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PLANT MATERIAL SELECTION Plant malerial selection should be made based on evalualion of Ihe following factors: site conditions, desired visual quality, seasonal aesthetic charac- teristics, maintenance requiremenls, available mainlenance budget and waler availability, Empha- sis should be placed on selecl/ng nalive species and Ihose 'adapled', or naluralized, species wilh drought lolerance characteristics which respond well 10 Denver's climatic varial/ons. Natives not only add a regional 'lIavor' to Ihe landscape, but once eSlabljshed are more drought and strass tol- oranl than non-natives and often require minimal mainlenance, There are many native and drought tolarantlandscape species, Including allernate turf grasses, Ihat can be substituted for bluegrass and the more 'lradilional' higher waler demanding planls without a loss in the visual qualily of the landscape. Plant selection should also focus on lhe provision 01 seasonal color and accents: spring, summer and fallllowering plants, fall foliage color change, Interesling grass plumage/seed head, evergreens and olher accent material for winler cotor, The salt used in Colorado winler roadway mixes adds another concern 10 species selecl/on, loca- lion 01 planl/ngs and malnlananee. Thera ara many species available for landscaping which have bolh droughl and alkaline tolerance characleristics, More alkaline tolerant species should be used in the planl/ngs that are closest to the roadway and those planling areas closa enough to be a/teclad by sail may need 10 be lIushed periodically to leach oul deposils, No bluegrass is to be used in relandscaping this portion of the 1-25 corridor. Turf seleclion should concenlrale on Ihose species, bolh nal/ves and al- lernale turfs, which combine drought lolerance characleristics with reduced maintenance needs, Warm season grasses require very IIl1le supple- mental water to keep visual quality high, but have a longer dormancy period than cool season grasses. Besl growth lor these grasses occurs In tha sum- mer, A visual plus is the eveness 01 color dis- played by these grasses during dormancy. Cool season grasses remain green longer, but are more mottled in appearance when dormant. Best growth for cool season grasses peaks In both spring and fall, Again, emphasis must be placed on matching the grasses wilh Ihe correcl sites. Warm season grasses cannol be placed In a shaded location, as they will fade out and allow Invading species to dominate, Native butfalograss is extremely droughllolerant, but will not form turf density with- oul some supplemenlal water. Yet iI overwatered, bultalograss will begin to fade and allow other grasses to establish. See Appendix B for plant material suggestions. OTHER PLANT MATERIAL SELECTION RECOM- MENDA TIONS . For steep embankments/slope plantings, use plants Ihal will be compelititve with weeds. Creeping juniper, a shrub frequently used on embankments, does not compete well with weeds. . Along tops of cut slopes and ridges use conn- erous species which require lillle supplemen- tal water. . Turf grasses should be varied to provide con- traslS in textures, colors and heights. De- sign should also Incorporate taller grasses in such a way that they can remain at full height, with only one mowing per season in lale lall aner seed has sel. . Bunch grasses should always be mixed with sod-forming grasses to provide adequate erosion conlrol and a more even visual ap- pearance. . Tall fescua will dominate when 1i1cluded In a turf mix used In an Irrfgated araa; other grasses In the mix will dominate In a non-Irrigated area. How. ever, tall fescue/smooth brome has proven to be a good mix for highway purposes. . Fairway crested wheatgrass is a bunch grass which outcompetes other grasses In non-Irrigated areas. This grass can be brought up to turf stan- dards wllh beller maintenance, Including heavier seeding and some supplemental irrigation. . Because 01 its dlsllncl/ve blue-green color, west- ern wheatgrass is ideal for color variallons or con- trasts. As an example, its color could serva as an Indicator or 'divider' for those turf areas to be left unmowed, However, western wheatgrass will be outcompeted " mixed with other turf grasses such as smooth brome and tall fescue because of its slow germination rate. PLANT PALETTE A plant palelle has been compiled as a reference tor plant material selecllon. The palelle lneludes Informallon concerning Irrigation and maintenance requirements, aesthellc characteristics, disadvan- tages and advantages 01 each speclas. 'rrlgation and maintenance requirements are ranked on a three point scale. The plant list is not all Inclusive and consultants have the opportunity to develop and submll their own list of plant material. All plant material must meet the overall projact goals, be ranked with a irrigation and maintenance level des- Ignation and must be approved by the Highway De- partment before Inclusion In the landscape plan. See Appendix B tor the Plant Palelte. 18.