Normally planted with native wetland plants, this floating plant raft is planted with lettuce

The concept of floating plant rafts reducing nutrients in stormwater intrigues me. The floating rafts can be planted with a huge variety of different plants. The plants do not have contact with soil, so they must get all of their nutrients from the water in the pond. Reducing nutrients in stormwater makes the pond more effective as a treatment device. It also reduces problems with ugly growths of algae and unwanted weeds.

We have been trying different types of rafts for seven or eight years. I am always very impressed with their appearance. Wetland plants, ornamental flowers and even some vegetables grow well on the rafts. (We don’t recommend eating vegetables grown in stormwater. I have lettuce growing on a raft in my recreational pond that does not capture stormwater.) Even though I have not measured their performance, the floating plant raft concept makes sense. I can’t help but believe they will be effective. The plants are much easier to establish on the rafts because the water level is always ideal and there are fewer problems with animals eating the new plants when they are anchored away from the shoreline. In a short time long, lush, thick growths of roots extend under the raft. The roots obtain all of the nutrients the plants need to grow from the water. The roots also provide excellent habitat for bacteria, micro-organisms, worms and insects. Little fish are attracted to the cover and supply of food. Larger fish are attracted to the small fish and shade provided by the raft.   

I began using foam rafts with holes cut for containing various size potted plants. We also tried some rafts that had holes cut in foam covered with coconut fiber netting. A special growing medium was placed on the netting in the depressions. Plants were planted in the growing medium and the roots grew through the netting into the water in the hole of the raft. We also tried thick recycled plastic matrix rafts. Plants were planted in growing medium in depressions in the raft. The plant roots would grow throughout the raft matrix and into the water. 

This is certainly a science which is still developing. The best design and best materials have not yet been determined. But, so far I really like a new raft system I am trying this year. It is called the BeeMat. They are distributed out of Florida. I had been aware of their product and had looked at their website. I was interested and decided to give them a try. My daughter goes to college in Daytona Beach, FL and I arranged to visit her and travel the short distance to New Smyrna Beach, FL to visit Steve Beaman, President and Owner of BeeMats. Steve has well over 30 years experience growing wetland plants in Florida. Steve and his owner son Forest now have a patent on the growing system. When I visited, Steve had many rafts planted with all kinds of plants in ponds at the farm. Some were even planted with leaf lettuce.

After I got back to work, we ordered a pallet of BeeMat materials to demonstrate the growing system to some of our clients. I mentioned the idea to a good friend of mine, Ken Walker, who owns Ken’s Produce and Garden Center on Hwy. 50 South of Garner, NC. Ken was very interested in the floating plant raft concept and decided to provide support by donating some leaf lettuce plants for me to try.

Here is the procedure I followed to plant the lettuce:

·         I removed the plant from the plastic growing tray and placed it in a bucket of pond water.

·         I rinsed all of the potting mix off the lettuce roots. (Rinsing off any soil is an advantage when planting natural wetland plants since you will be removing any duckweed, watermeal or other undesirable plants preventing their introduction.)

·         A small rectangle of coconut fiber matting is rolled around the bare root plant similar to a burrito.

·         The plant burrito is placed in a plastic plant pot containing slits cut in the sides.

·         A special clip is placed into two of the slits to keep the plant securely in the pot.

·         The same clip is used to secure the plant pot in a circular hole cut into the floating raft mat. (A 4 foot by 8 foot floating mat has 80 holes.)

Native wetland plants can be attractive while being very effective

The rest of the plant rafts will be planted with native wetland plants and deployed in clients’ ponds as demonstrations. I like the idea of being able to remove the plants from the raft in the winter. We will be removing all of the plant biomass resulting from the uptake of nutrients from the stormwater. The entire plants including all of the roots, stems and foliage is removed when the pot is removed from the raft.  When the plant is removed it does not die, decay and release nutrients back into the stormwater pond. Also, there is no raft of brown dead plants in the middle of the pond throughout the winter.

I have already picked enough of the big leaves off the lettuce to make three or four salads. The plants are doing fantastic. There are a few dead leaves that were touching the raft surface that I knew would turn brown and die. I checked the plants today, which was eight days from when they were planted and there still are no roots extending through the pots. I think it will be interesting to see how much of a root system the lettuce develops.

I know native aquatic plants will develop a heck of a root system since I have seen the mass of roots from pots I have planted in previous rafts. I just can’t help but believe floating plant rafts are going to reduce nutrients, improve performance and make stormwater devices more effective.  They are bound to be important to stormwater management in the future. I want our company to be pioneers in their utilization.

Foster Lake & Pond Management provides the full range of lake, pond and stormwater BMP services and products. These include: construction, repairs, maintenance, certified inspections, fish stocking, fisheries management, lake mapping, vegetation management, docks, fountains and aeration.

We have provided aquatic and stormwater solutions to our North Carolina customers for 30 years. Call us at: 919-772-8548 or visit: www.FosterLake.com