The quickest way to improve the health of your soil is to stop blowing your garden as if you were vacuuming your living room carpet.  Blowers are stripping the soil of nutrients and blowing the topsoil away.  Leaves should remain under plants, or be composted and returned to the beds later.  A thick layer of compost or mulch around plants will prevent evaporation and, as it rots down, will replenish the organic matter in the soil.  In the Los Angeles area, free mulch is available from several sites, see www.lacitysan.org/srpcd/mulch_giveaway.html.  Sometimes this free mulch will have small pieces of plastic or glass in it so be careful if you have children or pets.  Mulching will tidy up and unify the appearance of the garden at the same time as it provides insulating shelter for roots, worms, and necessary bugs. Mulch should not be piled up around the root crowns of trees because it can encourage destructive fungi to thrive.