Drainage Design Manual - the City of San Luis Obispo

follows: availability and cost, collection and handling ease, storage ease, planting ease,presence of disease, elevation of the site, and the urgency of need for cover.Special care should be taken to avoid contamination of native gene pools by notintroducing species and/or subspecies capable of hybridizing with plants that occurnaturally at a project site. Where possible, it is desirable to use native species indigenousto the San Luis Obispo area, and propagation materials should be collected from localsites. If this is not possible for certain species, materials can be collected fromcomparable areas in the Central Coast area. When collecting seed from a particular site,attempt to insure the greatest possible genetic diversity by including a large and diverseset of plants. Randomly collect from plants within a population and among differentpopulations. Avoid collecting plants from areas with special limiting conditions (i.e.,such as the presence of serpentine soils) unless the revegetation site has similarconditions. Because revegetation planting is best conducted during the fall and earlyspring, planning to insure availability of plant materials at these times is essential.Depending on plant material specifications for a revegetation project, lead-time forcollecting and propagating suitable plants can be as high as two to three years.The nursery industry typically supplies plant materials in 4, 19, 56-liter (1, 5 and 15-gallon) container sizes. Some native plant materials are available in these container sizes.Within the last several years, native plant materials have become available in containersthat are more suitable for revegetation projects in environments that will receive minimalmaintenance. They include leach tubes or Supercells 38 x 200 millimeters (mm) (1.5 “x8"), Depots 63 x 254 mm (2.5" x 10"), Treepots 101 x 355 mm, 152 x 406 mm, and 203 x457 mm (4" x 14", 6" x 16", and 8" x 18"), Treebands 57 x 127 mm (2.25" x 5") withopen bottoms), rosepots 57 x 76 mm (2.25" x 3"), various grass plug pot sizes, andothers. Selecting the right plant container sizes for a project depends on several factors.These include cost factors, site conditions and adaptability factors, availability of plantmaterials, and issues related to public perception of the project.Selecting the right plant container sizes for a project depends on several factors. Theseinclude cost factors, site conditions and adaptability factors, availability of plantmaterials, and issues related to public perception of the project. There are differences inthe cost and required duration of maintenance associated with different container sizes.Because small container plants are cheaper to buy than large container plants, andgenerally require less maintenance time to become established, using them can result insome cost savings.Native plant materials are not always commercially available, and they are rarelyavailable in the quantities required for most revegetation projects. Because of this, it isoften necessary to specify plant material procurement procedures in a revegetationdesign. An increasing number of nurseries specialize in growing native plant materialsfor revegetation projects on a contract basis. If a project requires using plant materialspropagated from vegetation growing on or near the project site, some of these nurserieswill make arrangements to collect seeds, cuttings and other propagation materials fromthe area. Because of the lead-time necessary to collect propagules and grow revegetationSLO Creek Drainage Design Manual 144 February 2003