Wattles is an Old English term that's over 800 years old that refers to the use of intertwining live branches to secure slopes along shorelines.
Description
Wattles and live stakes are part of a bioengineering approach to shoreline management—the use of live vegetation for erosion control. Live stakes are cuttings from shrubs that are also used to stabilize slopes.
Wattles, also called live fascines, are bundles of live branches used at the toe (bottom) and on slopes for stabilization and to introduce new plant material. Wattles reduce water velocity, trap sediment, and hold soil in place.
Both live stakes and wattles will sprout and grow, forming a living stabilization system.
Preparation
Live stakes and wattles are cut from readily sprouting woody species while they are dormant (i.e. early spring or late fall). The best species to use are native willows. Dogwoods are also a good choice. A harvest site must be located. Look for an area with an abundance of shrubs of the desired species. With permission from the landowner, harvest the amount of material needed. Carefully prune only parts of each plant to ensure its survival and limit the visibility of the removal.
Live stakes are cuttings of dormant shrub branches 2'-3' long with a diameter of about 1/2"-1". Each branch may be cut into multiple stakes using loppers. Cut the top flat and the bottom at a diagonal to make for easier installation and identification of the appropriate end to be placed in the ground.
For wattles, use longer cuttings of the woody species. Cut branches 5'-10' long or longer and place them in bundles 6"-8" in diameter. Stagger the branches to create longer wattles and distribute the tops throughout the length of the wattle. Use untreated twine or wire to tie the bundles together tightly (photo left).
List of species appropriate for bioengineering:
See the "Starter Lists" in the Native Plant Encyclopedia.
Planting Tips
Live stakes are planted using a small sledge hammer or dead blow hammer (photo). Carefully pound the stake into the ground at a right angle to the slope leaving about 1/5 of the stake above ground. Trim off damaged tops. Stakes can also be planted by creating a pilot hole with a metal rod. Make sure to tamp the soil around the stakes to ensure good soil contact.
Wattles are installed at the toe (bottom) of the slope by excavating a trench similar in size to the wattle. Place the wattle in the trench and stake it in place using dead stakes through the wattle and live stakes at the base of the wattle. Bury the wattle, leaving just the top slightly exposed. Excavate additional trenches on the contour of the slope spaced 3'-7' apart depending on the steepness of the slope and erosion potential. Install wattles in each trench as described above. A loosely woven jute or coir erosion control fabric can be placed underneath the wattles and staked up the slope for extra erosion control, especially for slopes that have been regraded.
Plant the areas between the wattles and live stakes with native grasses, sedges, wildflowers or other shrub species. On exposed soils, a cover crop of annual grasses should be used to provide temporary stabilization until the shrubs and other plants are established.
Maintenance
The shrubs may be pruned if they grow too large. The willows are often just pioneer species that may eventually be replaced with other plants that grow on the shoreline. Periodically inspect the site to look for damage from animals, weather or other sources. Check for sprouting success and replant areas that need attention.