Elodea canadensis (Canadian Waterweed)

Elodea canadensis

Elodea canadensis, also known as Canadian waterweed, pondweed, or American waterweed, is a species of aquatic plant belonging to the family Hydrocharitaceae. It produces white flowers in early summer (May and June) before dying back in late summer or early fall (August or September).

This invasive aquatic plant grows wild in lakes, ponds, rivers and streams of North America and can be identified by the small white flowers that develop on the surface of its leaves and stems when mature. Elodea canadensis grows best in well-maintained freshwater habitats that have plenty of sunlight and nutrients available to them.

Pondweed is one of the aquatic plants you’re most likely to see at your local pond or lake in the spring when it starts to warm up again in the Northern Hemisphere, so it’s a good time to brush up on everything you need to know about Canadian waterweed.

By learning all of the basics about this plant, you can be sure that you’ll be able to enjoy it fully while also preventing any possible issues that might otherwise arise with its presence in your ecosystem.

Origin and description

Elodea canadensis

In water gardens and cool water aquariums, Elodea canadensis, also known as Canadian pondweed, has become a popular perennial plant.

Naturalized in Europe, but native to North America. Anacharis canadensis was the former name for this species. Also called waterweed or anacharis. A small bunch of this plant is sometimes available for aquariums where it provides interesting foliage and is used to oxygenate and clarify water.

However, its closest relative, Egeria densa (Brazilian waterweed marketed under the name anacharis), is more commonly used as a water clarifier. In addition to controlling algae, it keeps waters clear by absorbing nutrients.

A small, drooping shrub with dense, lance-shaped to ovate dark green leaves arranged in whorls of three. The stems are fragile, branching, tangled, and grow to 3.5 inches (10 or 12 inches in the wild).

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The flowers appear in July and September and are apetalous, and greenish-white. It is dioecious, since the flowers of the male and female plants appear on separate plants. Due to the rarity of male flowers, stem fragmentation and not sexual reproduction are more commonly used for propagation.

Normally, pollination occurs by waterborne transfer of pollen from male to female flowers. Turions (buds) are also produced by plants and sink to the ground in the fall, overwinter as dormant buds, and reappear in the spring as new plants. Fish, crabs, insect larvae, and snails benefit from the cover provided by wild colonies.

Elodea canadensis common name

Common names for Elodea canadensis includes American duckweed, Canadian elodea, anacharis, Canadian pond weed, American elodea, Canadian pondweed, American waterweed, Canadian waterweed, elodea, waterweed, oxygen weed, and common waterweed.


A wide range of habitats is suitable for Elodea canadensis, but it prefers quiet ponds, lakes, and slow-moving waters with peat, mud, and silt. Many inland freshwater bodies (ponds, lakes, ditches, irrigation channels) have nutrient-rich or eutrophic water flows and a lot of American duckweed can be found in such places, often associated with organic-rich muds. Only low abundances have been recorded in fast-flowing waters

Elodea canadensis size

Elodea canadensis grows from 12 to 36 inches (30 to 90 cm) wide and 3 inches (7 cm) tall. Water gardens generally have little trouble controlling this plant, but larger water bodies can become overrun by this plant if it spreads rapidly.

Elodea canadensis propagation

As a dioecious plant, Elodea canadensis is less common among males than among females in its natural habitat. Plant reproduction is only vegetative in Europe, involving vegetative fragments and turions (overwintering buds). Male plants have not been recorded since 1903.

Roots can start growing from very small plant fragments at nodes. In general, the growing season lasts from mid-April to mid-October. A plant’s growth slows down in the autumn. A turion is a short stem with densely packed leaves that grows through the summer, breaks off during winter to float around the body of water, then sinks to the bottom over winter where it rests until spring comes.

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Waves, currents, foraging animals, and boat traffic can easily detach overwintering buds and fragments of brittle branches. These fragments form brand-new stands quickly as new roots develop on their nodes. Following its introduction from North America, Elodea canadensis spread rapidly throughout Europe as a result of this method of propagation.

Elodea canadensis care

Elodea canadensis

Light requirements

As a submerged aquatic plant, Elodea canadensis thrives in full sun in water gardens, whether anchored or free-floating.

Water requirement

Clean water with a current of 0 to 1 m/s is preferred by Elodea canadensis. A silty or organic sedimentous substrate is preferred to a sandy substrate in water with an optimal temperature range of 10 to 20°C.

Water retention times and water quality are important factors when considering the habitat preference for Canadian pondweed in lakes. During experiments with high salinity concentrations, Canadian elodea exhibits positive growth. As a result, this species is likely to invade salt marshes and brackish waters if the salt concentration is less than 3 g/l.

Risk of introduction

A particularly invasive species is Elodea canadensis, which has spread outside its natural range due to escapes from garden ponds and the disposal of garden waste near waterways. Originally introduced as aquarium plants, it spread through escape from garden ponds and trade in live aquarium plants.

The populations of Elodea canadensis appear to have been stabilized but are on the decline. Other invasive aquatic plants are replacing it or taking its place in some cases. When people trade this plant, they will almost certainly introduce this species because it is commercially sold as an aquarium or garden plant. There are still new invasions occurring in certain parts of Europe.

There are two countries in Europe that have banned Elodea canadensis: Belgium and Germany. According to the Wildlife Act (England and Wales), Elodea canadensis poses a high risk to the environment, so it is unlikely to be introduced into these regions further.

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Elodea canadensis facts on Invasiveness

Elodea canadensis is a native, submerged, aquatic plant of slower-flowing rivers and natural bodies of water in North America, but can now be found in places outside its native range as an ornamental aquarium species. This plant species has a wide environmental range and grows at an accelerated pace.

It can live in deeper water and has no requirement for the sun in order to reproduce asexually, which means that, when environmental conditions become poor, large quantities of new spores will be released. This guarantees rapid regrowth, even if nutrient availability were to decrease.

Elodea canadensis forms thick, weedy mats which obstruct many recreational activities and make navigation difficult. Moreover, the dense mats outcompete native plants, resulting in a decrease in the biodiversity of a given area, while also increasing the accumulation of organic silts, ensuring that nutrient release further enhances their growth.

A majority of European countries include New Zealand, Australia, Alaska, Cuba, and most of the European countries in which Elodea canadensis occurs. The IUCN Red List classified it as a Least Concern species because of its complicated control and fragmentation. This species is not in need of conservation action.

Environmental Impact

Elodea canadensis

Environmental weeds such as Elodea canadensis are widespread in Victoria, New South Wales, and Tasmania. Freshwater environments with still or slow currents are commonly invaded by this species, which thrives in temperate regions.

Aquatic vegetation assemblages and habitats are modified as a result of infestations of this species. The growth of this species is more vigorous when there is a high level of nutrients in the water.

There are currently the highest numbers of Elodea canadensis in eastern New South Wales and Victoria. Central Coast and Hunter rivers and streams are prone to this weed, which is regarded as an important weed in these regions. Endeavour Hills area, near Melbourne in Victoria, recently experienced a large outbreak of wetlands.

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A number of lakes, ponds, creeks, and rivers in Tasmania have been recorded with Elodea canadensis (including the Derwent, Macquarie, Little Pine Lagoon, Mersey, and Jordan rivers, Arthurs Lake, Brumby’s Creek, and Lake Leake) but the Central Highlands region of this state is where it is most abundant.

Natural Enemies

Snails such as Lymnaea peregra [Radix peregra] and Bithynia spp. are natural herbivores of Elodea canadensis. It can become a biological control agent if natural predators do not control the population of this species.

Yet, Pieczynska observed the effect that the snail Lymnaea stagnalis had on the Canadian pondweed, Elodea canadensis. The results were surprising, for the snail left a sizable effect on the species by shrinking the amount of biomass and significantly damaging it, yet it is able to grow new plants from leftover scraps.

Hygraula nitens, a New Zealand native moth with aquatic larvae, is a study participant that could greatly alter certain types of water weeds when certain aquatic mesocosms are present.

Hygraula nitens’ experimental potentials for the decomposition of Elodea canadensis were positively correlated to that of various non-native plants like Lagarosiphon major, Hydrilla verticillata, Egeria densa, and Ceratophyllum demersum.