Frankly I have no idea how to advise you. Many who read this Forum become upset when someone suggests hiring a professional for an hour's consultation. In your situation I feel it is imperative to work with someone with local knowlege. First off, sedimentary limestone suggests that your sparse soil has a high pH resulting in a difficult growing situation. Probably raised planting beds/berms constructed of good top soil will be necessary. And how one goes about designing for ever present rattlesnakes really needs the know-how of a local. You have posed an interesting design problem, one with which few of us are familiar. Sorry that I can not be of more help.

My thoughts were along the line of nandina's. It would be very hard for me to comment on specifics because you have basically a large blank slate in an environment that I am completely unfamiliar with. There might be a regional forum where you could get some advice.

I would say that I would not just clear out the "brush and weeds" without having a general plan. Otherwise you will have this huge empty area to try and maintain. It may be that keeping a portion of this area natural looking is your best option.

- Brent

I think that you have a great opportunity to create someting great in a few years. I would start small and develop a plan for the area close to the house. Focus on native plants (develop a relationship with a local nursery)because they will grow without supplemental watering and fertilization. With your small plan, start thinking how you would like to enjoy the large area. ie. look at from the house, wander around in, recreation, etc.
You can keep the area natural while you make some paths in accordance with your plan. Step by step you can develop garden/plantings at destinations along the paths that will add interest to the landscape and compliment the overall natural setting. You will learn from the successes and failures but the failures will be small and not impact your overall plan.
I would avoid doing anything drastic to the status quo such as major clearing because you may bring on problems such as erosion and nothing will grow. You would then have a wasteland for years to come.
If snakes are a big concern, consult locals.

Stevega gave you some good advice - move slowly, and learn about Central Texas gardening before you do anything major. It's more than just a rather dry area - most of Central Texas is dealing with long-term drought, so natural landscaping where the soil is shallow just makes sense.

Have you been to the Ladybird Johnson Wildflower Center yet? There are demonstration gardens as well as other resources for Hill Country gardeners.

There's also a Texas forum right here on GardenWeb, and several of the regular contibuters live and garden in similar situations - they may even have rattlesnakes!

Annie in Austin

Here is a link that might be useful: WIldflower Center

Annie, I'm in Austin too. Where in central Tx do you live, ant777? I can suggest several nurseries that can help you if you live in this area. this is a really tough design problem and you will need professional help.

Jenny

All I see of the site is rock and a slope, no house, no budget, so it's unlikely what I have to say will be of use to you.

If the property were mine, the first thing I would do is study the rock formation. I would go to nearby areas where the rock was cut away, like in major road cuts. Was the cut made with explosivies? Did the rock fracture in layers or huge blocky shapes.

Then I would locate a shape of about 1600 to 2000 sq ft on the slope such that the start of the cut would be slightly above the present back of house grade. It would extend back into the slope on a flat grade to a point where the depth of cut would be about 7 to 8 feet.

Going by my study of road cuts I would use explosive experts, a trackhoe with a rock tooth and or a hammer, to make the rough excavation as shown below.

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An area about 15 ft square in the center would worked to almost flat with the slope running toward the house. Around the edge the cut would be a little deeper so drainage could be installed for the area. At the back of the cut, a small spot would be cut deeper for a pond with a waterfall down the rock face into it.

With the exceptions for the flat area and pond /drainage cuts, the rest of the cut would be left uneven bedrock sticking up around the site.

The larger rock taken from the cut would be stacked to either side of the entrance to form a retaining wall and backfilled with soil to support plant growth. Some of the rock could be used in the cut area to form raised beds for plants in the cut area.

Dress-out of the form would be to the house style with plants that fit the climate.

A nice river/waterfall/pond would look great. That is where I would start; in the first picture on the left hand side next to the tree by the fence.

As Stevega points out, you need to decide first what your family wants to do in the backyard, before you go to any professional. You can certainly drive around the neighborhood, look at municipal gardens, etc., and do some research into what grows well there. But before you ask a pro to spend time with you, you need to have established some parameters in your design. No one else can do this part for you. Would you sit and have breakfast on a patio? Relax in the evenings after work in a hammock? Practice putts on the weekend on your own mini-green? Think about how the seasonal weather will affect all activities -- too hot in the summer to go out; too cold or rainy in the winter? If bugs are a problem - anything from fire ants to wasps or mosquitos - how would you solve it? How much time/interest do you have to maintain landscaping, from weeding to pruning to watering? Have you established your budget, since an average cost for landscaping is 10% of the value of your property (here in CA it's higher, but labor is very costly)? Does the property have sufficient drainage or will you need to put it in?

If you have drought conditions, putting in a water feature, no matter how attractive, doesn't seem very practical. It is always better to garden WITH your environment, not against it. The research you do now will pay off in the design and implementation of a yard (e.g., not only garden plants but hardscape for your use) suitable to your local conditions and lifestyle. You definitely need local advice on this one. Anything you put in needs a sensible irrigation system of either drip emitters or soaker hoses. Anything else is a major water waster, and there's no point in installing something that can't be maintained in the long term.

This doesn't necessarily mean it has to be all cacti and sedum, just that you can plan ahead for both a nice yard and sensible maintenance. It's cooler in summer where I am, but we get no rain for six months in the summer, every year. We have a lush cottage garden, complete with citrus trees, of 2500 sq. ft. (total gardening area) that costs less than $20/mo in summer (May-Oct) water bills - water is expensive where we are, plus there's an upcharge for piping it up to homes on the hills. I never water more than once a week and can usually go 2-3 weeks without watering. I replaced the original soil and every year mulch heavily, because after doing some research I knew those two things would help the most.

Plants are living things and will force changes on you. Some will thrive and others will just.....die. You want to integrate your outside yard with your inside home, to get the most use and pleasure out of it. You need to plan your yard just as if you were planning an addition to your home, except that you don't need to add a ceiling!

Good luck with your yard.