Description
The floating islands are located on top of the duck pond. This pond is a central point of StellaLou Farm, both directionally and in elevation.
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After observing the effects of low plant life, substantial sun, and the nutrient of duck droppings in the smaller pond, we began planning ways to bring aquatic health and balance to this space. The pond was added during the improvements to dwellings on the property and as part of the stormwater management plan, takes on drainage from both the barn and the southern house. The pond is lined with bentonite, a type of clay, which has successfully held the pond water without the introduction of plastic. In the first two summer seasons with this pond, the top became completely covered with algae.
The floating islands will be home to the addition of native aquatic plants that simultaneously oxygenate the water and utilize the excess nutrients. These two functions should balance the factors that have led to the pond’s murkiness and algae proclivity.
Using the aggressively growing bamboo on the property has been a goal with our outdoor construction projects, as it is very strong and available. Additionally, the bamboo, with it multiple hollow chambers, helps to keep the islands buoyant.
Bonus features of this design include providing safe settling places for honeybees and insects to drink. This additional edge environment has added habitat for frogs and their tadpoles. We look forward to greater wildlife diversity, and are already loving the visual addition to the space.
Process and Timeline
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Observation (2019): The duck pond had its first season in 2019, and we took some time to see how the different elements, including flora and fauna, responded and effected this space. In 2020 we had a particularly thick bloom of algae, which confirmed our concerns about the balance of the elements in the ecosystem. Duck pond before intervention
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Research (2021): We began considering how we could use biochar to filter the pond and then be removed to disperse the excess nutrients to planting areas elsewhere on StellaLou. We decided to take a visit to our dear friend, Dale Hendrick's permaculture haven to chat about this possibility. He excitedly steered us in the direction of floating islands with a biochar bed attached. In our experimenting with this concept, we failed, for a variety of reasons but were left with a strong desire to create plantable islands, and consider the biochar separately at another time. We decided to move forward with bamboo, as we have the material in excess, and found some helpful youtube videos to base our own style of floating island on.
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Design (2022): Since our floats were created in a grid format, we used a table in a digital document to experiment with how to incorporate multiple native pond plant species together. We considered the height of each plant, the horizontal space, spread rate, plant availability, and aesthetics in these designs, in slide deck below.
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Raft Creation (2022): Each raft is constructed of two bamboo grids (seven 42" lengths of bamboo horizontal, and seven vertical, lashed together with waxed twine along the outside edges). Sandwiched between is a 3-6' mat of coconut coir folded in half, with bamboo twigs/leaves and straw as a substrate nestled in the middle (about 9" depth of straw and bamboo). This sandwich was then tied together at the edges with more waxed twine.
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Planting (2022): We were able to secure a wonderful variety of native plants from Wicklein's Native Plants in Baltimore, Md, a little over an hour away. They were very responsive, friendly, and accommodating. Once we got the plants home, we loosely followed our designs, cutting into the top of the coconut coir to plant into the raft. We made some edits to designs once we felt the weight of various plants, in an attempt to balance the island well on water.
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Floating (2022): Once the islands were floated on the pond, they took on water as planned, with the top coconut coir wet but above the surface and top bamboo layer full out of the water. Over the course of a week, they sunk a little more than we planned. We fabricated a watertight floatation square to tuck under each island out of 2" pvc tubing and elbows.
What We Have Learned & What's Next...
We enjoyed the first three islands so much that we decided to add a fourth. This time we attached the PVC float underneath ahead of time, which was much easier!
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All plants are currently alive and well, some are positively thriving. We are at a point of observation again. We will observe the plants and the water quality before making any more changes. We have not anchored the islands in any locations in the pond yet, and will continue to observe before doing so. The desire is for the plants to spread, and we do not yet know what will happen to the island itself as that happens. Will the roots reach down to the pond bottom, as it is very shallow, naturally anchoring them? Will they sink due to this or disintegrate? We will watch and see.
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(2022) We have one island which is sinking due to the size of PVC we used on that particular one and the PVC float isn't tied to the bamboo. Two islands are particularly strong and have rooted themselves very close to the pond edge. The water is actually getting a bit clearer! The duckweed is beginning to spread quite strongly and we have a new algae, Water-net Algae. These are removing nutrients from the pond. These provide food for the ducks and likely other creatures as well. As they cover more area, we will pull it out (quite easy to do) and add it to the compost to fertilize the garden. The only plant that was not successful was the water lily.
Plant List
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Sweet flag (Acorus americanus)
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Soft rush (Juncus effusus)
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Water willow (Justica americana)
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Arrow arum (Peltandra virginica)
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Pickeral rush (Pontederia cordata)
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Duck potato (Sagitteria Latifolia)
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Lizards tail (Saururus cernuus)
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White fragrant lily (Nymphaea odorata)
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Copper iris (Iris fulva)