Oasis is the name of a porous foam used in flower arranging that holds water in the green form and is used for dry arrangements in the brown form. It is a soft Styrofoam like material. It can be trimmed to fit the container, packed tightly and taped into place for stability and in turn lends stability to the plant material being stuck in it. This allows the arranger the ability to arrange flowers and/or other plant materials in a variety of angles.
Green Oasis should be soaked in water for a few hours before using to eliminate all the air in the foam, which will help cut flowers to absorb water instead of having the stems clogged with air.
The stems continue to absorb water as long as the green oasis is kept moist. Oasis can be reused until so many holes have been made in it that it falls apart. Aside from that it is inexpensive to start with.
Oasis can be cut flush with the container or it can be cut to stick up above the container allowing plant material to hang downward by sticking it into the oasis in an upward manner.