Live Stakes and Fascines in Western Oregon and Western Washington
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Stem Cuttings Some deciduous woody plant species rapidly form adventitious roots from stems and can be easily propagated in the field with dormant stem cuttings stuck in moist soil. Field propagation of cuttings can reduce or eliminate costs, both for materials and labor, allowing increased planting density and volunteer-based restoration without a cash budget. Cuttings can be planted in environments where potted stock cannot. Pacific Northwest indigenous species have been poorly studied and limited research is available to guide harvest, storage and installation methods. Context Stem cuttings are an inexpensive approach to plant propagation and can be an integral part of an erosion control plan. Dense cutting plantings can be useful for weed control by providing rapid competition for light and are a valuable resource to support cash poor volunteer-based projects. Cuttings provide a low cost option for adaptive management intervention. Hydrology and soil structure along the wetland to upland gradient may strongly impact a cuttings ability to form roots in the field. Several hardwood trees, rhizomatous shrubs, and tree-like shrubs associated with riverine and wetland environments are viable for cutting propagation. Some species may require wildlife protection as deer and beaver browse can damage cutting plantings. Large cuttings have been used as an anchoring method in large woody debris placement. 1. Selecting Species 2. Harvest, Storage and Pretreatment 3. Site Selection and Planting Methods 4. Revegetation Strategies and Maintenance Selecting Species Adventitous root formation is an adaptation to alluvial disturbance where new roots form from stem tissue in response to environmental conditions (Gill 1975; Krasny et al. 1988). Many native species have demonstrated the ability to establish when planted as dormant stem cuttings, but success is species specific and dependant on environmental conditions (Cereghino 2004; Darris 2002a; Flessner 1997; Stannard & Guenther 1999). Many more experimental stake plantings have been completed by regional practitioners but are poorly documented. The following list is a tentative list of species with sources of additional information listed for each species: Plants commonly used in restoration projects: Corunus sericea (Cereghino 2004), Populus trichocarpa (Stannard & Guenther 1999), Salix hookeriana, Salix lucida (Stannard & Guenther 1999), Salix scouleriana (Edson et al. 1995), Salix sitchensis Paul Cereghino – 22 Jan 2006 Page 1 of 7 Plants with multiple or well documented reports of success but limited use: Lonicera involucrata (Darris 2002a), Physocarpus capitatus (Darris 2002a; Darris 2002b), Spiraea douglasii (Darris 2002a, Hennelly 1994, Stamphli 1992), Symphoricarpos albus (Cereghino 2004; Darris 2002a; Darris 2002b), Philadelphus lewesii (Darris 2002a) Plants with poorly documented reports of success, or success under specific conditions: Malus fusca, Oemleria cerasiformis (Darris 2002a), Ribes sanguineum, Rosa gymnocarpa, Rosa nutkana, Rubus spectabilis (Cereghino 2004; Darris 2002a; Darris 2002b), Sambucus racemosa Plants that can be propagated by cuttings with an unknown ability to establish in the field: Oplopanax horridus, Ribes bracteosum, Ribes divaricatum, Ribes lacustre, Ribes laxiflorum, Rosa pisocarpa, Rubus leucodermis, Rubus parviflorus, Rubus ursinus, Vibernum edule Where species do not root as readily as willow, pretreatment and proper timing may be critical to success. Some species, like red elderberry (Sambucus racemosa) and indian plum (Oemleria cerasiformis), break bud extremely early in the growing season. Stewards testing these species should plant early, well before bud break. Species with a pithy core, like salmonberry (Rubus spectabilis) (which also roots poorly from older wood) and red elderberry, may loose moisture quickly and may benefit from horizontal planting as a fascine or with stems buried under mulch (Darris 2002b). In general, easy-to-root species tend to do well regardless of the subtleties of method, while the full palette of species may only be available to those willing to experiment and learn the needs of each species. Cutting propagation is cloning and revegetation with limited genetic variation may produce plant populations that are less able to adapt to disease or changing environmental conditions. A species may develop local genetic populations that are adapted to local conditions and the environment of the parent material and the conditions on the site may have an influence. The genetic patterns of native plant populations have not been studied, and so actual affects are un-documented. Harvest, Storage and Pre-treatment When a stem is cut it begins to die. It must form roots before it dries out or rots. Maintaining stake moisture levels is the critical objective that drives the majority of harvest, storage and pre-treatment procedures. Stakes can be obtained from donor plants on site, power line rights-of-way, salvage sites, infrequently cut roadsides, infrequently mowed stormwater detention ponds, old pastures, or any other site where native woody plant growth is present but unwanted. A number of contractors working independently, or through retail or wholesale native plant nurseries, will provide pre-cut stem materials for 25-40 cents a foot. Harvest may degrade the donor plants by spreading disease or by creating an opportunity for competing vegetation. Suggestions for reducing impacts on donor plants include: reducing the number of stems cut per plant, leaving over 8 inches of stump on cut stems, and cleaning pruning tools between plants. Wild cutting should be limited to sites where there would no consequence from degradation of parent material. No agricultural production of indigenous cuttings has developed in our region, although agricultural cutting blocks are part of the Poplar forestry industry. Flooding can stimulate adventitious rooting (Gill 1975; Krasny et al. 1988). No tests have been conducted to determine if stakes taken from plants under inundated soil conditions have a higher rooting ability than cuttings from plants in drier soils. Variation in rooting ability between populations within a species has been documented (Puri & Swamy 1999), but differences in rooting ability among indigenous northwest species populations has not been studied. Larger cutting diameter has not been clearly shown to improve rooting ability in all species (Cereghino 2004). As long as rooting ability is sufficient, larger stems may provide some value in their ability to survive installation, and resist desiccation. Pole cuttings using tree trunks have been successful established for willow (Salix spp.) and black cottonwood (Populus trichocarpa)(Bentrup & Hoag 1998). Stem age may strongly control rooting ability, with younger stems rooting more successfully than older stems among species sensitive to stem age (Darris 2002a). Paul Cereghino – 22 Jan 2006 Page 2 of 7 Adventitious roots that form at nodes may constitute a significant portion of the rooting ability of some species. Higher nodal density may increase the number of roots formed in the rooting zone, thus increasing survival and growth. red-twig dogwood (Cornus sericea) has had high mortality on stakes with only one or two sets of buds (Cereghino 2004). Some suggest transporting whole branches to reduce water loss (King County 2004; Schiechtl & Stern 1996) while other process cuttings in the field for easy transport (Cereghino 2004). No controlled comparisons have been documented. Numerous studies suggest that there is no loss of rooting ability after storage as long as the stakes remain dormant and moisture levels are maintained. Stakes have been wrapped in plastic and refrigerated, or buried in moist sawdust or snow with success. (Bentrup & Hoag 1998; Fischenich 2001; Schiechtl & Stern 1996). Both near- freezing and below-freezing storage have been successful for Populus (Cram & Lindquist 1982; Chmelar 1974; Hoag & Short 1992; Phipps & Netzer 1981). Below freezing storage may require transitional storage for 2-3 weeks at 41 degrees F to provide time for buds to emerge from dormancy (King County 1993). Storage under cool moist conditions may improve rooting ability in some species by allowing time for formation of root primordia before exposure to the stresses of outplanting (Cram & Lindquist 1982; Dirr 1998; Hartmann et al. 1990), and cold moist storage should be considered as a pretreatment when testing an infrequently used species. Study of cutting storage has been limited to willow (Salix spp.) and poplar (Populus spp.). Cool moist storage may encourage root formation and root formation prior to planting may be undesirable. Some have suggested cold dry storage followed by soaking to reduce root formation (Jacobson, 2005) Moderate levels of hormone treatment (0.3% IBA) have improved rooting ability in Scouler’s willow (Salix scouleriana) (Edson et al. 1995) other trials have indicated no benefit or even loss or rooting ability among indigenous species (Darris 2002a; Hoag & Short 1992). Soaking stakes before planting may increase rooting ability, but results have been inconclusive (Hoag 1993). Increased soaking time may improve rooting ability, and soaking may allow cuttings to overcome the stress of dry soil conditions(Hansen & Phipps 1983; Schaff et al. 2002). However, soaked cuttings should be planted before roots rupture and emerge from the bark, which can occur in as little as two to ten days depending on the predisposition of the cutting. No systematic study of soaking