Submersed Plants

 
Species: Myriophyllum sibiricum Komarov (synonym Myriophyllum exalbescens Fern.), northern milfoil, northern water-milfoil
Family: Haloragaceae

Northern milfoil is a native plant which commonly grows in lakes, rivers, and ponds throughout Washington. Like the other aquatic milfoils, it has feather-like leaves below water, and flowers and tiny leaves arranged on emergent stalks. Northern milfoil can often resemble and be confused with Eurasian milfoil, sometimes to the point where chemical analysis is required to distinguish them. In general, however, northern milfoil tends to be a more robust plant and has fewer and more widely spaced leaflets pairs than Eurasian milfoil.

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Leaf: Two types. Feather-like olive-green submersed leaves are arranged in whorls of 3-4 with fewer than 14 leaflet pairs per leaf, each leaf to 4 cm long. The leaves usually do not collapse when removed from the water. The leaflet pairs at the base of the leaf are much longer than those at the tip giving the leaf a lance shape. Emergent leaves are located beneath the flowers on the flower stalk and are tiny (1-3 mm long). They are smooth edged to coarsely toothed and are shorter than the flowers.

Stem: The up to 3 m long stem is often reddish when fresh and usually is visible through the widely spaced leaves. Surface branching is sparse in water more than 1 m deep. 

Flower: Tiny flowers occur on often red or reddish-purple emergent spikes up to 15 cm long. Female flowers lack petals; male flowers have 4 petals and 8 anthers.

Fruit: Nutlike, up to 3 mm in diameter, separating into 4 chambers, 1 seed per chamber.

Root: Fibrous, will sprout from fragments.

Propagation: From winter buds, plant fragments, and seeds.

Importance of plant: Provides cover for fish and invertebrates. Supports insects and other small animals and waterfowl occasionally eat the fruit and foliage.

Distribution: Northern half of North America, Europe, and western Asia. 

Habitat: Lakes, ponds, and rivers. Tolerant of nutrient-rich, alkaline, and brackish waters.  

May be confused with: Eurasian milfoil (Myriophyllum spicatum), which generally has thinner stems, more leaflets (usually more than 14 pairs per leaf), and leaflets of more uniform size producing a squarish leaf tip shape rather than a pointed leaf tip. Also easily confused with other milfoils when flower spikes are absent. Often chemical or DNA analysis is required to be certain of identification.

Photographs: Closeup of Myriophyllum sibiricum leaflets. Note also the winter buds (turions) forming on the top right plant.

Line Drawings: Myriophyllum sibiricum


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