Hi Margaret,
Congratulations on your venture!
Before I moved to the Hotchkiss/Paonia area (~5500') I lived on the front range west of Boulder at 9200'. To say that gardening was a challenge would be an understatement, but I did have some successes. I'm guessing that your weather will not be so extreme as to have a 60 day growing period and hurricane force winds in the winter!
Anyway, I had to deal with decomposed granite there, as well. If I had known about Hugelkultur then, I definitely would have used it! You will have to bring in materials for planting. I tried to dig down about 2' if I could, made raised beds of the plentiful rock , filled with topsoil, manure, and
compost, and always had a thick layer of
straw on everything. Our compost consisted of food waste and
chicken manure and bedding from our
chickens. I found niches among rock outcroppings and by the house where I made small growing areas for more frost-sensitive plants. I used row cover on nearly everything as my 60 day growing season was nearing its end. I had great success with a hoop house and a cold frame. My dear one built a tiny
greenhouse out of reclaimed materials, but I only got to use it one season. It was tricky because everything got too hot in there. I didn't have
enough time to tweak my methods with that.
For cultivated plants, I had pretty good success with seeds from high altitude gardens, and Botanical Interests. I also bought
native plants from the county extension's plant sale in the spring, and those usually survived.
The aspen will be great for your Hugelkultur, but it will break down quickly as it's a very soft wood. As for the weeds...they could be useful...even at 9200' I was surrounded with medicinal/edible plants!