From The Aquarium Wiki
Emergent is a word associated with the way aquatic plants are grown.
Many aquatic plants are in reality marsh or bog plants and are mass produced by keeping the plants leaves out of the water so they have maximum growth.
However these emergent plants tend to lose their leaves within a few weeks if submerged in an aquarium as the leaves have adapted to life in the air.
But usually the plant has survived and will soon put out new leaves which will be adapted for life under water.
- Typical companies that use the emergent technique is Tropica.