Over the years, farmers and gardeners have noticed
that soil gains a bit of fertility when it is covered up--even by something that has no nutrients, like snow or plastic. Why? Nobody knows! But you
don't have to understand it to profit from it. Any mulch will give a slight increase in fertility, reduce soil compaction, reduce soil loss from rain or wind, and reduce the number of weeds. If you have nothing better, flattened cardboard boxes will do all of the above and feed earthworms as well. (We do not recommend plastic.)
Of course, if the cover is a mulch of organic matter, the effect is
much, much greater, because of all the nutrients released by the mulch. It starts an upward spiral, because the mulch feeds earthworms, who make tunnels--which brings oxygen deeper into the soil so that even more life can thrive and build even more fertility! So straw, lawn clippings, or leaves build richer soil, even in winter.
Only recently have we realized how leaves and branches feed the soil. If you have access to leaves, there is no better mulch to prevent weeds, feed earthworms, and build fertility. Research in Canada has shown that chipped branches and twigs--called ramial wood--has many more nutrients than trunk wood. Far from being "waste", this ramial provides food for the fungi and bacteria that make rich soil. It is also a great, easy-to-use weed-smothering mulch. (It should not be tilled in. Underground, oxygen is not available. It may be pulled aside or mixed into the top inch or two at planting time.) This research used leafless branches, so winter is a great time to get them. Since branches are the very part that most tree services, county road crews, and telephone companies are wanting to get rid of, there is a vast amount available, often for free. Just ask your city, county, telephone company, and private tree services if they have excess wood chips. Some tree services will come and dump them on your driveway.
This tip is excerpted from a longer article in our How-to section.
This work by Bountiful Gardens is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.