal to:
    • possess or transport Eurasian Watermilfoil in a provincial park or conservation reserve
    • bring Eurasian watermilfoil into Ontario
    • deposit, release, or propagate Eurasian Watermilfoil (including planting it, or any other actions which may encourage its spread or growth)
    •  buy, sell, lease, or trade Eurasian Watermilfoil in Ontario
  • Never keep or grow Eurasian Watermilfoil in an aquarium, water garden, or for any other purpose.
  • Always clean, drain, and dry your watercraft before transporting to another waterbody.
  • As of January 1, 2022, boaters must open or remove boat drain plugs and other devices to allow water to drain. They must also take reasonable measures to remove plants, animals, and algae from their watercraft, watercraft equipment, and boat trailers before transporting them overland.
  • Boaters must ensure watercraft, watercraft equipment, and boat trailers do not have aquatic plants, animals, or algae attached to them before arriving at a launch site or placing the watercraft into any waterbody.

Source: Ontario.ca website

Identifying Eurasian Watermilfoil (Myriophyllum spicatum):

Source: USGS, 2018 (via Wikimedia Commons)

There are many types of watermilfoils. The concern is with Eurasian Watermilfoil, which has these features:

  1. Eurasian Watermilfoil has more than 12 leaflet pairs per stem. Other species have 5 to 10 pairs.
  2. When Eurasian Watermilfoil is pulled from the water, the leaflets hang limply. When Northern Watermilfoil is out of the water, the leaflets are rigid.
  3. Eurasian Watermilfoil has a pale or pinkish stem. Other species have a pale, whitish-green stem.
  4. Eurasian Watermilfoil tends to branch near the surface.
  5. During July and August, reddish flowers form on the surface.

Is It Eurasian Watermilfoil? (illustration by Tansy Hylands)

Further resources for Identifying invasive and native watermilfoils:

Where has Eurasian Watermilfoil Been Found in the Temagami Area?

As of January 2026, Eurasian Watermilfoil has been identified in the NE Arm near the town of Temagami.

To see the most up-to-date information for Temagami, go to the invasive Eurasian Watermilfoil (Myriophyllum spicatum) map at EDDMapS and zoom into Lake Temagami.

As of winter 2026, EDDMapS lists four locations:

  1. Town docks
  2. double docks at Finlayson Point Provincial Park
  3. docks near the beaches at the park
  4. The fourth location is for the park in general, as the details indicate it is at the park headquarters on the mainland rather than on water.

The freely available iNaturalist app (https://inaturalist.ca) may be used to identify invasive Eurasian Watermilfoil (Myriophyllum spicatum). EDDMapS utilizes both data from iNaturalist and from users.  EDDMapS has an app called EDDMapS Pro that can be used without an internet connection.

Searching iNaturalist for Watermilfoil instead of Eurasian Watermilfoil provides the four locations listed above, along with these additional locations:

  1. North Tetapaga River: possible Northern Watermilfoil
  2. Small Lake North of Camp Wanapitei: possible Alternate Watermilfoil
  3. Mainland West of the North Arm: possible Alternate Watermilfoil
  4. North Arm of Temagami: possible Northern Watermilfoil or Alternate Watermilfoil

Eurasian watermilfoil may also be present at Boatline Bay and at the Lake Temagami Access Road landing.

The “Natural Resources and Environment” committee of the TLA is researching options to survey portions of the Lake for this invasive aquatic plant.

Please watch for possible Eurasian Watermilfoil patches, and report any sightings to the TLA. First check the “Invasive Species” section on the TLA website, and if the infestation has not yet been reported, e-mail the location (with photos) to temagami-invasives@lists.conic.net.