Myriophyllum verticillatum

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Myriophyllum verticillatum

Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Saxifragales
Family:	Haloragaceae
Genus:	Myriophyllum
Species:	M. verticillatum
Binomial name
*Myriophyllum verticillatum* L.

The whorled water milfoil, Myriophyllum verticillatum is an invasive aquatic plant.

With the increase in water sports, the spread of many water milfoils (Haloragaceae) has increased over the years. The spread of a milfoil is not only within one area but, sometimes it spread from one area to another many miles away.

To the untrained eye the species of whorled water milfoil can all look similar to other species. Whorled water milfoil (Myriophyllum verticillatum) is a native to much of the United States, Alaska, and the United Kingdom. Whorled water milfoil closely resembles another native milfoil, called northern water milfoil (M. sibiricum)^[1] Whorled water milfoil is also easily confused with four types of invasive milfoils: Eurasian water milfoil (M. spicatum), Variable water-milfoil (M. heterophyllum), Parrot feather (M. aquaticum), and hybrid water milfoil (M. heterophyllum X M. laxum).

Description and identification

The best way to identify whorled water milfoil (M. verticillatum) is by looking at its two different types of leaves. The first type is the submersed leave, which looks feathery and contain about 5 to 14 leaflet pairs per leaf. (Bottom of Photo 3) The whorls along the stem contain about 4 to 5 leaves, which are spaced about 1 cm apart. The other type is known as the emergent leaves. These leaves occur on the emergent spike and are pinnately lobed. From June till September whorled water milfoil produces flowers and fruits above or at the water's surface on erect spikes along the emergent leaves. The emergent leaves are typically two or more times longer than the flowers and fruits.^[2]

Another way to distinguish whorled water milfoil is to look for turions, winter buds that appear toward the end of its growing season. This milfoil is one of a few that produce turions. This characteristic can also rule out other types of water milfoil that lack turions such as Eurasian water milfoil, parrot feather, hybrid water milfoil, and low water milfoil. The turions of this milfoil look like long yellowish-green club-shaped buds with small stiff leaves attached to the submerged stem. In the spring after dormancy the small, thick, dark green turions expand and grow from the stem. As the plant develops roots and continues to grow, the larger green summer leaves are produced at the tip of the plant. Turion leaves can be seen at the base of the plant sometimes into July.^[3] In fall the turions, with some other plant material, often break away from the majority of the rooted plant and float to new areas. Those fragments can be found washing up along shorelines in late fall. The stems of the whorled water milfoil form into mats from branched and unbranched stems that grow to be 20 to 100 inches long.

Habitat

Most whorled water milfoil occurs in semi-shallow ponds, lakes, marshes, ditches and slow running streams of lowland districts ^[4] Milfoil thrives in areas with a light sandy bottom and medium loamy soils. Overall, the plant grows best in still waters with alkaline soils.^[5] Whorled water milfoil is sometimes found with or near other aquatic plants, such as some types of pondweed (Potamogeton strictifolius) and (Potamogeton ogdenii), water star-grass (Heteranthera dubia) and water-marigold (Megalodonta beckii).^[6]

Distribution

Native in North America, Alaska, British Columbia, United Kingdom, Asia, N. Africa, and invasive to Ireland.

Propagation and reproduction

Whorled water-milfoil reproduces by producing turions between September and November each year. These over-wintering turions sink to the bottom of the floor where they remain dormant until February [Caffrey,2006]. These fragments will give rise to numerous small thin roots that bed into soil to start growing in spring. The plants are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by wind.

Control and uses

Whorled water milfoil is a good water oxygenator in small quantities such as fish and frog ponds. It is also ideal in providing protection and respiration for fish spawn ^[5] Management of whorled water milfoil is not exactly know, but natural competition with other invasive aquatic plants has been main control so far.^[7] There are a few management practices that some places are using, but they have not been approved for long-term usage.

References

Caffrey, J.M., 2006. Control of myriophyllum verticilltum L. in Irish canals by turion removal: Hydrobiologia, 2006, 570:211-215.

Chadde, Steve, 2002. A Great Lakes Wetland Flora, 2nd Edition, PocketFlora Press, Laurium, Michigan, pp 229 and 231.

External links

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