Spike Watermilfoil Myriophyllum spicatum

Eurasian watermilfoil is a submerged invasive aquatic plant native to Asia, Europe and Africa in the Haloragaceae family. It typically grows in water 3.2 to 13 feet deep, tolerates cold waters and low light conditions, and has spread to nearly every state in the USA and much of Canada. It was likely first brought to North America in ship ballasts or as an ornamental plant for aquariums or water gardens. Once introduced to an aquatic system, it spreads prolifically by stem fragments caused by either natural or mechanical causes. Each plant produces around 100 seeds but the main propagation method for this plant is stem fragments.

This plant interferes with the recreational uses of waterways, obstructs commercial navigation, exacerbates flooding, clogs hydropower turbines and alters ecosystems by crowding out native plants and affecting animal diversity. It will also hybridize with native watermilfoil species making control more difficult.

The stems of this plant can grow up to 20 feet long with feathery whorled leaves around the stem. The plant has separate male and female flowers in summer. A 2-6 inch spike is produced with inconspicuous small reddish or pinkish 4-petaled flowers and is held above the water. until flowering is complete, then becomes parallel with the water.

Insects, Diseases, and Other Plant Problems: No significant problems. On the NC noxious weed list, this species is considered invasive by the NC Invasive Plant Council and in many other states. It is illegal to sell this plant in many states.