Open the Advanced Search

Whorled Water Milfoil

Myriophyllum verticillatum

Please keep in mind that it is illegal to uproot a plant without the landowner's consent and care should be taken at all times not to damage wild plants. Wild plants should never be picked for pleasure and some plants are protected by law.
For more information please download the BSBI Code of Conduct PDF document.


Plant Profile

Flowering Months:
Haloragaceae (Water Milfoil)
Life Cycle:
Maximum Size:
2 metres long
Ditches, ponds, water, wetland.

Green, 4 petals
The flowers are in whorls above the surface of the water. Wind pollinated.
The fruit is a nut.
The pinnate leaves are usually in whorls of 5 and they have feathery, leaf-like bracts at the base. The leaflets are thread-like. There are between 5 and 14 leaflets per leaf. The leaves are slightly longer than those of the similar looking Spiked Water Milfoil (Myriophyllum spicatum). Whorled Water Milfoil is a perennial.
Other Names:
Myriad Leaf, Whorl-leaf Water Milfoil.
Frequency (UK):

Similar Species

Other Information


Myriophyllum verticillatum, commonly known as whorl-leaf watermilfoil or whorled water-milfoil [1], is a native to much of North America, North Africa, and Eurasia. It is an aquatic herb of the Haloragaceae family, with winter buds that are club-shaped at the ends of non-flowering branches and generally found in fall. The leaf has three or more lobes distributed along a central axis and is once pinnately divided, with the segments being very narrow. Additionally, it is often monoecious with either bisexual flowers or male and female flowers separately. Myriophyllum verticillatum is often found in shallow wetlands, rivers, and ponds.


Whorled Water Milfoil: Understanding this Invasive Aquatic Plant

Whorled water milfoil, also known as Myriophyllum verticillatum, is a highly invasive aquatic plant that has taken over many freshwater ecosystems in North America. This species has the ability to grow and spread quickly, and outcompete native aquatic plants, resulting in significant ecological, economic and recreational impacts.


Whorled water milfoil has feather-like leaves that grow in whorls of four to eight around its stem. The leaves are usually about 2-4 cm long, and the stems of this plant can grow up to 2 meters in length. Whorled water milfoil is usually found floating on the surface of the water, but it can also be rooted in the bottom sediment of a lake, pond or river.


Whorled water milfoil is native to Europe, Asia, and Africa and was introduced to North America in the mid-20th century. This species can survive in a variety of aquatic environments, including still or slow-moving water bodies, and can tolerate a range of water temperatures, salinity levels and light intensities.


The rapid spread of whorled water milfoil has resulted in the decline of native aquatic plants in many freshwater ecosystems. This plant species can form dense mats on the surface of the water, which reduces the amount of light that penetrates the water column, and affects the growth of other aquatic plants. Additionally, the thick mats of whorled water milfoil can alter the water quality by altering water temperature, dissolved oxygen levels and nutrient cycling, leading to further impacts on the aquatic ecosystem.

Moreover, the dense growth of this species can cause problems for recreational activities, such as boating, fishing, and swimming. The tangled mass of stems and leaves can create navigation hazards and interfere with water sport activities.


There are several methods for managing whorled water milfoil, including physical removal, biological control, and chemical control. However, it's important to note that the most effective management strategies are those that are integrated and take into account the local ecological conditions, as well as the specific goals of the management effort.


Preventing the introduction and spread of whorled water milfoil is crucial in maintaining healthy freshwater ecosystems. The most effective way to prevent the spread of this species is to avoid transporting it from one water body to another. Boaters, anglers, and other recreational users should clean their equipment and drain all water before leaving a lake or river to prevent the transfer of plant fragments to new waterways.

In addition, it's important to avoid purchasing and planting whorled water milfoil or any other non-native aquatic plant species in your pond or aquarium. Instead, use native plants that are adapted to the local conditions and will not harm the environment.


Educating the public about the dangers of whorled water milfoil is critical to the success of any management effort. The general public can play a significant role in preventing the spread of this species by following simple practices such as cleaning boats and equipment before using them in another water body. Moreover, public awareness campaigns can help to raise awareness of the ecological, economic, and recreational impacts of this invasive plant.


Continued research into the ecology and management of whorled water milfoil is important to better understand its impacts and to develop more effective strategies for controlling this invasive species. Researchers are studying the biology of whorled water milfoil, including its reproductive strategies, growth patterns, and tolerance to different environmental conditions. This research can help to improve our understanding of how this species is able to invade and impact aquatic ecosystems, and inform the development of more effective management strategies.

In addition, researchers are also exploring the use of native predators, such as certain species of fish and insects, as a method of biological control. This approach has the potential to reduce the population of whorled water milfoil without causing harm to other aquatic species or affecting water quality. However, further research is needed to determine the effectiveness of this approach and to minimize the risks of unintended consequences.


Partnerships between government agencies, non-profit organizations, and local communities are critical to the success of any management effort. These partnerships can bring together resources, expertise, and funding to support effective control and management of whorled water milfoil. In addition, local communities can play an important role in monitoring and reporting new infestations, as well as participating in control and management efforts.

In conclusion, the continued growth and spread of whorled water milfoil pose a threat to freshwater ecosystems, recreational activities, and the economy. A comprehensive approach, including research, education, partnerships, and management, is needed to effectively control and minimize the impact of this invasive species. By working together, we can help to protect our freshwater resources and maintain healthy aquatic ecosystems for future generations.

Distribution Map

Reproduced by kind permission of the BSBI.

Click to open an Interactive Map