How to kill plants is something I get asked all the time in the context of “This plant is eating my garden”, or “How do I kill grass in my garden.”
So without further ado, here’s the current scoop on killing plants you don’t want in your garden.
Yes, I know it is a lot of work but this is the single best way to clean out a garden. The problem with this is that you have to be quite thorough to get the job done. With many plants, all that is required is a tiny segment of root left in the ground and it will regrow again.
So, double digging is a good thing and sorting through every shovel of soil is almost a necessity.
How to kill plants? Use patience and perseverance.
This is called garden renovation and if you’re looking at a badly infested garden, then this is what you’ll have to do to eliminate all the weeds (let’s call any plant you don’t want a weed).
There is no magic wand you can raise and simply eliminate a bunch of plants without disturbing others. It is slow and it is work but it is effective.
This dandelion (green leaf) was growing through the roots of this peony plant. I had to dig up the peony to get the dandelion – it was a very expensive Itoh peony so it was worth taking a bit of care with it.
How To Kill Grass
If you are talking about a large section of ground, then 10 to 15 layers of newspaper laid down on top of the grass or plants will smother them.
Wet the newspaper as you lay it down and lay it overlapping so there are no cracks for the plants or grass to escape through. After you have the newspaper laid down, you can put an attractive mulch over top of this.
Mulch them out! This above technique works very effectively to kill grass or large lawn patches so you can plant shrub borders.
This is particularly effective under trees where nothing will grow and you don’t want to water. The newspaper stops the weed and the bark mulch gives you a decorative look.
When you do this, you can grow shrubs and evergreens in this garden space and you might even grow a plant that doesn’t spread or expand (like a vegetable or annual flower) but you wont’ grow too many perennials in this newspaper mulch because they expand from year to year and will have difficulty pushing the newspaper aside as well.
Use An Organic Spray
You can use an organic spray such as industrial strength vinegar (acetic acid). This burns off the tops of plants such as dandelions.
But it kills anything it touches so do not spray it on good plants. If you spray it on lawn weeds, it will burn off the nearby grass as well.
Recipe I Use:
- one gallon of 7-10% acetic acid vinegar,
- 1 tablespoon of cheap cooking oil,
- 1 dash of soap as a spreader (important)
Note: former recipes I’ve given have included salt. This is no longer part of my recipe and in my tests, I can’t see a difference in effect on killing weeds.
- You do have to use pickling vinegar at 7% to get any decent kill – anything less than this is pretty much a waste of time in my experience.
In other words, contrary to what the Net tells you, regular household vinegar is a waste of time and doesn’t work.
You will have to vigilant using these organic sprays. The weeds, particularly perennial ones, will have lots of strength in their roots and will throw new top growth within a few short days or weeks.
As soon as they produce a new growth of leaves, you must immediately spray them again. The objective with perennial weeds such as dandelions is to force them to use all the food reserves in their roots so they don’t have the energy to produce a new leaf. Continual spraying of perennial weeds is necessary to really kill them.
There are a growing number of organic sprays on the market for specific problems (e.g. iron for dandelion control) I encourage you to check them out. I’ve use them and they do indeed kill dandelions (and another weed called “medic”) but no others at this point in the research.
Change the Growing Conditions
There is a body of research out there that points to some kinds of weeds or plants growing in different conditions and if you change those conditions, you’ll eliminate the weeds.
Moss in lawns is a perfect example. Moss thrives in conditions of low fertility. Once you start feeding your lawn and laying down extra grass seed, the moss tends to disappear under the pressure of too much food and competition. Raking it as well is a really good way to get this process started.
(But the complexity arrives at this point when you understand that low fertility is only one of several conditions that encourages moss growth.)
Thistles grow in this kind of soil condition, clover in this one. The reality is that it isn’t quite that simple in a mixed garden situation to eliminate one weed and leave another plant thrive. The best we can do for our gardens in a general way is to continue to add compost and try to create the best soils we can.
Vinegar will slow these down but kill the grass around them. You need to use multiple sprays
The reality of any kind of organic control is that it is not a one time event. It takes persistence and ongoing work to control both weeds and insect pests. There is no residual control of anything with organic controls so the residual resides with the gardener who engages with the garden.
So when you ask me, “How do I control this XX weed?” – the answer is pretty much going to be the same. Pick one of the above and go at it. Or pick several of the above and go at it. And be prepared to keep going at it.
Let me tell you my story – when we purchased our current property, it contained 7 of the most noxious weeds I have been writing about for over 25 years. It was as if fate conspired a great joke to give me every plant I’ve ever detested.
Five years later, 4 are gone totally, one is hanging in by germinating here and there, 1 has been reduced from a large 40X3 foot bed (Goutweed) to a few small stragglers and 1 keeps hiding under other plants but is now down to about 3 square feet. And I’ve accidentally released 2 new ones that I’m now killing as well (a stupid clematis and an ornamental grass)
I’ve done this with vinegar sprays, a shovel, cardboard along with mulch and persistence.
Let’s be honest here, there is a fantasy of being able to come onto a bit of ground and “just this once” spray something that will magically remove all weeds and problems. There is a sweet temptation to use it because – well, because it is a lot easier than digging. It is a lot easier than sweating out there.
I’m not even going to repeat all the data on the Net right now about how the increased rates of Parkinson’s disease in middle aged and seniors is directly related to using chemicals in the house and garden.
I’m not going to tell you about the rising rates of ADD, childhood cancers and deformities related to chemical use. Or how cancer in pets is rising.
I will simply say that it is wrong to use garden chemicals to save yourself a few steps and a little work when it contributes to the negative health of yourself, your neighbors, your pets and your children.
Wreck your environment, your air and your water to kill a small yellow flower on your lawn. Where’s the priorities in life?
End of soapbox – but that’s how to kill plants in your garden.