Friday, April 28, 2017

Invasive Plants, Part 3: How I Eliminated Goutweed in my front Garden

Missed the first two posts? Read them here: Part 1 and Part 2

After years of battling Goutweed in our front garden, I decided to take drastic measures to get rid of it once and for all. The tactic I decided to use? I smothered it! That sounds rather vicious, but in reality, it was more work than anything else. 

Here's the method I used:

• Clear the area removing all the perennials and any small shrubs. Trees obviously have to remain as do large shrubs. 

Aggressive plants will sometimes shoot their roots right through those of other perennials. It's therefore necessary to lift each plant, wash the roots and inspect the root ball carefully. The root ball may need to be divided into smaller pieces to eliminate problems. 

Once the lifted perennials are completely cleared of invadersyou can replant them in another spot. Just be extremely careful with this step. The last thing you want to do is transfer an invasive plant to another area of the garden.

It's hard to show, but in the picture above you can somewhat see that orange daylilies have infiltrated a clump of hosta. The only way to separate the two plants is to dig up the clump of hosta. Then you need to clear enough dirt from the roots to see what's going on. Once you identify the two types of roots, you can carefully separate the two plants.

• Once the flowerbed is completely cleared and the perennials you want to keep have been set aside, go back and remove all the invasive plant roots you can find. Again, do this very carefully. Often any remaining root segments have the potential to produce new plants. It's best to dig back over an area two or three times to insure you have removed as many of the invasive roots as possible.

• To make it difficult for any missed root segments to regrow, you want to create a light barrier. 

I just happen to have President's Choice compost bags on hand, but any brown compost bag will do.

• To make a light barrier I decided to use brown paper compost bags and cut them up. Why compost bags? They are biodegradable and have less printer's ink than newsprint. A compost bag when cut open also creates a big, solid piece of paper. That large piece of paper covers so much more ground than a open spread of newsprint would.

You could use cardboard– it would work just fine, but you'll have to remove any tape or staples that hold the box together. These materials wouldn't break down and staples could pose a risk later on.

• With your scissors, cut along the outside corner of the brown paper bag all the way to the bottom. When you get to the bottom, turn the scissors and follow the bottom of the bag all the way around until you've cut off the whole bottom section of the bag.

With the bottom cut away, you should now be able to open the compost bag into one big rectangle of heavy brown paper. Don't throw away the bottom of the bag! As you will see in a minute, it has a use.

• Try to chose a windless day to avoid frustration with this next step. The goal is to cover the entire area with a solid barrier that will deprive light to any remaining roots.

• Lay the open piece of brown paper on the ground. Use a small stone or a small pile of mulch in each corner to hold the paper in place while you work. I used a single layer of paper, but a double layer of brown paper would be even better.

Overlap the pieces of brown paper by at least six inches. If you leave gaps, light can reach through the gaps.

Here is how I dealt with a small tree in the middle of my flowerbed. I cut the bottom section of the bag in half. Then I cut a U-shaped hole in the centre of each of the two pieces of brown paper. In the final step, I overlapped the two pieces together around the base of the tree.

Once I had the tree surrounded with paper, I went back to using larger sections of paper.

Once the paper is laid out on the ground, cover the whole area with natural cedar mulch. Don't be stingy! Make that layer of mulch at least 2-4 inches deep.

The mulch will do a number of things. Along with the paper, it helps to block light. The weight of the mulch will deter fresh sprouts. It will also help keep the paper a bit dryer. And finally, the mulch will make the area look presentable while the paper does its work.

Goutweed can really take over as it has done here in this garden.

Gardening in this area is now on hold for a month or even more. If sprouts do make it through the paper and mulch, dig them out. Create a new patch of brown paper to cover the hole. Add a fresh layer of mulch on top of the patch.

The limitations of this method:

Creating a light barrier may not work for every invasive plant or in every garden situation. 

Large shrubs can be surrounded with paper much like trees, but extra vigilance is needed as invasive plants can hide out at the base of a shrub.

If you deprive a plant of light in one area, it can travel to another. Should you decide to use my tactics, I would recommend you find a way to block the invasive plant in question from running into a new area of the garden. The easiest way to do this might be to dig a deep and wide trench around the problem space.

This method has worked pretty well for me and it is organic. I did have a few shoots make it up through the paper, but I removed them and patched the holes. After about a month and a half, I didn't have any new signs of the dreaded Goutweed.

My struggles are far from over. There is another patch of Goutweed in the backyard. Like housework, a gardener's work is never done!

Go back and read Invasive Plants Part 1 and Part 2.

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  1. So that's what I have!!!
    Invasive does not even begin to describe mine, and I did the deadly deed (transferred it by mistake to at least 2 other areas). :-(
    Thank you SO much for this. Now, not only do I know what it is, but I know what to do with it.
    Have a wonderful weekend, my friend!

    1. I hope you have a wonderful weekend too Lisa!

  2. I had that over my entire area surrounding my house. Like you, I won't use chemicals.
    I hesitate to say I believe I am completely done with the Goutweed now...but a grass a neighbor passed along is proving to be a tougher enemy.
    Very good info in this post, thank you

    1. Grass is super hard to deal with so you have my sympathies Sue! I have a small problem with grass between pavers and it is such a nuisance.

  3. Great post. Invasive plants can be different from one zone to another, I am in the process of eliminating fall blooming asters - here once established, and although lovely are real garden thugs.

    1. You make a good point about zones Adrienne. Some plants can behave in one area and take over in another where conditions are very favourable.

  4. great article! It boggles my mind that goutweed is still sold in garden centers - awful stuff

    1. I feel so sorry for the unwitting gardener who brings this plant home from the nursery having no idea how aggressive it can be.

  5. I'm going to do this with the remains of a gallica rose I've been trying to dig out since last spring. The roots and sucker roots go to China! I'm all tuckered out fighting with that fella. It's a beautiful rose, but trying to take over my garden. I can plant 3 or 4 roses in the place he was taking. For the sake of appearance, I will set some large potted roses and perennials on the mulch until I can plant the area again. A very timely post.

    1. Goutweed is pretty fine. Rose suckers would be more persistent and substantial, so if it were me, I'd use the heavier option in this case- cardboard. Hope it works for you Annie!

  6. I'm making headway against my goutweed opponent, but I've found the tagboard I was using wasn't enough to do the trick. I did have to use cardboard, and even the dreaded black cloth in one place. Connected to this area is a larger area where it's competing against vinca. And since the vinca is self controlling there (it's bordered, easy to edge, and stays to the shadows closer to the house) I'm leaving the vinca and simply pulling every darn goutweed leaf head that pops up. It seems to be working... it's been three summers; less came back last year, and hardly any came back this time.
    I will starve the villain out!

    1. I can so identify with your struggles Kathleen! I am glad you are winning the war!

  7. I used this method to rid my flowerbeds of grass that had taken over them. It took me three weeks of daily digging, detangling and sifting but for the most part I was successful. It took me several seasons to conquer the Centauria montana I mistakenly planted 10 or so years ago but I think I've succeeded with that too. I've tried to grow ajuga a couple of times in my Zone 3a garden but it doesn't come back. The lamium pops up all over the yard; my husband loves it so I've left it alone. Now if I could just manage the millions of Chinese elm and Manitoba maple seeds that blow into my yard every year...

    1. Eliminating problem plants is no easy problem, is it Jan. At least all your hard work with the grass paid off. Funny, Centauria montana is not a problem for me. I think it is because I have it located in an unfavourable spot (almost full shade). Some types of Lamium are quite nice. My favourite has silvery-green leaves. I hear you on the Manitoba Maple seeds. Myself, I have to contend with Norway Maple.


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