The makings of deep mulch, sheet mulch and leaf mold
Call me a dirt perv, but few things are sexier to me than luscious, rich, fertile garden soil. When it comes time to plant next spring, this beautiful,weed-free soil is where you’d like to start, yes? Embrace the cycles of the season, get on Momma Nature’s team, and be ready to win.
As a permaculturist, my first mode of action is to observe natural cycles and mimic and enhance them to achieve my goals. As I look forward to next year’s plantings, a soil that is friable and free of weeds is a great place to start. By working with nature, I can achieve that goal with a minimum amount of work and purchased inputs.
Despite the fact that the trees have dropped their leaves and the perennials have gone dormant, there is a tremendous amount of activity going on under that layer of fallen organic matter. Where spring and summer are cycles of growth, late fall and winter are cycles of decay and regeneration. This is the season to transform the year’s plant growth into nutrients and humus for the following spring, and the billions of organisms in residency will eagerly go to work facilitating this process. The following techniques will help you get there.
Deep mulching
This technique is as simple as covering your garden soil with a thick layer of hay, straw or other mulch. This will facilitate a high level of activity in the duff, that point where the upper layer of soil meets the lowest point in the mulch layer. Here you’ll find the highest level of microbial activity, regardless of the season. In addition, the deep mulch will protect your soil from compaction due to the weight of heavy snow and errant roommates/pets/children. If you’ve planted garlic already, make sure to use this technique to keep it insulated and protected through winter.
The process: An effective layer of straw or hay is two to four inches; up to 12 inches is a boss move. For a bark mulch or coarse compost, two inches is great, four inches or more gets you extra credit.
Leaf mold
Leaf mold is partially decomposed mulch made from fallen leaves. This process invites mycelium to break down the lignin in leaf tissue, resulting in mulch rich in beneficial fungal biomass. Since most garden soils are lacking in fungal biomass, adding this mulch to your garden is quite useful if you are trying to remediate a garden ravaged by years of tilling. Finished leaf mold mulch is especially good when applied to trees and perennials.
If you constantly battle bindweed, then focusing on getting the fungal biomass up in your soil should be a priority. Since we are not adding any nitrogen-rich material (green material) to our pile, we intentionally avoid the thermophyllic composting process, so make sure that you only add leaves to your pile, no animal manures or weeds. This is not the same as making a traditional compost.
The process: As the name implies, the only ingredient is leaves from trees and shrubs. The more variety you can compile, the better. A pile at least four feet cubed is the minimum size for an optimum pile, but by all means, whatever you can get together is great. The keys to a successful leaf mold are proper moisture and aeration. Aim to keep the moisture like that of a wrung-out sponge, and fluff the pile occasionally to keep it light and airy. Perform this process directly on a garden bed or two for maximum benefit.
Sheet mulching
This is a staple of permaculture design and is used most often to simultaneously build soil while suppressing and killing weedy areas or lawns. Quite similar to “lasagna” composting, it is the process of layering cardboard and compostable materials so that they form an impenetrable layer to the weeds or lawn you are trying to get rid of. While the weeds or lawn are being smothered by the layer of cardboard, the layers above are a festival of microbial activity, actively breaking down the materials into soil. This is a great technique for expanding your garden into areas that are currently being wasted as lawn, or conquering that weedy, neglected area of a larger yard. Sheet mulch an area now, and you’ll have a garden bed ready to roll in spring.
The process: In the area to be sheet mulched, mow or trample any tall weeds, and spread a layer of manure down (half-inch to an inch). Moisten this (and every following layer) with water as you build it. Aim for the feel of a wrung-out sponge. Top this with a solid layer of cardboard, any seams generously overlapped. Then put down another half-inch or so of manure, followed by eight to 12 inches of mulch. A boss move from there is one to two inches of high-quality compost, done right so the weed seeds have been cooked out of viability. The worms will go bonkers for the cardboard, and this thick cake of compostables will eagerly progress into soil by spring.