Several VFI plant options
Common Name |
Max. Height | Expected nutrient % uptake | Spacing | Literature |
1. Ditch Stonecrop Penthorum sedoides |
1.5 ft | Phosphorus, 0.43% | 1 ft | McJannet et al. 1995 |
2. Soft Rush Juncus effusus |
2 ft | Phosphorus, 0.2-0.4% Nitrogen, 1.0-1.5% |
1.5 ft | McJannet et al. 1995 |
3. Great Blue Lobelia Lobelia siphilitica |
2-3 ft | n/a | 1 ft | n/a |
4. Southern Blue Flag Iris Iris virginica var. shrevei |
3 ft | n/a | 1-2 ft | n/a |
5. Brown Fox Sedge carex vulpinoidea |
3.2 ft | n/a | 1 ft | Tanner et al., 2010 |
6. Cardinal Flower Lobelia cardinalis |
2-4 ft | n/a | 1 ft | n/a |
7. Swamp Milkweed Asclepias incarnata |
4 ft | n/a | 2 ft | Hochwendera, 1997 |
8. Wool Grass Scirpus cyperinus |
5 ft | Phosphorus, 0.3% Nitrogen, 1.5% |
2 ft. | McJannet et al. 1995 |
9. New England Aster Symphyotrichum novae-angliae |
5 ft | n/a | 2 ft | Lubnow, Fred S., 2014 |
10. Soft Stem Bulrush Scheanoplectus tabernaemontani |
6 ft | n/a | 1 ft | Wang et al., 2014 |
11. Angelica Angelica atropururea |
6-9ft | n/a | 3 ft | Lubnow, Fred S., 2014 |
12. Cutleaf Coneflower Rudbeckia laciniata |
7 ft | n/a | 4 ft | Lubnow, Fred S., 2014 |
13. Prairie Cordgrass Spartina pectinata |
8 ft | Phosporus, 0.2% Nitrogen, 0.5-1.0% |
2-3 ft | McJannet et al. 1995 |
Plant spacing estimation chart
This is a typical plant spacing chart that you can use to determine the number of plants needed for a project. To use the chart, you will need 1) the recommended spacing (found in the table above) for the species you select and 2) the area in square feet of your VFI. The recommended area of a VFI for maximum water treatment ability is 10%-20% of the surface area of the small pond or lake being treated.
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Image source: Wilson Bros Nursery
Plant Growth & Maintenance
Plants on the VFI can be expected to reach 1/2 to full size in the first growing season. Larger species, like Prairie Cordgrass, will likely only grow to 3/4 their mature height, because they are growing hydroponically. As the plants mature, they will fill in the surface of the VFI, and will form a dense root mat underneath the island. In the fall, the plant material should be trimmed with clippers and removed to a landfill. If left to overwinter, the vegetation will drop to the lake bottom, and as it decomposes, will return the removed nitrogen, phosphorous, and other stored pollutants back to the water! |