Deep-Planting Willow Cuttings Using Hydraulic Jetting

Paper Summary

Planting willow cuttings for streambank erosion control is an ancient technology, revived in recent decades as part of "bioengineering." Problems include difficulties with emplacement, which frequently consists of pounding them in as stakes, and slumping can easily undermine the short cuttings normally used. We have implemented a new hydraulic jetting technique which can rapidly (20-30 seconds) open planting holes in silty/sandy streambank alluvium, which are 2 meters deep by 3-5 cm diameter. Slender dormant willow cuttings 3-4 meters long pushed into these holes extend to damp soil and can sprout roots their entire below-ground length. The technology consists of a specially machined jetting tip welded to a 2 meter length of ordinary 1.3 cm (½ inch) steel pipe. Two of these jetting pipes are connected to a portable high-pressure pump, drawing water from the stream and delivering it to the jets via sturdy garden hoses. A planting team of 4 is most efficient, with 2 persons jetting holes and 2 planting willows. At favorable locations, a team of 4 can harvest 1000-1500 slender willow cuttings per day and deep plant 1000 cuttings per day. All the equipment is portable and can be carried on muddy stream banks. The jetting equipment plus 1000 bundled willow cuttings fit into a pickup truck. When properly planted, survival rates for fully dormant spring plantings of sandbar willow consistently exceed 95% in Iowa.
A "blueprint" for machining the jetting tip is published in the proceedings. It is not patented and readers are invited to test the technique on their own streambanks. A complete package of jetting equipment can be assembled for about $750. In colluvial/alluvial silts and dirty sands the jet pipe can be merely guided down and will penetrate 2 meters in about 15-20 seconds. In sediments with scattered stones, compact clay layers, shells or rotten logs, penetration is aided by pushing and twisting the jet pipe. If the hole does not reclose around the cutting, the jet can be used to wash sediment from upslope into the hole. Planting the cuttings 2 meters deep leaves 1-2 meters to protrude above small floods and initiate leaf growth above grass and weeds. Contrary to popular opinion, we find that willows do not root much below the permanent water table. As a "stand alone" technology we suggest that deep planted willow thickets will only prove serviceable over decades when planted along streambanks fed by abused watersheds of less than 8-26 km2 (3-10 square miles). In larger watersheds, if the toe of each outside meander bend can be reinforced with riprap, gabions, interlocking concrete polyhedra, anchored root wads or anchored lunker boxes, then deep planted willows may serve to help stabilize the areas above and around these units at modest cost, while providing habitat and esthetic benefits.

Rick checking root development.

Rick with hydraulic jet.

Wayne in first year's growth.

Deep planting willow cuttings using hydraulic jetting.