When we pull harvest from the garden, week after week, we are taking from the garden ecosystem. We are taking from the soil.
Here in Southern California, where we can harvest year-round (with a seasonally-appropriate crop mix), that means we are taking from the soil constantly. In order to maintain basic soil fertility, we must always be building-building-building up our soil.
That means compost, it means mulch, it means worm castings, it means doing all the things that cultivate rich, alive, healthy organic garden soil.
Here are some resources we mentioned during the Jan 10 class:
“Feed your soil. Your soil feeds your plants, and your plants feed you.” (paraphrasing John Jeavons)
Feed your soil organisms. They are the ones who feed your plants (according to Lowenfels), and your plants feed you!
Think of yourself as being a “worm farmer” with the goal of growing bountiful soil life.
“Living soil” means an entire ecosystem of organisms – eating, pooping, reproducing, and interacting with all the other species. So you can’t just go to a garden center and buy a carton of “earthworms,” dump it in, and call it done.
For anything you might consider adding to the garden, ask yourself “what will this do for the soil critters? how can I benefit them?” The answer will guide you to best practices.
things that used to be plants.
Food for your soil critters
Fine-textured, mostly decomposed. mostly, you can’t tell what it used to be.
if you have Bermuda grass in your garden, there is no question. You must remove the Bermuda, which unfortunately means you must disturb your soil. How do you get rid of Bermuda grass?
if your garden is (miraculously) Bermuda-grass-free, you have the option of trying no-till. To do this, layer additions of compost on top of your existing garden soil. The larger organisms within the soil life – such as earthworms – will do the tilling for you. (trust them)
Protection for your soil critters, plus long-term food supply.
Coarse-textured, not decomposed. Examples: wood chips, straw, shredded paper.
layer on top of your soil, like “putting a quilt on your bed”
pine needles – in Southern California we don’t need to worry about the acidity, in fact we need it
colored mulch (bagged) from the Big Box Stores. Who knows what chemical treatments lurk within.
hay (animal feed) sold by animal supply store – will likely decompose quickly and have too many seeds.
wood chips that are all-eucalyptus – may have too many allelopathic oils and prevent plants from growing. However in 11 yrs of experience at the Community Garden at Holy Nativity, a bit of eucalyptus in a mix of other mulch chips isn’t harmful.
sources with mixed review:
“free mulch” from city – okay for pathways in ornamental gardens, but not recommended for food gardens.
redwood mulch (bagged at garden center). In my observation it seems to discourage seedlings from sprouting. (my guess is it’s allelopathic) It has worked fine for me around transplants and around pre-existing perennials and trees
grass clippings – if you cut grass before the seedheads form, it might serve as a good mulch. As the cut grass dries out, make sure it doesn’t mat up and form a barrier so that water can’t get to the soil (fluff the drying grass with a garden tool). if your grass is forming seedheads when you cut it, send it to the green bin to avoid compounding a weed problem.
non-organic materials, such as plastic, tire rubber, rocks, “landscape fabric”, etc. – some heat up (detrimental to soil life). some form a water barrier (detrimental to soil life). inorganic materials don’t decompose, thus they do not offer a long-term food supply for soil life
carbonaceous or not?
Lowenfels & Lewis teach us that trees and perennials crave carbonaceous mulch like wood chips. For annuals like vegetables, use the more-easily-broken-down mulches, like straw, leaves, paper.
green mulch, cover cropping
the term “green mulch” is often used for the practice of growing beneficial plants in between areas – for instance growing clover between rows of fruit trees, where the clover is periodically cut and left to decompose. It isn’t really something that fits into urban gardening practices.
the term “cover cropping” refers to the practice of growing restorative plants on a bed that is fallow, or not-being-used. If you are skipping a season (for instance you only grow vegetables in the summer season) you should consider growing legumes or clover as a cover crop when your garden is out-of-use.
great cover crops for Southern California’s cool season: peas, fava beans, clover, buckwheat
Geologic “soil shed”
the basic “bones” of your garden
Zoom out on Google maps: what are the massive, geologic-scale, pre-existing (and unalterable) conditions within which your garden exists? (river bottom, sand dune, beach, ancient riverbottom/sandstone, volcano, glacial deposit)
Starting a New Garden – here’s what we did with “virgin soil” to jump-start the Community Garden at Holy Nativity the very first year. (Once your garden is established, you don’t have to do these things)