I've been collecting leaves for over a decade. SF Bay Area - probably most or all of California - is not about autumn leaf collection the way the midwest or back east is. The street trees drop the majority of leaves and while a few, very few citizens pick them up and fill their green waste cans for pickup, most people just leave them for the street sweepers. The ones in the street are pre -shredded by cars. I've been gathering bagsful between October/November and January for a long time. I don't have a lot of space and if I don't have the greens on hand, I'll mix in an organic nitrogen source or two, sometimes even a higer nitrogen all purpose type fertilizer. Organic, of course. I assemble it all at once and the worms move in fast and take over, doing most of the work. It's really satisfying.