Suppress Garden Weeds with Cow-Manure Mulch

article image
Photo by Anuttama Budd
To plant seeds in a matted area, I make a groove in the mat with an edging tool and fill the groove with moist peat moss mixed with seeds. I water the peated area until the sprouted plants’ roots have reached the soil under the mat.

When we moved to our new farm five years ago, my husband Billy and I were thrilled to have rich, dark, volcanic soil after years of fighting to grow food and flowers in the sand and rocks of our former property. One of the first things I did in the spring after we moved here was to till a 1⁄4-acre garden. Seeing that large, clean area of dark, loamy soil made me anticipate a huge crop of berries and vegetables. The soil was so soft that I could just move it aside with my bare hands and cover the stressed roots of a bare-root strawberry plant. Within days, that same stressed plant would burst into life and erupt with green leaves, promising juicy strawberries in the years ahead.

As with most things in life, good things come with a price. The environment we created in our tilled garden favored a weed that was destined to become my nemesis: morning glories (also known as field bindweed, Convolvulus arvensis). By tilling the soil, I had unknowingly broken up a network of morning glory runners, and each of these runners, when masticated by the tiller, became a vibrant and greedy new morning glory, ready to quickly cover my strawberry plants with myriad vines. Like Hercules fighting the Hydra, every time I tried to pull a vine, it would break off deep in the soil and respond by sending up even more.

The county tree trimmers kindly left us a large quantity of wood chips, and I surrounded each strawberry plant with a deep layer of them. The strawberry plants looked so neat and proper surrounded by clean, uniform wood chips, but it was an illusion. Within days of being covered, the morning glories were poking their heads through the chips, and while it was satisfying to pull out long ropes of morning glory runners, I realized that I was fighting a losing battle. Those runners were intertwined with the strawberry roots, and there was no way to get them all.

Then, one day, I had an experience of garden serendipity while looking at a dried manure patty left by my milk cow, Kalindi. Cow patties crust over within days of being deposited, and nothing grows through them. If you lift one up, it’s dry and brittle, but always moist underneath. Additionally, any grass or weed growing on the verge of the patty is always more lush and green than the rest of the field, indicating that the plants near the patty benefit from its presence. I suspected that I could use cow patties as a mulch, and the mulch would probably be impenetrable to morning glories. The challenge would be to minimize cracks where the morning glories could escape their underground prison.

Billy has a background in construction, and I’ve helped him with several concrete projects. Concrete is very hard, but not really strong, being quite brittle. The strength in a slab, countertop, or foundation is actually the metal rebar or wire mesh that’s surrounded by the concrete. Keeping this in mind, I decided to make “patty mats” using a grass or straw mesh slathered with a slurry made out of cow manure. The mesh gives the mat enough strength to minimize cracking.

The method that seems to work best for me is to cover the area that I want to mat with a thatch of about 3 inches of loosely packed old hay. I then fill my manure cart with as many fresh cow pies as I can comfortably pull to where I want to spread it. Stirring with a hoe, I then add enough water to make a spreadable slurry. Once it’s workable, it’s just a matter of shoveling it over the thatch and working it in. I’ve tried using garden tools to work the slurry into the thatch but have found that using my feet is fastest and easiest. My Muck boots, which have rounded soles and very little tread, work perfectly for this job. Ideally, I try to get at least the top inch of thatch saturated with the slurry, and then leave it to cure. The glossy, wet mat will turn a darker color within an hour, and by the next day it will have assumed the color and dull texture of cardboard.

Using the patty mats, I’ve finally gained the upper hand on the morning glories. Weeding is minimal, and I simply mow the morning glories that escape from the edges of mats. There’s an additional benefit, too: I don’t have to water the garden even once, and some of my cauliflowers are tasty monsters.