After building and ronovating many landscapes in the desert I have started using a product call "Netafim" a drip line that can be arranged in a grid like pattern over the roots of established trees. I believe this would be very useful in the case of your Ash tree since a bubbler here or there or even numerous drip emitters placed at the base of the tree will not as easily give you the uniform coverage over the entire existing root system that I have seen so far with the "Netafim" systems. Although an established Ash tree is very tolerable of drought it is not a xerophyte and although the Netafim can help it would also be a good idea to incorporate an organic material over the roots. Even integrating lets say your flagstone.. some boulders and some larger sized rock with and organic surface would make soil conditions more tolerable for your Ash tree. Landscape fabric is alomost always if not always a waste of time and money and I have not used it in over 15 years but I manage xeriscapes that have acres of drought landscapes. Weeds will still grow .. and the fabric will work it's way to the surface and haunt you .. plus "good fabrics" .. there are not any ...cost as much as sod. Take out the grass carefully without undo damage to the tree roots don't simply cover it. Roses for example are another plant that would do best with an organic base and not surrounded by rock mulch. If you are going to add a rock mulch to your landscape know thy plants and have a thought out reason why you are using rock and do not mindlessly add rock as some have covered the desert with grass. A preemergent .. maybe .. What for ?? What weeds ? If you are redoing the landscape get rid of as much old irrigation as you can .. old pipes and old valves should best be replaced. Less aggravation in the long run... http://www.netafim-usa.com/ Good Day ....

I'm not a landscape architect or a landscaper --- just a homeowner/gardener ---- but those photos scare me too. Kind of reminds me of the dropped backyard in my first house. All the land slopes down to your windows and the open garage. I don't know what kind of underground drainage system you have, but it does look like the front lawn is higher than the back lawn. That's worrisome because it could mean the lowest part of your property is where the house was placed. And the fact that the water level of the pond is higher than the basement windows is another red flag. I'm guessing that the drainage from your downspouts and any runoff goes into those drains outside the windows? If that were my house, I would not landscape on those slopes. Anything you plant there will need to be watered, which would only cause more water to flow down the hills. I agree that some kind of hardscape work is needed instead. Is it possible to have a walled patio area in front of the windows and the open garage? Believe me when I tell you this --- water table levels can change in a neighborhood and builders can do some crazy things! In my old neighborhood, a builder put up a house in on a wet lot that was below the road level. There was a trickling steam that ran across the lot and down to a river. We watched as the basement floor was poured on the earth and the foundation walls were cemented sraight UP from the ground. Then the builder mapped out the septic field by marking about 10/12 feet up on the trunks of trees! (no lie) He hauled in 'dirt' (lots of sand) to raise up the ground to the level of the road. Granted, this was 30 years ago in a small town, but geez! We often wondered when those streams would decide to percolate up into the basement. Water can do some crazy things. Molie

Thank you for the suggestions on layout and plant types. I would love to put in all of those plants! I've never planted anything in my backyard before and wonder what type of amendments I would need to put into the soil prior to planting, and how to correctly apply the amendments. There's a lot of information when I research and my brain is having trouble ciphering what my next move should be. I can't dig very deep holes because it might shift the dirt too much on the slopes.

I suggest you post this in the California Gardening forum for the best localized input. Conditions in CA with regard to the drought, fire concerns and invasive species makes it somewhat tricky for outsiders to make meaningful comments. I would also suggest you take a close look at the California Friendly gardening program, which is statewide, promotes all 3 of the previously listed concerns and even pays out rebates for converting one's garden into a more environmentally friendly landscape.