he best fertilizer you will never have to buy is Autumn leaves. Leaves are high in phosphorus, potassium and carbs which are very important for plants to be healthy.
For those of us who work nutritionally, the five most important nutrients for healthy plants is: Nitrogen, Phosphorus, Potassium, Calcium and Carbs. Leaves has three out of five! Just add lime and gypsum for calcium and green grass clippings for nitrogen and you will have some very happy plants next year.
Chop the leaves with a lawn mower because the smaller the pieces the faster they break down. I go over and over the pile of leaves until the pieces are fingernail sized. Then I rake them up and add them to the beds
I buy my lime and gypsum at Home Depot or Menards. A 40 pound bag costs $5.
Gypsum is important because it contains sulfur. Sulfur is needed to begin the compost process.Microbes use sulfur to make compost. If the microbes don't find any sulfur then the carbon digested from the leaves is released as CO2 gas and goes into the atmosphere. So sulfur is very important. Gypsum is calcium sulfate quickly and is available to the microbes and plants.
Microbes require a high calcium environment so I always add some lime together with my gypsum. The two work together very well and make good results in the soil.
Leaf mulch makes plants very happy so save your leaves every year and grab your neighbors leaves too if he bags them or dumps them near the road.