Installation Tips and Maintenance
Here are some recommendations to help ensure that your project is installed properly and that it succeeds over the long term:
- The importance of protecting young plantings from wildlife in search of food (primarily geese, ducks, muskrat, and deer) cannot be overemphasized. While wildlife habitat enhancement is an important goal of bioengineered shoreline restoration projects, until the new plantings become established, grazing and uprooting of tender plantings can seriously undermine the project's structural integrity. If waterfowl predation is threatening the integrity of the planting beds, waterfowl exclusion fencing can be installed around the perimeter of the planting beds (e.g., black plastic fencing, 4 feet high with 1-inch-square openings and attached to steel T-posts driven into the shoreline on 5-foot centers). Ideally, the fencing should be left in place for one or two years until the plants are mature enough to withstand occasional defoliation by waterfowl. One particular plant used in this project, common arrowhead (Sagittaria latifolia), has proven to be so susceptible to waterfowl grazing that the Garden no longer recommends its use in shoreline projects where waterfowl are expected to be present.
- Plant plugs installed below the normal wate line can be secured to lakebed soils with one or two 6-inch sod staples. These staples protect the plants from being washed away by waves during high wind events, and the staples keep the plants from floating out of their planting hole in the event of unusually high water or flood conditions. The staples also provide exceptional protection from waterfowl grazing: while the waterfowl may be able to defoliate the plant's top growth, the staples prevent the waterfowl from destroying the plant's crown and/or completely plucking the plant plug right out of the lakebed. Since these staples are made out of metal, they will corrode and degrade over time. Nevertheless, because of their sharp points, their use in shorelines near public beaches and other access points should be carefully evaluated.
- The removal of invasive plants and weeds in the planting beds is an ongoing maintenance issue for all "bioengineered" shoreline erosion techniques. This is especially true during the first two years after installation, when spaces between the new plantings allow plenty of sunlight to reach the soil surface and stimulate the growth of new weeds. Like any perennial garden, as the new plants mature with time, the emergence of weeds and other unwanted plants is lessened. However, inherent to the shoreline zone is the ever-present drift of new weed seeds riding along with incoming waves. In particular, plants such as purple loosestrife (Lythrum salicaria) and black alder (Alnus glutinosa) have been troublesome at the Garden. A commitment to diligent removal of these invasive plants at a young stage of growth — and in all cases before they set seed — is particularly important.
- Most of the project's planting beds utilized a plant plug spacing of 12 inches on center. While wider spacing is frequently and successfully used in prairie restorations and other relatively flat environments, the inherent instability of the shoreline slope demands that the new plantings become established and provide their soil anchoring properties as soon as possible. While 12-inch spacing is highly recommended for shoreline applications, a wider spacing (up to 15 inches) can be utilized if the new plants are in excellent condition prior to planting, and sufficient maintenance resources are available to ensure that the plants can grow quickly after installation.
- Hand-spreading seed of needle spike rush (Eleocharis acicularis) along the wet edge of completed shoreline planting beds can provide a "cover crop" of plant biomass that provides significant stability to the shoreline soils while the plant plugs take root. This quick-growing plant also provides an attractive carpet of green color between the plant plugs and brings a more "living" aesthetic to the shoreline, especially during the first few years. However, prolonged periods of high water can damage this plant, and so it may not perform well if excessive water fluctuations are experienced.