Methods for Killing Weeds in Your Yard

A Survey of Some of the Best Ways of Getting Rid of Weeds

Japanese knotweed in bloom.
Japanese knotweed (Polygonum cuspidatum) is one of the worst invasive weeds in North America. Toshihiko Watanabe/Sebun Photo/amana images/Getty Images

There are as many methods for killing the weeds in your yard as there are for delivering a death knell to anything else, I suppose (well, except for vampires). But not all methods are equally effective against all weeds. That's why it's important to "dig up some dirt" on a particular pesky plant before you get into a tussle with it. By studying your foe a bit before engaging it in battle, you gain an edge.

To that end, I survey eradication strategies for a few different common weeds below, strategies sent in by readers of this website. These folks have done battle with the particular weeds in question -- and lived to tell about it! Battle-tested, they're passing on the invaluable lessons they learned to you. Take advantage of this wealth of knowledge by reading the stories presented below.

In addition to those case studies, I've also linked to articles that relate my own experiences in dealing with particular weeds to help ensure that you'll be prepped as best as possible for your upcoming ordeal. If you're having trouble with identification, you'll want to consult my Weed Pictures gallery right away.

Killing Dandelions: What to Do, What Not to Do

The three weeds with which I begin are commonly encountered, yet they're very different from each other. Consequently, you may end up fighting each one differently. I think you'll profit from hearing the insights offered by the three weed warriors featured in these stories. I've also written about killing dandelions, myself, in case you'd like to do some follow-up reading.

One of the essential things to know about this common lawn weed is that it's a perennial; this means that you can't go about getting rid of it in the same way you would for an annual weed, such as crabgrass. You could, theoretically, eradicate crabgrass in spring by using a pre-emergent herbicide (assuming you get the timing correct, as I detail in How to Kill Crabgrass). That's because, being an annual, crabgrass must start its invasion anew each year (if you fail to eradicate it in spring, you'll have to wait and use post-emergent crabgrass killers on it in summer). But your strategy against dandelions will have to be different: since they're perennials, they maintain a permanent base camp on your lawn until you remove them entirely.

Reader, Gardner sets us straight on the best method for killing this weed, as follows:

Dandelions in the lawn are difficult to control because of their long tap root. The following three “solutions” do not work because of that tap root:

  1. Pulling the top part of the plant inevitably leaves the root behind, only to have the dandelion quickly grow back.
  2. Spraying the dandelion with Weed-B-Gon (or any weed killer that is designated for use on a lawn) will kill the leaves but leave the root behind, only to have the plant grow back.
  3. Using Weed-n-Feed, i.e., any product that's a combination of weed killer and lawn fertilizer, never gets enough of the weed killer to the tap root, so the dandelion survives.

You can kill the dandelions with Roundup (or any other non-selective herbicide), but this will leave dead spots all over your lawn where the grass around the dandelions is also killed. So what is the only reasonable solution? It’s a two step approach that involves first lifting the dandelion off its root with a “weed digger” (that inexpensive fork-like tool), and then spraying a small amount (less than a teaspoon) of Weed-B-Gon into the small hole that you just lifted the dandelion out of, to kill the tap root.

That’s right. The solution takes some work. But if you are determined, it won’t take that long to walk around your yard, bending over to lift out the dandelion, then kill the tap root with the sprayer in your other hand.

When you get done, take satisfaction that you figured out how to have the "best lawn in town" while still minimizing the chemicals used to just the small amount needed to kill the root (instead of wasting most of it). This makes it safer for the children and pets who play on your lawn.

Slaying Godzilla: Getting to Know Japanese Knotweed

This is another weed that I've battled personally, relating my own war-time experiences in an article on Japanese knotweed in which I dubbed it "Godzilla weed." Actually, to say merely that I've battled it personally amounts to a colossal understatement. The fact is, this is a weed with which I lived in close quarters for a significant portion of my life. Notoriously pesky, the plant is widespread across much of North America and the U.K. It has become so problematic in the U.K. that its very presence on your land reduces your property's value.

What's so odd about the Japanese knotweed story is that, despite it's being so common and so problematic, very few homeowners (even those plagued with it on their land) could identify it for you even if their lives depended on it. This weed lacks name recognition, plain and simple. And that's unfortunate, because if you don't know the name of a weed, you can't very well Google it to learn how to fight it properly, now can you?

Reader, Kate Copsey tells us about the method she's using to get rid of Japanese knotweed on her own property. Kate is the host of America's Home Grown Veggie Show on America's Web Radio:

David, I came across your article on the dreaded knotweed in the optimistic hope that there was a new way to eradicate this monster. I am sure you have had many contacts regarding this but I would like to add a personal war story.
A year ago we moved into a new home in New Jersey and what we feared was bamboo turned out to be Japanese knotweed. This was along with poison ivy vines, mile a minute vines, invasive rose and other nasties killing trees. I got help -- fast. The landscaper felled a swath of about 10 feet by about 50 feet around the property that was mainly knotweed. He sprayed weedkiller, came back 2 weeks later and sprayed again, then added about 6-10 inches of mulch.
Of course the Japanese knotweed growth was felled but the root ball was barely daunted and sent up new shoots. After a few disgusted words, I set to at digging out the roots. What I found was that the root ball, though heavy and large, was not difficult to take out (maybe the weed killer caused the roots to decay).

And yes, some bits remain. I stayed with that one area (persistent weeding of the tops, plus roots where I could get them) and this year indicates that not as much has come back. Some, I think, are new seedlings from last year's flowering period, others are maybe weakened from the root being taken away. I use a pick-axe and dig around it generously. So my method right now is to keep at weeding it out. A 10x15 ft piece of the bed that I cleared several times last summer took about an hour to weed tonight, and it likely will have to be done again (monthly maybe), but definitely not as long as it took the last year. My goal is to get the whole 50 ft weeded before the little devils get more than 6" high.
One thing that no one seems to mention is the orange roots: these things go yards and are over an inch thick in mature stands. Dealing with top growth and root balls is one thing, but these roots are a serious defense and I am not sure how to eradicate them. I have taken out what I can, but they inevitably break somewhere along the line.

Just as a note, I am working with the New Jersey Invasive Task Force with methods and although I prefer organic, this is serious enough that I will, indeed, use chemicals if needed.

Organic Bittersweet Control

OK, but what about those who are committed to staying away from chemicals in the pursuit of methods for killing weeds? Reader, Carole reported that bittersweet was swallowing up her property and sought my advice on organic bittersweet control. She wrote:

For a few years when we first moved in, I went around every few weeks and cut the bittersweet back, but hey! I'm 65 years old now, and anyway, I have better things to do with my time. The bittersweet has brought down a number of very tall locust trees, and I am just grateful that I am able to keep it out of several spruce trees that are important to me. I can't use herbicides because, well, I'm concerned about the other vegetation and wildlife. Do you have any tips you can give me for organic bittersweet control? Frankly, I wouldn't mind it staying around in moderation, but it appears that moderation is not something that bittersweet understands.

My response:

"Believe me, I sympathize with you. Like you, I prefer to stay organic; also like you, I have bittersweet on my property. Unfortunately, your options for organic bittersweet control are pretty limited -- mainly just a lot of pulling and cutting. But in the spirit of "moderation," there is one easy thing you can do to moderate bittersweet's growth:

"To slow down bittersweet's assault on your trees, simply cut the thickest vines. Just one cut (anywhere from ground level to waist-high, say) will be sufficient. The idea is to keep nutrients from passing from the root system up to the higher parts of the vine. This won't kill the bittersweet (since the roots will still be intact), but it will slow it down."

"I’ve just discovered an effective and easy way to deal with buckthorn and am wondering if it will work with bittersweet also. It’s only part of the solution, and works only on vines you can reach, but it helps.

"Basically, you just pull off all the leaves. The plant then starts to put them out again, sending its energy all the way out from the roots to the highest end. Then you pull off each leaf as it emerges, before it can nourish the roots. This way, not only are you easily and quickly (though fairly often) slowing the plant down, you’re also wearing the heck out of the energy in the roots.

"Cutting the branches, as another writer suggests, is an important way to allow your trees some breathing room. If possible, do it when there are no leaves on the vine, as a vine full of dead leaves can be fairly unsightly, if anyone cares. Also, do NOT use a chain saw; those pieces fly.

"Also, I have gotten rid of a lot of bittersweet just by pulling out the roots, although it doesn’t get all of them all at once. Wet soil gives them up most easily. After you’ve pulled as much out as you can, after a few days a significant part of the emerging root that’s left will die back, making it easier to pull more of it out."

For a more extensive treatment of this topic, see my full article on How to Kill Bittersweet. For more information about what's becoming an increasingly popular organic method for killing weeds, see my Vinegar As a Natural Weed Killer.

More Methods for Killing Weeds: Moss, Wild Violets, Poison Ivy

Attitudes toward lawns and wild plants are evolving in some quarters, with the former being deprecated in favor of the latter in the name of "biodiversity." For example, far from aiming for moss removal from lawns, some folks are cultivating moss plants as an alternative to lawns. What, "That's not my idea of a lawn," you object? If you're still in the camp that classifies moss as a weed, you'll be interested in this article:

Similarly, not everyone holds the same view of wild violets growing in the lawn. Are they pretty wildflowers to be admired or tenacious weeds to be killed? That's your call, and I acknowledge both viewpoints in my article on wild violets. If you're in the admirers' camp, you may enjoy learning some new facts about the plant in this piece; if you're in the killers' camp, you'll profit from the removal tips supplied by the article.

Poison ivy is another matter. Few will disagree that a property is better off without it. So the only question regards how one should go about killing it. Proper identification precedes eradication. To learn how to identify poison ivy, check out my pictures of poison ivy first. 

OK, now you know for sure what it looks like, so you're ready to start getting rid of it? Not so fast: this is one nemesis with which you can't engage in hand-to-hand combat! Here's an article that not only spells out a method for killing this weed but also furnishes some tips for removing poison ivy safely.

I'm an Organic Gardener, So What Advice Do You Have for Me?

Organic tips crop up here and there in the resources above, but for a more sustained treatment from the green living perspective please see Weed Control Without Chemicals.