Najas guadalupensis (najas grass AKA guppy grass) is a species of aquatic plant known by the common name common water nymph. It is native to the Americas, where it is widespread. It is also known on other continents as an introduced species and sometimes a noxious weed. This annual plant grows submerged in aquatic habitat types such as ponds, ditches, and streams. It produces a slender, branching stem up to 60 to 90 centimeters in maximum...