Since you're already experienced with native gardening and have sun exposure, it should do well in your planned area

Well half of this area above the driveway brick wall is a semi empty garden and half is an area of decomposed granite over road rock like they use on the city park trails. It is a small area we never use. The garden dirt will have to be leveled out over the granite except a seating area that I will repurpose saved concrete tiles for as the rest will be primarily a play area. I’ve read you can leave the granite as it’s been tamped down, been there for a while, and permeable so soil can go down over it and then plant grass on top of it but how deep would the soil need to be? There are drains in there as that part is above a walkway with a stone lined wall about 12ft. from the side of our house. They take the water way away. The rest of the dirt is in front. I would probably mark, raise and keep the drains there at ground level to be safe. There has never been a problem with water in the rest. Just needs a rock wall around some of it. All the watering filters and valves are already covered and on that side for irrigation! I read it uses far less water. It’s the logistics but I think it could be a pretty decent sized yet cozy play area. It’s always iffy changing topography when you don’t know what might come off of your neighbor’s yard or how moving dirt might change things🤞🏻

A picture would be worth a few thousand more words.

I'm reasonably certain buffalo grass will grow right into the decomposed granite. This means you will not have to bring in more soil. Adding more soil will change the drainage, and that is almost never a great idea. Adding soil is beyond iffy. The previous owners of our current house created a moat by adding 1/4" of topsoil every few years...for 50 years. Adding topsoil will change your drainage patterns. If you don't absolutely need it, don't do it. Rich garden soil is not the natural habitat of buffalo grass to begin with. But you might ask the supplier of your UC Verde if it will do well in decomposed granite. The new grass roots should loosen the granite somewhat and allow air and water passage as the roots will need. Since the granite has few nutrients available I would put down a dose of organic fertilizer at planting time or before. Once you have full coverage with the grass, an application of compost will help to insert otherwise missing organic matter (microbes) into the granite. After that one app of compost you should not need more compost. Organic fertilizer will keep the microbe population happy. Apply the organic fertilizer on or about the major federal holidays (Washington's Birthday, Memorial Day, 4th of July, Labor Day, Thanksgiving) to keep it green, dense, and growing.

My favorite organic fertilizer is alfalfa pellets (rabbit chow) from the local feed store (where horse tack and feed are sold). Alfalfa pellets are often a main ingredient in commercially bagged organic fertilizers, and you can save a bundle buying it by itself in unmarked bags. Also soybean meal, cornmeal, and corn gluten meal make excellent fertilizers. Ordinary cornmeal is not as powerful with Nitrogen, but it has other qualities that make it good.

Grasses typically shed some of their roots every year, so eventually your soil will build up more organic material by itself.

Also, this forum could really use some first hand experience with UC Verde. I've never seen the stuff, but I've seen other excellent hybrid buffalo grass. UC Verde seems to be the best, by far, of the available hybrids. Before and after pictures would be wonderful!

Wow. You made my day! I know exactly the place to get those pellets. This will be my first experience with grass of this type. I will have the top of the existing dirt area removed in front leaving an area planted along the driveway, level out the area to the d.granite and extend the rock wall protecting the older JMaples, and others I planted years ago along the border per the photos It will be fascinating to compare the grass that grows in the dirt part to the grass that grows in the granite part. Below are photos of the areas I planted over the years, the first being the area in question from the driveway, the second from our front patio, part of the walkway to be removed and the third the granite part. Other than some lavender and poppies I just removed I essentially let most of the area behind the walkway go to put in the grass on the back side of it. There were lots of annual natives now gone to seed. Thanks. 🤞🏻

So here are the before photos. I love the Pittosporum Eugenoides verigata between the Matsubusa J Maples. I planted those about 25? Years ago? They will remain.

WOW! You made MY day! Reminds me of Butchart Gardens in Canada.

It will be very interesting to see how the grass does on the two different soils. I hope you keep us updated.

For a little more motivation on the alfalfa pellets, here is a picture posted on this forum in 2011 by mrmumbles. He started with his unfertilized zoysia lawn in mid May. He dropped a handful of alfalfa pellets and took the picture in mid June.

You can clearly see the improved color, density, and growth. This picture has sold a lot of rabbit chow over the years.

A tiny replica! Ha. Been there. What a compliment. My native gully with boulders is the amazing thing. We now have 43 species of birds on the property including a Great Horned owl pair. I took a photo of their owlet in a bay tree below and a parent in an oak tree in back off the deck among others looking down at us with disdain in the daytime!!!! Unafraid. When I came up from under our family room window with binoculars looking straight into its eyes it had enough and moved next door! Ha. They fly back and forth between our trees and now we have black vultures below per usual below. Birds, bees and butterflies are my passion. Hence the horticulture over the years.
What you showed is amazing. I’m very excited to try this. Will talk to the UC Verde people about the situation. I mean other weeds grew there so that makes perfect sense and I love the fertilizer idea. We’ve been in our home 40 years! Once again thanks.

The little town we used to live in had a major vulture population. Look closely at the water tower supports.

Aiyiyi. I think these come in because of the creek which is like the Russian River in winter and gently moves in summer from the drainage uphill. I think ours feast on what the hawks and owls leave. I found a pile of feathers and bones. Do they stay or migrate? These leave after a while.

SO after research I find that our deer will eat the buffalo grass-of course-so I may extend our decomposed granite the entire way. However, I’ve been considering doing a plot of it at the front end to see how it does. The only alternative is fencing which might look dumb unless I design it well, like an open curve in front in iron $$$ and a heavy Benner deer fence system with removable posts along the sides and back. I’m doing that around my hillside monarch garden. Kind of goes against my nature. None of us have fenced in property except for here and there right around the homes. There really is ample room for the deer I love to eat my other plants! 😀 There is a deer trail or two between our property. Really except for a few I told my neighbor were “deer food” when he asked, seriously, they touch few natives with choice European plants around the neighborhood. I leave a huge English Laurel in back for them to munch on. Plan to create a “Deer Food” sign for it. The occasional buck lays down next to it like my all time favorite buck. Gone. Most likely hit by a car or the wasting disease going around but I digress….

Here he is now was.