The thickness of the wall matches the width of standard 2 x 4 lumber, so I don't have to cut lumber for a piece to put at the end of the forms. The tie bolts do go through the wall, actually I often use all-thread cut to length instead of bolts. Inside the forms, 3/4 inch pvc pipe acts as a spacer to set the wall thickness. The bolts run through the pvc spacers which protect them from the concrete (see photo below). I coat the pvc spacers with full strength mop-n-glo and let it dry before form assembly. After the pour, remove panels, bolts, and spacers to be used on the next wall section. For these little bed walls up to 12 inches high, I don't pour a footer. I level the soil to the bottom of the wall grade then about every 4 feet along the wall I dig a post hole a minimum of 1 ft deep plus an additional inch for each inch of wall height above 4 inches. The post hole is filled with concrete and a rebar inserted to extend upward into where the wall will be built.

Bboy, those maps were obviously drawn up with all the seismic lines taken into consideration. Sorry. Bad joke- bad, bad joke. God, don't strike me down. Seriously, microclimates DO exist EVERYWHERE- like the South facing side of my brick home where I grow my Loquat, but I do know that the terrain out West is very diverse. Hope to see it in person some day. Most shrubs sold at a nursery though should be suitable for planting in the not too distant vicinity of the nursery's location WITHOUT the artifical extra heat of a brick home's exterior. I'm not saying I don't ever shop at the Big Box stores, but I've really stopped expecting them to get much of anything right. There is NO replacement for a gardener's own behind the scenes research- however, I view the knowledge of the staff as a major indication of a nursery's reputabilty. You ought to know what you sell by in large. Sure, you may have a few grunts loading and unloading things off of a truck or people who have just begun to get their feet wet, but there should be SOMEONE present who has some idea of the plant you are asking about or has the ability to summons someone else who does ASAP. They should also have good reference books ON HAND because, obviously, no one can know everything. And I don't think I'm a snob about latin names, but if I go to A NURSERY and the person in charge of shrubs doesn't know what "Prunus laurocerasus" is when they've been selling "Cherry Laurels" for years, I will be extremely leery and take any info I gather there with half a grain of salt. I've been shocked by nursery owners who obviously couldn't explain the difference between a genus, a species and a cultivar if they had to. Not that I've ever directly asked someone to do so- I never set out to embarass someone, but I will find subtle ways of "testing the water" if I wind up at a strange nursery and feel like maybe gambling on a plant that I am less familiar with.

A 100% slope is actually 1:1 or a 45deg slope, but I have donned my rappelling gear and planted on vertical faces. Yes, the mulch will have to be replenished from time to time. I wish I could tell you how often but there are some variables. I also can't tell you costs because I don't know about either your plant or labor market. You can also get mulch for cheap or free from tree trimmers and some municipalities offer free composted mulch from green bins. You will also have to weed regardless, but the mulch makes it easier. Aggressive groundcover can itself become a weed, especially if it self sows. Plus, weeds are by their nature aggressive and can compete with a lot of aggressive groundcovers, at least for a little while. When I say shrubs, they can be groundcovers as well. They are just low growing shrubs. You can also mulch heavily (8-12") and sow perennial shrub seed. That is a proven restoration technique, although weeds will still come up. Since you are new to gardening, I will recommend this site, The Informed Gardener, especialy the bits about mulch.

It's extremely counter-intuitive, but a layer of gravel or other coarse material does not improve drainage either in a pot or just below a planting mix in a bed. (At the subgrade base of a retaining wall, with or without drain pipe is another case entirely.) Water has considerable difficulty moving either vertically or horizontally from a mix composed of smaller particles to one with large particles and a much greater percentage of air spaces. The phenomenon is called "perching" and there are many technical explanations online as well as a good discussion of the issue on the container growing portion of Garden Web. Even though rhododendrons are indeed shallow rooted plants, what can happen is this: With a gravel layer say 8 to 10 inches below the planting mix the lower few inches of that mix becomes saturated. Capillary action can cause the entire depth of planting mix to reach a saturated state before it begins to give up water to the gravel layer. Shallow azalea pots ,btw, are not intended for long tem growth. They're a florist convention for quick growing azaleas having more to do with aesthetics, tradition, weight,etc.than with long term growth of the plant. That's why they are very rarely used by commercial rhododendron operations which need to grow on their plants for a number of years before they can be marketed.