So-- a couple years ago this small area was part of a chicken coop. We gave up on it eventually because of the (tail less!) racoon that was gutting the chickens. Plus, I was getting lazy. I used some of our compost pile (dirt, clippings, raw fruit and vegetable waste, egg shells, coffee grounds, etc.) and mixed it with the existing soil- that's it. The plants were bought from a small native plant nursery. I try to stick to straight species whenever possible, but sometimes only a few hybrid "nativars" are available. When fall rolled around, the leaves on our gradually shrinking lawn were collected in a bag with the mulching mower and spread over this new small bed situated in dappled shade. I allow a few dandelions to grow in the early spring for the bees, since it's one of the first things to flower and feed them. I dig them out in the summertime.
Leaves are valuable mulch for the gardens because:
1.) it suppresses the weeds
2.) increases the fertility of the soil naturally as it decomposes.
3.) it holds in the moisture and balances temperatures in both summer and winter.
4.) it's FREE!