DA-15-00001 Palomino Fields Master File

Home Browse Search

Willow Clump Plantings J. Chris Hoag, Wetland Plant Ecologist, Plant Materials Center, Aberdeen, Idaho Introduction: Willow clump plantings are a streambank soil bioengineering technique that can be used when large stands of willows are available in the project site area. This Streambank Soil Bioengineering technique harvests an entire live willow clump including the above ground stems and roots. This method unlike pole cuttings, already has part of the root system present, so the willow doesn't need to grow as many new roots from scratch. This results in a significant advantage for the plant in terms of shortened establishment period, lower failure rate and faster protection of the problem site. Another principle that makes this technique desirable is that willows are depositional plants. Willows generally grow in riparian areas and on flood plains that commonly receive sediment from upstream sources. Some of this sediment deposits around the stems when stream flows bring high sediment laidened water that flows through the willow stems, slowing flow velocity and thus dropping sediment. Willow stem collars (where the stem meets the root material), unlike conifers for example, do not need to be at the soil surface or slightly below the soils surface in order for the plant to survive. When sediment is dropped out of the water column, it accumulates around the stem. As the stems are covered with sediment, the root buds in the stem swell and start to sprout roots. This is one way willows increase their root mass. This also results in more stems and leaves. This ability to adapt to sediment deposition makes willow clump plantings a great Streambank Soil Bioengineering technique especially on channel reconstruction projects, for stabilizing outside meanders, areas where cuttings are difficult to plant, and where soil conditions such as saturation or very fine soils make it difficult for willow cuttings to establish new roots. Willow clump harvesting and planting methods • This method should only be used where willows cover extensive areas of the floodplain or meadow areas. In addition, the willow stand should show good regeneration over the area. • Locate willow clumps that are young and vigorous, about 8-20 feet tall, and about the diameter of the backhoe bucket. Dig straight down and under to the willow clump root mass. Start the hole about 10 inches away from the stems and dig down about the depth of the bucket (approximately 2 feet). Try to get about 70% of the root mass. 2 s moi* y 1 f 1 ti. r �•- Jt 2