The Vetiver (approximately 18 plants) was planted in a concrete treatment box in a special media "One of the ways we get the Vetiver to grow so quickly is we don’t use any soil. It’s a soil-less media made consisting of expanded aggregates and a proprietary hydroponics media. This allows for fast growth." Over a period of 15 months the plants put out a massive root system, and in doing so resulted in high uptakes of N, P and a range of heavy metals.
The Vetiver was trimmed at intervals, and was dug up after 15 months
Here follows some images: