There are many, many California natives used for landscaping along freeways here. Coast Redwoods are ubiquitous, Pinus radiata, contorta and Cupressus macrocarpa are also used here in the Bay Area. Large native shrubs incude various Arctostaphylos, Ceanothus, Fremontodendron, Heteromeles arbutifolia are also fairly common. More California natives aren't used because many such as species Arctostaphylos and Ceanothus are not particularly long lived or smog resistant, or highly adaptable across multiple microclimates. There are plenty more large shrub/small tree species that could be used, such as Cercis, Calycanthus, Myrica, etc.

tinan, I doubt that noise is as easily abated by plantings as you may think. CALTRANS engineers are experts and even they have a hard time abating sound. Sometimes sound-deflecting walls are built only to find the sound, instead of being deflected upwards, goes in unexpected directions and creates headaches for another neighborhood which previously had no problems at all. Land topography has more impact on noise deflection than anything else. If you walk along the Bodega Head trail, at certain sections the ocean noise is thunderous; yet 50' away without any change except for a shift 10' inland and a protruding cliffside edge, the wave noise drops by two-thirds. No trees or level change are involved at all; it is all topographic noise deflection. Take a side path below cliff level and suddenly you can't hear any ocean noise, everything is silent. Certainly trees "en masse" will deflect noise. But you'd have to own a half-acre lot to plant enough trees to mass thickly enough to create a viable deflection wall on a level property. Walk around a freeway underpass, and you'll probably find that in certain spots almost underneath the freeway (it needs to be solid, not the type with separate roadways) the car noises stop. Sometimes they merge into a deep booming noise that is more pressure than noise, a rather odd feeling. All of us live in a geographically hilly area. This means that cell phone reception gives carriers nightmares and that noise from our maze of freeways travels upwards and outwards in a variety of directions, funneled by geography and climate. I can occasionally hear train whistles from the Amtrak lines two miles west - but not always, only at certain times. If sound were a simple thing, I would ALWAYS be able to hear them - the tracks don't move, and neither does my house (unless there's a rupture in the Hayward Fault, LOL). But I can't, even though I know that the trains blow their whistles at the same crossing twenty times a day.

"I like to believe that each person can decide for themselves whether or not a plant in a given situation is threatened to a point that it would be more beneficial to move it than to leave it where it stands, whether it is in a park or on a roadside or any public property. " A roadside is not punblic property. I think it would be of interest that in many cases when only a single individual of a plant species exists that plant is left as undisturbed as possible and is propegated instead of moved, because even then moving the plant is not more beneficial (indeed, probably worse) to leavin it. Those singular individual plants in question are not, however ignored. By looking at that example, NO plant is 'threatened to a point that it would be more beneficial to move it than to leave it where it stands' unless imminent destruction in the near future is likely due to human activites. Therefore in almost any surcumstances leaving the plants is definatly the better option, but some site care such as checking and removing all weeds in the vicinity of the plants is vastly better than moving them. Also, if you cant do that site maitence (for example, not on your land)your probably not supposed to be moving plants from there anyway. Unless you have premission of course, preferably permission to maintain the site. A roadside planting is most likely secure, and with the wildflowers and garlic mustard, perirodic weeding in the imidiate vicinity of the plant population may be all that is required for the long-term presistance of that population. It is interesting to note that in certain curcumstances (for example, native wild plants transplanted to a neatly kept garden) the population of transplanted plants are unlikely to survive in the long-term because they may not reproduce. While the individual transplanted plants may survive, the establishment and long-term presistance of a self-supporting population in in doubt, altough it can and does happen, it might just as easily not because of many subtle variables affecting the growing site means establishment of said transplanted plants might be in unlikely. Without long-term presistance of a self-supporting population, it, in my mind atleast, not a resce in the sence that these plants have been removed from a population that probably needs all the individuals it it can get, and presistance in the wild is far more important, ecologicly speaking, than presistance in cultivation. Note: the terms Establishment and self-supporting population does not just mean that the species sometimes reseeds itself, altough that is a important factor in the process. In the case of this garlic mustard weeding within the viicinity of the plants on a regular basis would probably ensure theri survival in the short term, altough their long-term survival may be in doubt because, lets face it, you wont be there forever to weed. WHat might work is if you suceed in reducing garlic mustards population density in the area.

Oh no!! You said the "T" word......topping. In the wrong hands this word can lead to permanently damaged landscape plants, especially trees. You could agressively trim, but why go to all that trouble? Just choose plants whose mature size will fit into your space and save your free time to enjoy your pool and landscape. As for vines, there are several to choose from. Forget wisteria here, but perhaps Lilac Vine (Hardenbergia violacea) would work. Lady Banks rose (thornless in white or yellow) grows fast as does Pink Trumpet Vine (Podranea ricasoliana). You don't want Bougainvillea with your pool or you'll be constantly fishing out the colorful leaves/flowers. Heres a link to Landscape Plants for the Arizona Desert which has over 200 low water use plants with photos and descriptions. You'll need to water your new plants correctly for the first few weeks so refer to page 14 of Landscape Watering by the Numbers. Page 9 shows how much water to apply based on the size of the plant. Most of the valley cities have free landscape classes offered by their water conservation offices. Of course folks on this forum always have great advice. Good luck!