Secrets to a Weed Free Garden

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Robert Pavlis

Do you have a lot of weeds in your garden? Do you want to know how to get rid of them? Are you making a new garden bed and want to eliminate years of weeding? You have come to the right place.

In this blog I will provide you with solutions for both of these problems. Most people who have a lot of weeds in the garden have made two mistakes. They did not prepare the new garden properly and they are not mulching enough.

Weed fiasco in the garden - poor squash plant is trying to compete with a ton of competition.
Weed fiasco in the garden – poor squash plant is trying to compete with a ton of weeds.

Where do the Weeds Come From?

Before you can solve a weed problem you have to understand how and why you have weeds in the first place.

There are three sources for weeds.

Perennial Weeds Already in the Ground

Many new gardens are not started properly and perennial weeds are already there before you even start gardening. These weeds grow from existing roots that were there before the garden was made. They can be difficult to get rid of, especially if you don’t understand how they grow. I’ll explain that later.

Soil Science for Gardeners book by Robert Pavlis

Existing Seeds in the Soil

Plants have been creating seeds and dumping them on your soil for many years. Even if you buy bulk soil and bring it to your garden, it will contain thousands of seeds. They can be annual plants or perennial plants, but they are all waiting to see some light so that they can germinate and grow.

New Seeds

All of the other plants in your garden, including weeds, will produce seeds if you let them. Even the plants in your neighbors yard and the ones down the street are making seeds. These seeds get carried by the wind or by wildlife and some of them will end up in your garden. If they find the right conditions, they will start to grow.

Different Types of Weeds

For the purposes of this article, I am going to divide the very long list of different weeds into three groups; annuals, non-spreading perennials and spreading perennials.

It is not critical that you can identify every weed in the garden, but it is important that you can classify the weed into one of these categories. Doing so will help you select the correct action to eliminate them from your garden.

The best way to classify your weeds is to watch them and examine their root system. If you are a new gardener it may take some time to get to know your weeds.

Annual Weeds

Annual weeds sprout in the spring, grow quickly, and die during the winter. The bad news is that these weeds make lots of seed. The good news is that they die out on their own, and if you keep them from flowering, they can’t make new seed. This group of weeds is actually easy to manage.

Non-spreading Perennial Weeds

common plantain is an example of a non-spreading perennial weed
Common plantain is an example of a non-spreading perennial weed

A perennial is a plant that is not killed during the winter. It comes back year after year and lasts many years. I am using a wide definition of perennials which includes things like bulbs, grasses, and trees.

Some perennials don’t spread very much. Think of your favorite perennials in the garden, like a hosta. It does get slowly larger over the years, but it does not spread all over the garden.

A dandelion is a good example of a non-spreading perennial weed.  It has a tap root which does not grow sideways. Granted it will produce seeds, but we’ll deal with it’s seeds as if they are seeds from an annual.

This type of perennial will be there until you dig it out. Then it is gone for good. They are fairly easy to deal with.

Spreading Perennial Weeds

Canada thistle built by Dr. Merrill Ross to show the extensive root system.
Canada thistle box built by Dr. Merrill Ross to show the extensive root system, Purdue University.

This type of perennial spreads sideways forming new plants. In some cases they can spread very fast.

Some horticultural perennials behave this way. For example bee balm spreads quickly if it has good growing conditions. Goutweed also spreads.

This type of weed can also spread by seed, but our main concern is the fact that it spreads by underground runners, also called fhizomes. It can be very difficult to get the rhizomes, out of your soil. This is the weed that is most difficult to control.

Dr. Merrill Ross, Professor of Weed Science at Purdue, is well-known for his Canada thistle boxes. The box shown is 4 ft tall by 2 ft wide by 8 ft long. It was filled with soil, planted with one 12-inch long Canada thistle root, and then received natural rainfall for a period of 4 months. The soil was then washed out to reveal the roots.

You can see that the plant has made several new above-ground growths and an extensive root system, that is impossible to pull out. You can keep pulling out new growths, but new plants will just grow from the roots you leave behind. This is one nasty weed that just does not deserve to be called Canadian 🙂

Starting a New Garden Bed

Serious weed problems almost always start with mistakes that are made while making a new bed. If you don’t make the bed correctly, you are guaranteed to have a huge weed problem.

You can’t eliminate the existing seeds in the soil, but you can do something about the spreading perennial weeds. You have to get rid of them all, including the rhizomes and roots hidden in the soil.

Digging up the soil will not get rid of these weeds. You can get a lot of the roots, but each piece of rhizome that breaks off is ready to grow a new plant.

Roundup works very well. It is a chemical that is absorbed by the leaves and transported to the roots, where it kills the rhizome. It takes about 10 days to work and after that you can plant. Contrary to what is written on social media, it is an extremely safe chemical.

If you prefer a non-chemical approach, I suggest using what is affectionately called the lasagna method. Cut everything as short as possible. Then cover with 4 layers of overlapping newspaper. Make it wet so it does not fly away in the wind and then cover with either top soil, or a mulch such as wood chips.

Do NOT plant through the newspaper as so many recommend. It just provides a way for perennials weeds to start growing right into your new plants. Wait two months in warm weather (longer in spring and fall) until everything under the newspaper is dead. Don’t rush this process or you will have perennial weeds.

You now have a bed that is free of perennial weeds, including lawn grass.

Should You Rototill or Dig Up a New Bed?

I used to do do this because a lot of old time gardeners advise this, but it is not necessary in most cases and it DOES create more weeds.

Digging of any kind brings weed seeds to the surface where they get enough light to germinate. Digging also cuts the rhizomes of spreading perennial weeds, producing many new baby weeds.

In addition to making weeds, tilling or digging destroys soil structure and harms soil life. Don’t do it.

Some people like to rototill or dig up a new bed to add organic matter such as compost. That makes some sense, but you can add compost later and let nature dig it in for you. You will have less weeds by NOT digging.

If you decide you must dig or rototill, use the lasagna method after digging to kill perennial weeds before you plant.

Keeping Grass Out

Lawn grass is a spreading perennial weed and it is a big problem if it gets into your beds. The above advice will kill any that is present, but the bed is usually right next to the lawn, and lawn grass will try to grow back into the bed.

You need some type of edging to keep the lawn grass out. I won’t go into details here but there are many options. None of them are perfect. No matter what you use, keep an eye on the edge, and pull out any grass sneaking into the bed. This is critical. Once it starts to grow into the bed and into your plants, you have lost the battle.

Keeping Weeds Out With Mulch

If you followed the above advice, you now have a new bed that contains no perennial weeds, but it does contain weed seed. The best way to stop the seed from germinating, is to keep the soil dark. The easiest way to do this is with mulch.

Mulch for a Vegetable Bed

The best mulch for a vegetable bed is straw (some people prefer hay). It can be laid down nice and thick once your vegetable seeds germinate. Or lay it around transplants.

It keeps seeds from germinating, holds moisture in the soil and slowly decomposes to add nutrients.You can also use wood chips as described below but you need to be careful that the wood chips don’t get mixed into the soil, or you might have a nitrogen deficiency.

Mulch for an Ornamental Bed

The best mulch for an ornamental bed is wood chips. These are the chips produced by arborists when they take down a tree. Add 3-4″ across the whole bed and you will get almost no weeds germinating.

Wood chips slowly decompose as bacteria and fungi go to work. The microbes need nitrogen to do their work and they take it from the soil. This might sound like a problem, and many people think it is, but the microbes only take nitrogen from the top 1/4″ of soil. They do not affect the nitrogen level deeper down where the roots grow and therefore this does not take nitrogen away from the plants.

Mulch stops weeds from growing. Left image has no mulch and the right image has wood chip mulch and planted daylily seedlings, with only one or two weeds, by Robert Pavlis
Mulch stops weeds from growing. Left image has no mulch and is full of weeds. The right image was planted with daylily seedlings and mulched with wood chips, it has only one or two weeds, by Robert Pavlis

The picture above shows two areas of the garden that are about 4 feet apart. Both were dug up to form a new bed. The one of the right was used to plant some daylily seedlings and then it was mulched with wood chips. You can see a couple of weeds, but almost all of the green leaves you see are daylilies. The one on the left was left bare. It is all weeds. The pictures were taken about 6 weeks after digging up the garden in early August.

Mulch and New Weed Seeds

What about new weed seed that floats in from other gardens? You can’t stop some seed from settling on your new bed, but when the seed lands on the mulch, one of two things happens.

The seed might germinate, but since it is too far above the moist soil, it does not live very long.

Small seed will fall through the cracks in the mulch, and once it is too deep, it does not get enough light to germinate.

It is not a perfect system. A few weeds will germinate and grow, but weeding these will be a small task compared to soil without mulch. Most of the seed that does germinate will be at points where you let the thickness of mulch get below 3″.

Mulch is Not Perfect

You killed the perennial weeds so they won’t grow in your new bed. Or will they?

There is one problem. Some spreading perennial weeds can grow a long distance underground before coming to the surface. Bindweed is a good example of this. It could be growing 30 feet away, and grow under ground to come up in your new bed.

It is not a perfect system, but most perennial weeds will not show up in your new bed.

Keeping Weeds Out With Plants

Plant hosta close together and you never have to weed under the plants, by Robert Pavlis
Plant hosta close together and you never have to weed under the plants, by Robert Pavlis

There is even more you can do to keep weeds out. Grow plants that are self weeding. This applies to ornamental beds more than vegetable beds.

Self-weeding plants are ones that grow thick enough to keep sun away from any weed that tries to grow under it. Here are a couple of examples.

Hostas are Self-weeding

Hostas, especially the bigger ones, produce large leaves that keep all sunlight from hitting the ground. Plant them close enough so there is little space between leaves of adjourning plants, and you never have to weed the bed.

Clumping Perennials are Self-weeding

Geranium sanguinium is one of my favorite all time perennials. It flowers all summer long, and makes a nice neat clump that never needs to be weeded, by Robert Pavlis
Geranium sanguinium is one of my all-time favorite perennials. It flowers all summer long, and makes a nice neat clump that never needs to be weeded, by Robert Pavlis

Other plants make nice thick clumps that just don’t let anything else grow. My all-time favorite perennial in this group includes Geranium sanguinium. This plant grows so thick you never have to weed under it, and it flowers all summer long. You don’t even have to clean it up in spring – it does that for you too.

Staying Weed Free

Starting with a weed free bed is 95% of the battle.

Some new weeds will show up and the key is to go after them right away; don’t let them get established. Don’t let perennial weeds get big enough to make runners, and don’t let any weed flower and make seed.

Don’t Use Weed Barrier Landscape Fabric

Manufacturers of this product, some landscapers and new gardeners like to use weed barrier, also called landscape fabric. The name says it all – it must stop weeds – right? Wrong. Landscape fabric does not work. It will look good for a couple of years and then you will hate it.

It is not needed if you use mulch as suggested.

What Can You Do With a Weedy Bed?

Lets say you did not find this blog until after you made a bed and it is now filled with weeds. Or, maybe you bought a new house with an existing weedy bed. What can you do now?

Step one is to understand the weeds. Are they annuals? Non-spreading perennials? Or Spreading perennials? You probably have some of each in which case try to figure out how much of each you have and deal with the most pressing problem.

Dealing With Mostly Annual Weeds

If you have mostly annuals, the situation is not so bad. By next spring all of these will be dead, and all you have to do is prevent new seeds from germinating. Keep all weeds from flowering to reduce future weed problems. It is best to rip them out, but at the very least pull off all flowers before they open. Then mulch as described above.

By spring most of your weed problem will be solved.

Dealing With Non-spreading Perennial Weeds

Mulching non-spreading perennials may kill the shorter ones, but many will just grow through the mulch. You have to get rid of these plants. No matter what else you do, prevent them from flowering.

You can dig them up, making sure you get most of the root system. This works well, provided you can get to them without harming your good plants. It is like digging out a dandelion in a lawn. Try to get as much root as possible, while doing the least amount of damage to the lawn grass. I describe this in more detail at the end of the post.

You can also use a small brush and paint a small amount of Roundup on the leaves of the weed. As long as you don’t get any herbicide on the good plant, it will kill the weed without any ill effect on other plants. It also takes a very small amount of Roundup.

Dealing With Spreading Perennial Weeds

If you have these, you have a bigger problem. You can’t cover them up – they will just grow through the mulch. You can’t dig them out because any piece of runner left behind will still grow.

In a vegetable bed, it is probably best to try and dig out as much as you can. Then at the end of the season, use the lasagna method to kill the perennial weeds. You may need to forgo your garden for a year in order to do this. Or you can grow vegetables in half the space, and clean up the other half with the lasagna method. Then do the second half the following year.

Ornamental beds are more difficult since the planting is permanent.

For less aggressive weeds, such as lawn grass you might be able to pull it out. Pull as much as you can, and then return in a week or two and repeat the process. With care you can get this out of ornamental beds. But this won’t work with quack grass, bindweed or goutweed, all of which make too many deep, long runners.

If the number of such weeds is small compared to the number of ornamental plants, try painting with Roundup as suggested above. It works very well.

If the weeds outnumber the ornamental plants, it might be best to dig them all up and start again. Remove all good plants, and inspect them very closely to get all weed rhizomes out of the root system. Plant the good plants in a temporary spot. Use the lasagna method to kill off all perennial weeds in the original bed. You can then move your ornamental plants back. This is a lot of work, but other than using a herbicide, it is the only way to get rid of spreading perennial weeds.

Don’t Use Lasagna Method on an Existing Planted Bed

Lots of online sources recommend using the lasagna method for an existing bed that is fully planted. You lay newspaper or cardboard around your plants and then cover with mulch. Most of these people repeat the process every few years – I wonder why?

Think about it for a moment. Weeds under the paper will be killed. But weeds around your existing plants won’t be covered with paper or mulch so they won’t be killed. You’re forcing weeds to grow right into the crown of your good plants – the exact opposite of what you should be doing.

Using the lasagna method on an existing bed does not make sense because it can’t remove existing weeds from under your plants. It only works if you remove all of the good plants first.

11 Ways to Make Weeding Easier

Here are some tips to make weeding easier and more effective.

  • Weed the day after a rain or after watering – weeds pull out easier in moist soil.
  • Stop a weed from flowering and you stop hundreds of future weeds.
  • Get the root out – if the root stays behind you did not get the weed out.
  • Pull slowly to give the plant a chance to release itself from the soil.
  • Pull the weed out with your hands or a trowel – it is harder work than using a hoe, but much more effective.
  • Don’t disturb soil unless you have to.
  • Make sure you remove several inches of root on weeds with tap roots, like a dandelion. Then there is a good chance it will die.
  • Don’t use home remedies as a herbicide – they are all nonsense and don’t work.
  • Pull weeds when they are small.
  • Pull weeds every week – don’t let them get ahead of you.
  • Start weeding in early spring.
  • Weeding creates bare soil – move the mulch back after pulling a weed to prevent new weeds.
  • Weed early morning when it is cool – you will weed for a longer period of time before you get tired.

There is a proper way to pull weeds.

  1. Grab the weed as low to the ground as possible.
  2. Make sure you have as many of the leaf stems in your hand as possible before pulling.
  3. If it is a big plant and a non-spreader, use the other hand to stick a trowel into the soil close to the crown of the weed.
  4. Pull very gently and ease the roots out of the soil.
  5. If you are also using a trowel, pry the trowel back at the same time as you pull so that it helps lift the root system.

If most of the root system comes out – you have success. If you only get a handful of leaves – you failed and you need to come back in a couple of weeks and do it again.

For spreading perennial weeds it is a good idea to gently dig up the soil around the weed, trying not to break any of the rhizomes. Slowly pull the weed out, and follow the rhizomes along in the soil, loosening it as you go. Trying to get every last piece. It is hard to get it all, but the more you get, the more you harm the weed.

References:

1) Image Source for common Plantain; F. D. Richards

2) Image Source for Canada Thistle Box; https://ag.purdue.edu/btny/ppdl/Pages/POTW_old/Weekly_Picture5-2-01-3.html

 

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

25 thoughts on “Secrets to a Weed Free Garden”

  1. Hi Robert, great read. Been dealing with a terrible bindweed and quackgrass problem. I’m confused if the lasagna method will work for these rhizomal weeds or not. I am working towards organic so will not spray. Thanks!

    Reply
    • Yes and no. While the paper is there it prevents them from growing. Once the paper decomposes they can grow again.

      Quack grass is less of an issue because the runners don’t go very far, so it will probably be killed.

      Bindweed travels many feet underground – lasagna won’t kill it. It is time for Roundup,

      Reply

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