From time to time we get questions on floating vetiver on pontoons to remove nutrients from polluted ponds and lakes. Sometimes too we see efforts that have not resulted in well grown pontoon vetiver. This is normally because the plant was not first grown in pots on dry land. Here follows a note from Paul Truong on the subject:
"Here is the design I used in Australia, for a 1.5X1.5m pontoon, I used about 90 square pots. You can modify the set up to suit the material you use. Don't put young plants in the water first. You have to raise them first on dry land until you have well developed roots before putting them in the water and it is important to keep the crown above the water at all time, only the roots in the water. "