The tomato, bean, zucchini, blueberry, etc. harvest is in full swing now — and so is the organic matter harvest. If you want to depend as little as possible on outside sources to add nutrients and organic matter to your soil, start saving…

Grass clippings — A mower that collects grass clippings can add an abundance of organic matter to your garden quickly. Each time you mow your lawn — assuming you don’t use toxic synthetic herbicides (weed killers) on it — put clippings on the soil as mulch around vegetable and ornamental plants. Put them on top of six or so sheets of black and white newspaper for maximum weed control in garden paths, or just spread an inch or two of clippings alone in paths for less long-lasting weed control but for added organic matter.

Don’t put grass clippings too close to crop plants, because if piled more than an inch or so deep, they can give off enough heat as they initially decompose to burn tender young plants. Also, don’t put them around bush bean plants, because they splash onto those low-hanging beans and are very hard to wash off.

If you don’t have a mower that collects clippings, you could rake them or, if you have a scythe, let some lawn grass grow tall, then cut it with the scythe and use that for mulch or compost.

Garden and kitchen refuse — Discarded onion leaves, tomato stems, melon rinds and other non-meat kitchen waste, as well as garden weeds, make great compost. I put these materials, along with soil clinging to the weeds (the soil inoculates the pile with organisms that decompose organic matter), in a barrel that my son mounted on a stand for me so that it’s easy to rotate. This rotating barrel, with holes drilled in it for aeration, makes turning compost very easy and really does speed production of quality compost. Getting the finished compost out can be a little tricky, but worth the effort.

Green manure crops — Farmers and gardeners often grow crops such as clover or alfalfa specifically to add organic matter and nutrients to soils. I have a patch of comfrey growing on our leach field that produces lush green growth that can be cut three times each summer. (Sometimes I get to it once or twice.) The comfrey tops can be added to compost piles to add nutrients, moisture and mucilage that speed the decomposition process. They can also be laid on top of newspaper or cardboard mulch, much like grass clippings — but somewhat messier. Comfrey should be grown only where the soil won’t be tilled or otherwise disturbed, ever, since the tiniest bit of root that is moved via tilling can spread the plant where it’s not wanted.

Fall leaves — Free for the taking! Collect leaves of deciduous trees when they fall in autumn. If you can collect them with a mower that shreds and bags them, they’ll make a perfect mulch to put on garden beds over winter, protecting the soil from eroding and adding nutrients from deep in the soil (where tree roots grew) to the vegetable beds as they decompose. Or just rake leaves and pile them in a bin made from chicken wire or other fencing to contain them (a 3-foot by 3-foot by 3-foot bin is good), let them sit, don’t let them dry out, and in a year or two you’ll have “leaf mold” — composted leaves. Mulch with the leaf mold or till it into the soil to improve soil structure, water-holding capacity and drainage.

These free sources of organic matter provide almost all the nutrition for our vegetable garden.