Every year between April and June, I go on a weed-killing mission to eradicate garlic mustard. I pull every one of these noxious, highly invasive weeds I can get my hands on, and yank them out. Getting garlic mustard — or any weed for that matter — under control is an incremental process requiring elbow grease, a tool or two, and persistence.
However, because more and more homeowners and gardeners are trying to steer clear of glyphosate (the active ingredient in Roundup and other herbicide products), they're turning to natural alternatives. And while there are tons of DIY formulas online, it's not necessarily a great idea to mix up your own. Read on for for a little debunking, as well as other ways you can kill weeds naturally and safely. Oh, and how you can prevent weeds from growing in your yard in the first place, of course.
Homemade weed killers can be suspect
Making your own weed killer with easily available and affordable ingredients — such as vinegar, salt, dish soap, baking soda, and other household chemicals — does not make it a "natural" weed killer. Just because you frequently use these products in your home without ill effects does not mean that you should be using them in your garden. As Michelle Wiesbrook, Extension Specialist in Weed Science at the University of Illinois, points out, unlike registered products, homemade weed killers have not been extensively tested. Their long-term environmental effects are unknown, and they can potentially do more harm than good. Commercial weedkillers are usually formulated to break down or dissipate in a controlled way and within a certain amount of time. On the other hand, a weed killer made with the household cleaner sodium borate (Borax), is highly mobile in the soil and can unintentionally damage plants nearby that you want to keep.
There are other hazards to consider, too, according to Wiesbrock. Vinegar, one of the most commonly recommended weed killers, only works when it's highly concentrated. Horticultural vinegar contains 20 to 25% acetic acid, whereas household vinegar is only a 5% acetic acid solution. When you mix up the highly concentrated vinegar with water, you must be extremely cautious as splashes can lead to skin burns and permanent eye damage. And using boiling water on your weeds (another frequently recommended way to kill weeds) is also not without risks. Depending on the number of weeds you need to kill, it means lugging multiple vessels filled with boiling water across your yard — you can imagine how that might be dangerous.
Instead of a homemade weed killer, try using an organic herbicide that is listed by the Organic Materials Review Institute (OMRI) for organic use. Look for the "OG OMRI" label on the product packaging. If you have qualms about it being pricier than your own homemade concoction, take into consideration the possible costly damage to other plants, environmental contamination, and health hazards for your family and pets.
ID your enemy
Often, home gardeners reflexively reach for a weed killer when one isn't necessary. I cringe when I see people walk around their yard spraying every single dandelion, a job that can be done just as well and in the same amount of time by removing the dandelion and its roots with a soil knife or a dandelion puller.
Before you apply a weed killer, determine whether you are dealing with a few weeds that can be pulled by hand, or an infestation that warrants the use of a weed killer. Also decide if it's really a weed that needs to go. Having a goldenrod or a milkweed pop up, for example, can actually be beneficial, because these plants attract butterflies and pollinators. Native insects have far too few food sources available in our home gardens and by leaving some of those plant volunteers alone, you are helping along biodiversity and the entire food chain.
Surprisingly, this even applies to plantains, a non-native weed commonly found in turfgrass. As Doug Tallamy, founder of the Homegrown National Park, writes in his book, Nature's Best Hope, plantains provide food for the hitched arches moth, buckeye butterflies, and the giant leopard moth. The latter is such a striking beauty that after I spotted one in our yard last year, I look at the plantains in our lawn in a totally different way.
Singe your weeds
When you pull weeds from the soil manually, it brings weed seeds to the surface where they will start to germinate. A flame weeder does not disturb the soil and it is environmentally safe because it does not involve any toxic chemicals. Using a flame weeder can be an effective, chemically-neutral way to kill weeds, especially those growing in gravel walkways, between paving stones of a patio, or in sidewalk cracks where they are difficult to remove manually... but they're not without their cons.
The downside is that flame weeders don't work well on weeds taller than two inches, and they don't kill the roots. Perennial weeds will grow back; therefore, flame weeders are best used on annual weeds. Keep in mind that a flame weeder creates extreme heat (up to 2,000 degrees Fahrenheit) and it must be used with utmost caution, never in dry conditions nor anywhere near fences or structures that could catch fire.
Suppress your weeds
Ideally, you'll prevent weeds from growing in the first place. There are two ways to do this: by planting densely or by applying a thick layer of mulch. Weeds will grow in any spot of bare soil, so don't give them a chance. In a newly planted yard or perennial bed, you can also use annuals such as wildflowers to fill the empty space, and mulching not only suppresses weeds but also keeps moisture in the soil, which cuts down on your need to water your plants.
Choke your weeds
If you aren't in a hurry, depriving weeds of sunlight, air, and water can be an efficient way to treat a larger weed-infested area. Seamlessly cover the area with durable agricultural black plastic sheeting and secure it with landscape pins or lots of rocks so it won't blow away. You can weigh it down further with a thick layer of mulch, leaves, twigs or small branches. It can take a season or more for the weeds to die before you can remove the plastic and replant the area.
I have successfully used this method also on other unwanted plants, including Houttuynia cordata, aka chameleon plant, a horribly aggressive ground cover. I was unable to remove it using any other method because as long as there are bits of roots left in the ground, it regrows.
Be a smart hand weeder
No matter what you do, there will always be weeds that require manual removal. Because hand-weeding is cumbersome and physically demanding, be a smart weeder: Use sturdy, ergonomic tools, learn how to let the tool do the work (not your wrists and back), weed after a rain when the soil is soft, and remove the weeds while they are small and before they go into seed and spread further. Just always make sure to remove the entire root system in order to get rid of the weed once and for all.
Some weeds, like the notorious garlic mustard, should not be composted under any circumstance, because their seeds remain viable even in a hot compost pile. To dispose of them safely, place them in plastic bags and throw them in the garbage.
In sum, there are many ways to combat weeds without using your household chemicals. So you can leave them for what they're intended for: cleaning your home.
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