Controlling Invasive Aquatic Plants along the Coastal Plain
Thorough guidelines for controlling each of the following species can be found in Cherri Smith's manual distributed by N.C. Department of Transportation.
Please follow this link to get this FREE manual:
http://www.ncdot.org/doh/preconstruct/pe/neu/NEUProcedures/NCDOT_Invasive_Exotic_Plants.pdf
Alternanthera philoxeroides (Alligatorweed)
Photo credits: Flower: Gary Buckingham, USDA Agricultural Research Service, Bugwood.org; Mat: James H. Miller, USDA Forest Service, Bugwood.org
This weed has spread along the Atlantic and Pacific coasts of the United States. It grows in both aquatic and wetland ecosystems. Through stem fragments, the plant can disperse through waterways and reproduce itself from shooting roots out of its stems.
The plant forms vine-like mats in waterways and in wetlands. The vines can grow out 3'. Aquatic forms of the plant have hollow stems; terrestrial forms have denser stems. Oblong leaves grow oppositely along the stems and are up to 4" long. In summer, small, white flowers grow at the point where the leaves meet the stem; flowers are reminiscent of clover.
Egeria densa (Brazilian Waterweed)
Photo credits (left to right): Robert Vidéki, Doronicum, Bugwood.org; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Introduced as an aquarium plant during the 1900s (and still on sale today!), Brazilian waterweed has since choked up the waterways across the United States. It forms dense mats which take over native plant habitat and degrade waterfowl and fish habitat. It reproduces only though stem fragments.
This aquatic plant is submerged but its flowers will emerge during the early summer. The flowers are small and white with only 3 petals. Its leaves are small (1" long) and serrated. They whorl around the stem in groups of 3 - 6. The leaves look similar to hydrilla (see below) but the underside of the midrib is smooth - not spiney.
This aquatic plant is submerged but its flowers will emerge during the early summer. The flowers are small and white with only 3 petals. Its leaves are small (1" long) and serrated. They whorl around the stem in groups of 3 - 6. The leaves look similar to hydrilla (see below) but the underside of the midrib is smooth - not spiney.
Hydrilla verticillata (Hydrilla)
Photo credit: Chris Evans, River to River CWMA, Bugwood.org
This weed is found mostly in waterways in the Piedmont region of North Carolina. It reproduces itself usually by stem and root fragments which disperse through the water. It grows vigorously and forms mats along the surface. It degrades water and blocks waterways.
It is an aquatic plant, found both submersed (as a vine) and on the surface (as a mat). It roots to the bottom and is free floating. Stems can reach as long as 25'. Serrated leaves (0.2 - 0.8" long) grow in whorls of 3 to 8, along the stem. Along the reddish midrib of the leaf, on the underside, there are small spines.
It is an aquatic plant, found both submersed (as a vine) and on the surface (as a mat). It roots to the bottom and is free floating. Stems can reach as long as 25'. Serrated leaves (0.2 - 0.8" long) grow in whorls of 3 to 8, along the stem. Along the reddish midrib of the leaf, on the underside, there are small spines.
Ludwigia grandiflora spp. hexapetala (Hairy Water Primrose)
This Ludwigia grandiflora grandlflora; the hexapetala subspecies is similar. Photo credits (for both): Richard Old, XID Services, Inc., Bugwood.org
Introduced as an ornamental, hairy water primrose has now infested the waterways from the mid-Atlantic southwards. It grows both horizontally and upright along the water surface and the shores. It forms large mats. Its leaves begin as rounded and shiny and then, after they emerge, become oblong with pointed tips. Stems turn from light green to reddish brown and hairy as the growing season progresses. Yellow flowers with 5 to 6 petals bloom throughout the summer.
Myriophyllum aquaticum (Parrot Feather)
Parrot feather has invaded the coastal regions of the United States. In North Carolina, it forms dense mats in the freshwater aquatic habitats and wetlands of the coastal plain and piedmont regions. It reproduces through dispersal of stem and rhizome fragments.
It gets its name from the feathery leaves (0.6 - 2") which can emerge or stay submersed. Emerged leaves are stiff and upright, submerged leaves are limp. The feathery appearance comes from being pinnately compound with 20 - 30 divisions per leaf. They whorl around a bluish-green (submerged) or brown (emerged) stem. The emerged stems also produce small white flowers during the spring.
It gets its name from the feathery leaves (0.6 - 2") which can emerge or stay submersed. Emerged leaves are stiff and upright, submerged leaves are limp. The feathery appearance comes from being pinnately compound with 20 - 30 divisions per leaf. They whorl around a bluish-green (submerged) or brown (emerged) stem. The emerged stems also produce small white flowers during the spring.
Myriophyllum spicatum (Eurasian Watermilfoil)
Photo credit (left to right): Richard Old, XID Services, Inc., Bugwood.org; Alison Fox, University of Florida, Bugwood.org
Eurasian watermilfoil was introduced in the 1950s; it has spread throughout the United States’ waterways causing the displacement of native plant communities. It grows in still or slow-moving waters, and has been reported in a few counties in North Carolina. The plant can reproduce from small fragments dispersed through the water or on boats. It is much easier to control an invasive species if we can manage infestations when they are still small. So, please watch out for Eurasian watermilfoil and report infestations outside of Halifax, Northampton, Perquimans, Tyrrell, and Warren counties to the N.C. Department of Agriculture and Consumer Services Weed Specialist at 1-800-206-9333.
Eurasian watermilfoil forms submersed rooted mats which are formed from a tangle of stems – stems can grow as long as 10’. The leaves grow in whorls of 3 or 4 around the stem. They are compound with tiny delicate leaflets of 12 - 21 pairs. Small yellow flowers emerge from the water on a spike (2 – 4” tall).
Nymphoides cristata (Crested Floating Heart)
Crested floating heart invades canals, lakes and ponds in southern states; although not present much yet in North Carolina, there is concern that it may become a problem if not detected early.
Each stem produces a single leaf which lies flat along (or right below) the water surface. The leaves are heart-shaped. They can be all green or green and red. Slender tuberous roots dangle from the stem-leaf node. White flowers bloom through the summer.
Each stem produces a single leaf which lies flat along (or right below) the water surface. The leaves are heart-shaped. They can be all green or green and red. Slender tuberous roots dangle from the stem-leaf node. White flowers bloom through the summer.
Salvinia molesta (Giant Salvinia)
Photo credit: Scott Robinson, Georgia Department of Natural Resources, Bugwood.org
Giant salvinia is a problem along the coastal plain of North Carolina (and other southern states). It spreads via vegetative reproduction, i.e., small stem fragments will disperse (often on boats) and form large dense mats. This plant is a problem in many parts of the world and degrades freshwater aquatic habitats by blocking light and depleting oxygen.
Young giant salvinia plants have leaves (0.5 - 1.5") which lay flat on the water surface, but as the plants grow the leaves become packed in tighter and overlap. As the mats get denser, stems of leaves will emerge upright. The emergent leaves are green, oblong, and are covered in arching hairs. The submerged leaves are brown and stringy and look like roots.
