Hi Clark and Welcome.
Ask a question and you will get a lot of different answers here.... and they're all good. What works in one place doesn't always work in another so you have to experiment.
Leaves? Leaves are Awesome! I wouldn't have any garden here without leaves! I beg people for their fall leaves and even post on Craiglist asking for un-sprayed, organic leaves. You can see pictures of what leaves have done for my gardens in the Permaculture forum.
They are great in compost which needs brown stuff (carbon) and green stuff to break them down (nitrogen). Leaves are almost my only source of brown stuff.
For many years I used to dig them into the beds for the winter, adding carbon. I figured there was still enough fertilizer (nitrogen) left over from summer to help them break down. But they break down like tissue paper and soon disappeared. [Special note- they won't break down at all if they are water logged]. Worked O.K. But there are much better uses for them.
So, every fall I start out with 2 big piles which I will put to good use all year. I never have enough. When I've used most of them and gotten down to the bottom of the piles it has composted into rich, black soil that is full of worms! Worms love leaves and are usually great for your garden. And I use that special soil to help any plants that have been struggling and as part of my mix to start seeds in. It works great!
I use leaves to mulch around all of my fruit trees. It keeps the roots cooler, holds more moisture, brings worms and breaks down into great soil. Most plants generally need some water, fertilizer and a regular supply of carbon over the years. And most people forget the carbon.
To grow great plants we need lots of good bacteria and fungi and I need to try to keep them alive and thriving all year long. That happens easily when I'm actively growing stuff there or if I've left lots of roots there to decompose which isn't always possible. The next best thing is to cover the beds with leaves in the off season which spawn lots of good molds and mycellium, feeds the bacteria and invites the worms. Good stuff.
It used to be hard to get seeds for my root crops like carrots, beets etc to germinate because they lay very close to the surface of the soil and quickly dry out. Now I sprinkle a thin layer of shredded leaves over the top and it keeps in enough moisture to give them the chance that they need.
Flip side... I do have to move aside a lot of the leaves from my beds when I have vegies growing. Too many bugs live under them in the summer and they love my vegies. Anyway, I could probably think of a dozen more reasons to have leaves but I have seeds to plant now. Happy gardening.
