Before you use any tree that you don't know well, first look around the base of the tree to see if other plants are growing there, if not, you might be looking at allopathy and that would mean you need to let those branches age for 1 to 2 years before you use them in a hugel type situation.
Clay soil can be changed with the use of compost teas and or fungal slurries, mushroom caps chopped in a blender with water then poured over the soil or over branches are good for starting up hyphae growth and consequently soil improvement.
Oak leaves combined with your manures and bedding materials will make a good compost, just add a fungal slurry as you are piling up your heap, don't forget that spent coffee grounds are great in a compost heap.
Keeping a heap moist but not wet is the key to making good compost.
Unfortunately, there is going to be a period of "back breaking" work but you should only have to do that part once, perhaps twice at the most.
It is one of the price we pay to make great soil.
So, make your manure rich composted oak leaves then spread them in a bed and mix with the soil that is there, you can do this step easier with a cement mixer and a tarp to dump it out on once mixed well.
Since it sounds like you already have raised beds, You would only dig the dirt contained in those beds to use for the above step.
If you want to add wood for the sponge effect, do that after you have removed the soil from the bed, pour on some mushroom slurry(all over the wood) then add back your composted manure/bed soil mix and you are ready to go.
From there, anytime you have spent coffee grounds, spread them on the surface of the garden bed(s) and if you decide to use oak leaves to make leaf mold, that does well for a mulch layer over the bed soil too.
Do you have a tractor? Im currently filling my new raised beds with it. Im scraping under the oak trees about an inch or 2 deep. This gives me some leaves with a lot of decomposed leaves. It looks great. Its not clumped like the dirt i get elsewhere on the property. If no tractor, it can be raked/shoveled easily. The oak leaves havent dropped yet, so ill get a new layer in my scraped areas soon to prevent erosion.
Im also strategically leaving the beds low. One bed was left 6" low. I planted potatoes 2" deep. Ill gradually keep filling it as the plants come up. It spreads the workload. I did the same with asparaugus.
i plant more blackberries and asparagus every year. When you think of perrenials(plant once, harvest for years), these are king in our location. Its only been one season, but i planted horseradish last year. Too early too tell if it will reestablish, but im hopeful.
Thank Everyone for your helpful tips!!! . I will dig under the leaves to get the composting ones. I will also make a compost tea out of aged chicken manure. I do not have any mushrooms. I plan to pour it over the dead wood to activate the composting. I have all these materials available but was not sure if they were safe to use. I am behind this year with so much unusually cold weather this winter for Texas and the extra work it brought on. ( Lots of extra feeding and breaking ice this year. ) I am seeing signs of green and am getting excited about my garden. I know I should have started earlier but this winter wore me out. Little by little I hope to decrease the work required before planting. 😃
I struggle with similar conditions in Central Oklahoma. And I refuse to buy soil, except for a tiny bit of potting soil when it goes on clearance in the fall.
As you already know, we can't just shovel up the local dirt into our raised beds, or it will bake into lifeless concrete cubes that are even worse than the native mineral ground. But I have found that it's impossible to get enough volume without using some local mineral dirt. So I have evolved a number of cheats. All of these are slow, evolutionary, multi-year processes.
When I build a new bed, I start by digging out the dirt in the bottom and throwing in as much old wood as I can, then putting the dirt back. Then I'll fill the bottom third of the bed with a mix of wood and mineral soil. Over years, this will settle down as the wood rots, which is why I always need to be adding stuff -- organic matter by preference, improved mineral soils more commonly.
I build my beds tall. This gets them up out of the zone where rats and rabbits and gophers and moles and voles are comfortable operating, and into the zone where weeds and pests fall comfortably under my eye and hand. (I'm tall and don't stoop easily.)
In the bottom half of the bed I'll put anything organic that grew on the property, I'm not fussy. I don't worry much about alleopathy, it strikes me as an overrated concern. I have a lot of Osage Orange trees, so the "horse apple" (woody grapefruit-sized fruits) they drop are particularly easy to collect by the hundreds of pounds; I use these a lot buried deep in my beds. (Too shallow and I would get seedlings.) Leaves, fresh or old. Forest duff. Twigs and sticks. Dead weeds. Brush hogging detritus. Anything. Mixed about fifty-fifty with the local clay-heavy "red dirt". As I get closer to my planting layer, I put more effort into going out deeper into the woods and breaking down old fallen hardwood trees, scraping up all the decomposed wood (the little cubes of dry rot) and the organic-rich matter around and under them. But that's hard work and there's never enough.
As a sort of compromise layer, I watch for gopher holes. Gophers do a great job of digging out a soft, sifted, aerated form of my local dirt. It does a much better job of filling containers and beds than anything I can dig myself. One good fresh gopher mound shovels into a five gallon bucket.
But all of that is the "hurry up" part of the project. Then there's the long game. I'm always wanting to plant something in a container for which I have no soil. Inevitably I sigh and "make do" -- which means, I take my container (usually a salvaged five gallon bucket) and fill the bottom half with fresh greens (weeds or leaves) and the top half with raw mineral dirt. I'll use a little compost or fertilizer or whatever I've got to feed whatever I plant into this doomed arrangement, then mulch heavily on top with fresh comfrey leaves. Then it will grow however it grows that season -- usually badly due to the lack of good soil in my container. But that's not the point. Over the growing season, I'll get enough soil life going to break down the green stuff at the bottom, eat my mulch, and shoot roots through the whole shebang. After my plant is done, I've got a bucket full of something that looks a lot more like "real soil" than the shovelfuls of mineral dirts I scooped into bucket originally. You couldn't (wouldn't want to) plant back into that bucket, but every winter I go around and tip all those makeshifts into the tops of my raised beds, which have all been settling. They usually come out as bucket-shaped chunks of hardness, which I have to whack apart with a garden tool, but when I do, it crumbles into crappy soil, not pure mineral dirt; there's organic matter in it now. It's not beautiful, but it's way better.
I do a similar thing with water chestnuts, which I grow everywhere in small containers full of raw dirt and water. They don't grow big enough to be worth eating if I don't give them good rich soil for starters, but they do absolutely convert red dirt into grey/black mucky organic-rich earth and root masses in a single growing season, while providing habitat for dragonflies and frogs. Then I dump those containers into the bottom or middle of my raised beds for next year. (They will send up weedy reeds if I use the root-filled masses too close to the surface of my beds.)
Try Jerry Baker tips for natural garden remedies you can add to your beds. Beer, baby shampoo other things can be added that you can buy at the dollar store to help your soil. I live in the high desert in California. I have similar conditions to yours, except droughts which is our norm. So I buy dollar store diapers, rip out the cotton and gel absorb lining and put it where I need to retain water. Where the roots will need to retain water longer. I use rolls of shade cloth when August comes for the real hot time.
Echoing some others: I fill my raised beds with alternating layers of mixed up leaves and composted steer manure. The leaves come free on the curb, nicely bagged for me. I'm consuming over 200 (!) Bags this year, and that's for a small yard. That will start to decompose over the winter, and then I do pay to make about 4" of high quality raised bed mix for the top in the spring.
I'm a ways North of you, but here's some thoughts that should still apply:
-Compost or mulch too heavy in oak leaves can be a problem. They're best in a mix. That plenty of manure you mentioned should do the trick!
-Magnolia, Mesquite, Cedar, Pecan and Walnut are all to varying degrees allelopathic, and may not play well with a garden. Especially the shells of pecans and walnuts. Buried under the garden wouldn't have the same effect necessarily, but
-Black Locust, Honey Locust, Catalpas and all of the above are pretty rot resistant, can take a long time to break down.
-Most of the Texas metros have services like Chipdrop, that take chipped wood from landscapers and deliver it to gardeners. I pay them $5 for the inconvenience of keeping out the above mentioned species and they bring me tons of mulch
-And speaking of: TONS of mulch. Even Spring and Winter gardens tend to dry out under the Texas sun, especially if you're in part of the hill country that still gets the full blast of the wind. Mulch helps, I hear some have had good luck with sunken beds, and something upwind to help break the wind (shrubs, corn, sunflowers, etc) can be a huge help. A little wind isn't bad of course, but this part of the state at least loves to flatten a garden.
-Mulch also helps with the 5-inches-of-rain-in-two-hours storms, and with hail season.
"The highest function of ecology is the understanding of consequences."
"Cultivate gratitude; hand out seed packets"
Fresh hugels will be attractive to rodents if you don't make sure to build them with no air spaces, even then you might find a few that decide to dig in to make a home.
Rodents are snake food, so it should be expected that snakes will come for a meal.
Usually the first year is the only "problem" year, then as the mound settles in the food animals will mostly go away and that means the snakes (if you have any) will follow their food supply and leave too.
I have three hugels, one is giant and that is the only one that has ever had snakes visit it, it is full of rabbit holes and because of them we don't even plant that mound, it has become populated with natural plants is now sort of a sanctuary for the local wild life.