Smother mulch for passive weed control
Greener, Easier Weed Control
The wet spring caused many plants to grow bigger and faster than ever, including some of our most troublesome weeds. I’m getting lots of questions about The Big Three: blackberries, buttercups, and bindweed. I have mixed feelings about some of these, especially blackberries. Although the most invasive blackberries (giant Himalayan blackberries and the lacy cutleaf European blackberries) aren’t native, they do feed a lot of wildlife. However, unchecked, they can eat a farm, as I know from experience. Years ago, when I first moved from a tiny city lot to an old farm on Bainbridge Island, I felt totally overwhelmed. Instead of a manageable little plot, I now had acres to contend with. Blackberries, buttercup and bindweed grew vigorously, choking out ancient garden plants like lilac and peonies. Until then, I had always gardened organically. Faced with a huge series of problems, too little time, and too much space, I was advised by many experienced garden designers to “get over” my ideals and “do it right”. The sensible way to deal with the mess was to use chemicals and “start all over”. Reluctantly, I went shopping. After reading the warning labels, I couldn’t bring myself to use anything but a spray bottle of Safer’s Blackberry and Brush Killer.
Terrified of harming my kids and my pets, I made them all stay indoors. Fearfully, I went to the furthest corner of the property and started spraying an enormous patch of Himalayan blackberries. As I worked, flocks of birds flew out of the bushes. In dismay, I stopped spraying. What was I doing? This felt like madness; dealing death instead of bringing the garden to life. I went back to the house, threw away the spray along with the old clothes I had been wearing, and took a long shower, trying to wash away any residue of poison. That day, I realized that I’d rather clear the land slowly, inch by inch, than experience a deadly silent spring in my own back yard for the sake of convenience. Thus, I cleared the land by hand, slowly but steadily. As the garden emerged, I found a treasure trove of antique plants, from silver laced primroses and trilliums to rare roses and flowering shrubs. The clearing took several years, but felt magical, like exploring the past. As I uncovered more plants, I developed a kinship with the long-ago gardener who had once filled that wild property with beauty.
Much Better Than Nothing
The funny part of the story is that when, weeks after that Black Spray day, I returned to the distant blackberry patch, I found that the spray had done exactly nothing. As I cut down the thick canes and chunked out the roots with a heavy mattock, I had to chuckle. For me, it didn’t matter that the poison attempt was a bust. It was worth a lot of hard work to know that the birds, the frogs, and the bees were as safe from chemical damage as my own small children and our beloved animals.
Since that day, I’ve stuck to green gardening, working as cleanly and healthfully as possible. Fortunately, all that hard work taught me many ways to rid gardens of dreadful weeds without harming the soil or the critters. I can thank those 7 acres for much of what I know about weeding, mulching, and bed building. Having so little time and money helped me become very efficient and caused me to question standard advice and try new things. Among the most useful technique (especially as I age) is the relatively passive one known as smother mulching.
Of Blueberries, Bindweed and Smothering
I’ve always enjoyed pulling ropy masses of bindweed, a task I find weirdly satisfying. Bindweed, aka morning glory (Convolvulus arvensis), is really quite a beautiful plant but it definitely has takeover tendencies. Fortunately, you really can get rid of bindweed for the most part (though birds will keep re-seeding it). The trick is mulching deeply and often. Mulching a running weed sounds counter-intuitive, but it actually makes great sense. It’s hard to get those rampaging roots out of heavy clay, but once the soil is opened up with humus, you can chase the roots far more effectively.
When I fill a wheelbarrow with bindweed roots, such a mighty endeavor gives me enormous satisfaction. Of course I never get every scrap, but I usually get most of it, thanks to my beloved horihori, a traditional Japanese farmers’ knife. After clearing an area of roots as best I can, I pile on a deep smother mulch of wood chips and wait. A deep (8-12 inch) layer of wood chips (not bark!) can even smother ivy in a few months. Check cleared areas every month or so and dig out new sprouts, which gets easier as the smother mulch opens the soil. In a few seasons, it is possible to clean up a really bad infestation and keep it clean using this technique.
Blueberries hidden by catmint instead of bindweed
The Ties That Bind
In defense of bindweed, a friend once told me a moral tale about bindweed that I never forgot. She was garden sitting for an elderly friend whose blueberry bushes were covered with bindweed. My friend spent days carefully picking off the tangled vines and digging out the roots. When the older gardener returned, she walked through the beds and stared at the berry bushes for a long time. Finally she said, “I imagine you think you have done me a favor.” Flabbergasted, my friend admitted that she did. The older woman sighed and explained that for years, she lost her berries to the birds. Only when they were hidden by the bindweed could she harvest her whole crop. Amazed? Me too.
Here in the PNW and elsewhere, native bindweeds have been more appreciated in the past. The soft, rather elastic stems can be used for tying up plants that need staking, from delphiniums and asters to peas and tomatoes. Bindweed has been woven into baskets and rough cloth and used to make a rather pretty dye for wool and linen. By chopping and boiling the stems and leaves, you can create soft yellows, gentle greens, and a sandy beige that’s nicer than it sounds. The color is quite persistent if set with a mordant such as copper (for deeper, duller shades) or alum (for brighter tints). Some folks brew compost teas from bindweed/morning glory and say it is very good for vegetables and fruit (particularly onions, so I am told).
A reader asked whether buttercups are toxic to chickens. Buttercups are indeed toxic for many critters, so don’t toss them in the coop. You can safely put buttercup foliage in the compost, but not the roots, as they’ll happily grow into new plants, lacing lustily through the lovely, warm compost pile. Lacking a green waste bin, you can dry weed roots on a tarp until they dry out, or toss them into a bucket of water until they rot (which happens fast in summer). Buttercups, like bindweed, can be eradicated over time by smother mulching, heaping a good 8-12 inches of coarse wood chips over an infested area. Buttercups prefer heavy, anaerobic clay soils, so as the soil opens and becomes better aerated, buttercups are less favored. Over time, a smother mulch will make the roots much easier to extract, while depressing the top growth as well. Onward, right?
Protect drains from deep mulches
I once cleared out some old shrubs only to find an old holly stump. (For 20 years I had been gardening in that area and never knew the holly was there.) Naturally, once the stump was exposed to light, it started to sprout. An old gardener friend told me to cover the stump, so I took an old bucket and overturned it, and left it on the holly for about a year. That old holly never did grow back!
Another good passive way to eradicate unwanted plants! Thanks Debra!