Purple loosestrife

Scientific Name: Lythrum salicaria
Common Name: Marsh Monster
Description: The purple loosestrife has attractive purple flowers that come off from a green stem. They can grow to be fairly tall as well as a bright purple.
Reproduction: The Purple Loosestrife can produce two to three million seeds while budding.
Problems Caused: Purple Loosestrife is an invasive plant in wetlands. It's had become an issue in all states but Florida. They can double in an areas almost over night so pulling by hand to get rid of Purple Loosestrife is not an option.
Prevention: More than a dozen biological controls have been studied and released onto these plants. It is imperative for researchers to find even more forms of pesticides to kill these invasive weeds.

Salvinia

Scientific Name: Salvinia molesta
Common Name: Giant Salvinia
Description: small free floating plants that grow in groups and form thick mats over the top of the water. They can also double in size in in four to ten days under good circumstances.
Reproduction: Giant Salvinia reproduce by fragments that fall off. As well as budding from the plant.
Problems Caused: Giant Salvinia reduces oxygen exchange and negatively effects water quality and ecosystem habitat.
Prevention: In order to prevent Salvinia from entering the ecosystem it is advised to never put aquarium plants into the lakes or wetlands.

Water Lettuce

Scientific Name: Pistia stratiotes
Common Name: Water Lettuce
Description: Water Lettuce looks exactly what it sounds like. A open head of lettuce found within the water. Although it's leaves are much wider and longer they are easy to spot. They are also free floating plants.
Reproduction: Water Lettuce reproduces through daughter plants.
Problems Caused: Water Lettuce form large mats on top of the surface preventing oxygen and sunlight to the rest of the body of water.
Prevention: In order to prevent Water Lettuce there are pesticides that can be harmful to the person spraying. In which case it is important for the person to remember to wear all appropriate safety gear when destroying water lettuce. Although it may not be as quick as some of the other weeds it is just as destructive to the environment.

Water Hyacinth

Scientific Name: Eichornia crassipes
Common Name: Water Hyacinth or "The World's Worst Weed"
Description: Beautiful purple flowers with green petals and shoot. This was originally brought from South America because of their delicate and pretty color.
Reproduction: The Water Hyacinth can produce two to three thousand seeds as well as reproduction through daughter plants. It is one of the fastest growing plants known.
Problems Caused: The Water Hyacinth takes up nutrients from the water and in turn produces H-ions that acidify it killing the life. The dense mats it forms on top of the water lowers the levels of oxygen as well as blocks navigation in the water.
Prevention: In order to prevent Water Hyacinth many scientists have discovered that you can spray pesticides that will kill the weed. However it is quick to grow causing the damage and the fixing of bodies of water to play a nonstop game of cat and mouse.

Eurasian WaterMilfoil

Scientific Name: Myriophyllum spicatum
Common Name: Eurasian Watermilfoil
Description: When the water milfoil is growing stems are red. However it is mostly found green and is a submergent plant.
Reproduction: The Watermilfoil is spread by seeds as well as fragments breaking off. It has also been spread by birds that have carried it across America.
Problems Caused: The Watermilfoil shades the needed sunlight from the water causing suffocation and death to the plants and animals. It also impedes navigation in the water.
Prevention: In order to prevent Watermilfoil from spreading there are fish that specifically eat plant life. Unfortunately this is risky and the only fish that can be introduced to the weeds must be sterol so that their population can not multiply and destroy the ecosystem.

Hydrilla

Scientific Name: Hydrilla verticuillata
Common Name: Hydrilla
Description: Grows from bottom of ocean to the top. Long green shoots that extend upward with petals around it.
Reproduction: Through Tubers, Turions, stolons and fragments. They do not have seeds. However they can grow more than an inch a day and because they are so fast growing it is extremely hard to control.
Problems Caused: Hydrilla also shades out desired sunlight and impedes navigation in the water for vegetation.
Prevention: In order to prevent the spread of Hydrilla boat owners must sufficiently clean off all parts of the boat before taking it anywhere else. For instance Hydrilla could get caught on a propeller, in which case it is imperative the owner hose off their boats then burn the Hydrilla or at least throw it into the garbage.

Alligator Weed

Scientific Name: Alternanthera philaxeroides
Common Name: Alligator Weed
Description: White flowers in center with green leaves stretching out of different sides that are pointed.
Reproduction: Alligator Weed can spread through seeds as well as plant fragments being dropped.
Problems Caused: The problems caused by Alligator Weed is extremely aggressive. They form mats along the surface of the water. They always get in the way of water navigation and can bring harm to the vegetation if not treated. By not allowing sun to enter the water Alligator Weed is causing plant death.
Prevention: The best way to prevent Alligator Weed is by spraying the area of the weed with herbicides or taking large machines and digging up the weed life trying to end it's spread.