Hydrilla is an aquatic plant. It is usually considered to contain only one species, Hydrilla verticillata. It is also referred to as H. asiatica, H. japonica, H. lithuanica, or H. ovalifolica. Some characteristics are listed below.
Its leaves are about 2-4mm wide and 6-20mm long. They have pointed tips and saw-tooth margins. They have a rough texture because there are spines on the leaves. They are usually green while upper leaves are slightly yellow. The reason is that the sun can somehow bleaches leaves.
Hydrilla stem is very slender. It is only 1/32 of an inch wide. However, it can grow up to a length of 30 feet. Usually, it branches out near the water surface.
Its flowers are divided into two kinds: male flowers and female flowers. Male flowers can be white, reddish or brown. Female flowers are usually white. Hydrilla can be monoecious, which means both kinds of flowers on one plant, or dioecious, which means only one kind of flowers on one plant.
Hydrilla is a submersed plant. It can grow in almost any freshwater habitats such as springs, lakes, marshes, rivers ditches, etc. It can resist a salinity up to 7%. Its optimum growth temperature is 20-27 o C. It has low light compensation, which indicates the ability to grow in low light conditions. This makes it a competitive plant because it can grow in deeper water and begins photosynthesis earlier in the morning.
- Four ways to reproduce
- Fragmentation: Fragmented pieces can sprout into a new plant. The only requirement is that it has to contain at least one node.
- Tubers: The tubers are viable, too. Each one can produce as many as 6000 new ones.
- Turions: If turions are broken off and settled in sediments, they can grow into a new plant as well.
- Seeds: Unlike most plants, this is the least important way to reproduce for hydrilla. Perhaps it is because seed production is a good choice for long distance dispersal, which is usually not the case for it.
As introduced above, hydrilla can spread to new areas easily. Because of its good ability of growth, native aquatic plants will be shaded out until eliminated. Apart from the reduction of biodiversity, it is harmful to fishes as well, because thick mats of hydrilla can alter chemistry and oxygen levels. It also slows water flow greatly and interferes with boating severely. Thus, we have to take steps to control its growth.