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 ensure 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 an 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 removed, 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 by paper, I went back to using larger sections of the 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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40 comments:

  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!
    xo.

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

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  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

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    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.

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    2. I have a very difficult grass problem. No matter how much I spray or attempt to get rid of it, it keeps coming back. Does anyone know how to permanently rid their garden and yard (in my case, large) of the grass?
      Thanks.

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    3. Hi Sue, What method did you use to get rid of your Goutweed problem?

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  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.

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    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.

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

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    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.

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  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.

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    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!

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  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!

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

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  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...

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    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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  8. We accidentally brought over some yarrow from my Mom's after her passing! OMG It is now out into the yard! Got rid of it in the garden area but it is thick in the grass now! YIKES!

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    1. I have yarrow in my garden, but thankfully it isn't a problem. You must have ideal conditions for yarrow in your garden and yard. It can get out of control. What a shame that a keepsake plant has turned into a problem.

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  9. I have Norway Maples in my yard. Maple trees are growing everywhere!! I am constantly pulling them up. So far, that is working. But strawberry has taken over my back yard. there is no longer any grass there, just strawberries!! I have been told to toss grass seed when I know it is going to rain. Will this work? Dean Mc

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    1. Grass is pretty dominant and can often out compete other plants. I fear however that you may end up with a mix of grass and strawberries, if you simply throw down grass seed. Sadly there are no shortcuts in gardening! You'd be better to get rid of the strawberries first. You could pull them or my method of smothering them might work.

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  10. I have been able to keep my goutweed under control as well as loostrife. And
    Latium that is growing nicely under an evergreen tree. As long as these plants don't go afoul and I can stay in top of them I am ok. The one horrendous groundcover that I am so very sorry I brought it onto my property is chameleon - houttynia. Lordy this groundcover is absolutely awful. It spreads like a cancer it's main root pack sending tendrils underground that look like spaghetti noodles. Very hard to eradicate. Leave any piece behind and it roots itself. I have a wheelbarrow full right now of a planting bed dug up twice - one with shovel and hoe and now with hand shovel and I'm still picking pieces out! I am so sore and can't wait to be done with this however I am seeing one or two pieces popping up in my other beds further away so must get on it before it takes on another life innanother bed. Stay away from this horrible pest! And...I'm with you on the Norway maple and it's little seed spreading devices. A stately beautiful tree that tries to populate itself by sending out seeds that fly all over and root anywhere. Ugh. That's why a gardeners job is never done! Good luck everyone. I'm 63 and have been gardening all my life and love it yet we still make some mistakes! ��

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    1. Thanks for sharing this cautionary tale! Hopefully you've saved others from making the mistake of buying chameleon for their gardens. It sounds like a nightmare plant!

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  11. Do you have any suggestions to help kill Cannas? I thought I had dug up all the bulbs but they still kept coming up. I then did two layers of cardboard with a thick layer of mulch and they grew up through that!

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    1. I haven't had this issue, so l looked up and found a solution that I think will work:Use a sharp-pointed trowel to dig under the rhizomes, taking care to get the entire roots out of the ground. Offshoots left behind may sprout new growth. If digging is not an option, cut off new canna growth and foliage as it appears. Doing so repeatedly probably will kill the plants.
      I'd dig out what you can. Use the cardboard again. Make sure to overlap the pieces by at least 6". Cut down any shoots you seeright away and be vigilant about it. The roots will get weaker for lack of food from above the ground. We tried this technique with knotweed. It takes time, but eventually it works. Sorry there is no faster cure.

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  12. Hi I've found your blog via Hometalk, and I have tried a similar approach for that dreaded garlic mustard by spreading a thick layer of maple leaf mulch which I make myself in the fall (we have a ton of maples) and it does help somewhat, although I have to go through and pull them again the next year. I've been working on one manageable section at a time, but we have 2 acres in the woods and it is a daunting task. I did not think to use bags as a barrier... I'll give that a shot and see what happens. Thanks so much for your interesting and informative posts!

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    1. Hi Patti, Garlic mustard has become an environmental problem. It's a prolific self-seeder. I was pulling some out of my garden just yesterday! At least it is easy to pull out. To break the cycle I think you need to concentrate on removing the plant ( or at least the seed heads) before they drop their seed. Seeing as you have a lot of ground to cover, I'd concentrate on the seeds and decapate as many plants as possible. All the best!

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  13. The previous owners of my home planted vinca under the deck. Why?! I am fighting a losing battle with this stuff. It is growing up the side of the house. I tried cardboard but it just won't stay down. Any ideas? I thought about covering the entire area with a tarp. Would this kill it?

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    1. I haven't had to deal with periwinkle but I hear that is a nightmare. I found some advice for you that I think will help:
      Remove the periwinkle runners from the ground with a garden rake. Stuff the removed runners into a garbage bag. Use your hand instead of the garden rake when removing runners near other vegetation that you do not want to harm.
      Dig the periwinkle and its roots out of the soil about 4 to 6 inches deep. Dump the soil, plants and roots in a garbage bag. Do not discard the soil or plant in another location. Doing so will result in new periwinkle growth in that area.
      Cover the area with black plastic. Place large rocks, blocks or wood on the edges of the plastic to weigh it down. The plastic will heat the area underneath, killing the plants. Leave the plastic in place for 4 to 6 weeks. Examine the plastic regularly and replace it if the black plastic develops holes or rips.
      Monitor the area regularly and remove any new periwinkle growth and its roots with a shovel. Place the plant and soil in a garbage bag.
      Here's a link to the source information: http://homeguides.sfgate.com/kill-periwinkle-killing-everything-else-21943.html

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  14. I read your article on how to smother invasive weeds with enthusiasm. I have a real problem with gout weed growing underneath my cedar trees. My back yard is lined with cedar trees and I am concerned the paper bag/mulch method will deprive them of water. I don’t want to kill my cedar trees. Will the smother method harm them? Thank you in advance.

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    1. I have not used this method in a similar situation to the one you describe, so I can't speak from experience. All I can do is share what I do know.
      Black plastic is often recommended to smother/solarize weeds. I wouldn't use this method for the area under your cedars! It won't allow water to reach the roots. Cardboard is another material that is often used to suppress weeds. It is porous, but may slow down the flow of water. Unlike plastic or cardboard, paper is quite porous so water will wet the paper and soak through (so much so that the paper degrades over time and you may have to recover the area with a fresh layer of paper and mulch mid-summer). Cedar mulch is also porous, so it will also allow water to soak through to the cedars.
      If you are still concerned, try out a small area and see how things go. Getting rid of goutweed is not easy, so keep at it. You may find goutweed is hardiest to get rid of right at the base of the cedars themselves. Try to create a paper collar at the base of each cedar (tons of work I know!).
      Sometimes we gardeners must pick our battles. If the area under the cedars is isolated and not joined to the rest of your garden beds, you may even consider leaving it as a groundcover. If the goutweed looks messy mid-summer, shear it right back to the ground and it will flush back with fresh green growth. Remove any seed heads so it does not spread anywhere else.
      P.S. My husband and I recently discovered that they sell roles of brown paper at Home Depot in the paint section. As you have a large area to cover, a whole roll of brown paper might be handy. Good luck!!

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    2. Thank you so much Jennifer.

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  15. I just stumbled across this post today after 2 hours of digging. I bought my house 7 years ago in the fall, and the gout weed was already in full swing. It's invaded my peonies, hostas, and rose of sharon. I would hate to lose these beautiful mature plants, and am afraid if I try to move them I will kill them (the peonies in particular, since they are rooted at the base of a maple tree).
    I've managed to dig up a fairly good area around my other perennials, just not the rose of sharon (of which I have a full row along the back fence). If I use this technique, will these bushes be able to recover? I'm willing to dig yearly around the perennial garden but along the back fence has become just too unmanageable.

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    1. Hi Lynne, I will be honest–you have your work cut out for you. On the up side, I have used this method in two areas with great success against goutweed (less success with ditch daylilies which I have had to dig out).
      How this method works is depriving the goutweed foliage of sunlight. The paper and mulch combination are porous so it still allows water to reach the roots of other plants or shrubs that have not been covered.
      For under the Rose of Sharon shrubs–By now your goutweed might be up and growing. Take a whipper snipper and mow it to the ground (taking care not to hit the shrubs). Mowing the goutweed will help the paper sit better as the surface of the soil will be flatter. Cutting it down will also stress the goutweed more by depriving it of foliage. Do your best to remove the goutweed at the base of the shrubs (hard work I know!). Bring the brown paper right up to the base of each shrub (make a collar as I showed in the post). Also be very careful to overlap pieces of paper (goutweed will take advantage of any breaks that allow sunlight). You could even lay down a double layer of paper as an extra measure in this area. Once you have the area covered with paper, add a good layer of mulch. If any goutweed does make it back up, brush aside the mulch, apply a patch of new brown paper and recover the area with mulch.
      In the area I did in the backyard, I had a Beauty Bush. It made it through this process just fine. Water still reached the roots. I did have to go back in however and remove goutweed that stubbornly reappeared at the base of the shrub.
      An area that has mixed perennials can be more tricky. I had a peony in the area I did out back. Do your best to remove the goutweed around the peony. The goutweed roots are fairly shallow and the peony's roots are deeper. At the very least, remove any goutweed foliage (thereby starving the roots). Lay the paper in a circle around the crown of the peony and mulch. You may have to go back in several times to remove any goutweed that comes back. If you end up needing to get drastic, I have moved a peony. They are hard to dig up, but you can do it. Try the paper first and see how it goes.
      Hostas may be even tricker. Goutweed can shoot right through the root ball and become entangled in the hosta roots. I'd recommend digging up the hosta and rinsing off the roots so you can hunt for any goutweed roots. Divide the hosta just to be sure you get it all. Goutweed roots are whiter. Where I live it is still okay to dig up hostas. If you are south of me, you may have to wait for the fall. In the meantime, do your best to bring the paper right up and under your hosta. It will help lessen the vigour of the goutweed.
      This is a big job. Don't allow yourself to get discouraged and put the house up for sale. Tackle one area at a time and see some success. It will give you the confidence you need to tackle the rest. You can do this!

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  16. Hi Jennifer,
    Do you think its best to try and dig up as much of the Goutweed plant and roots as you can and then cover with the brown paper and mulch or is it better to remove the leaves and stems only( and not disturb anything underground) and cover with paper and mulch ?

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  17. If you remove as much of the Goutweed as possible both above (leaves and stems) and below the ground (roots) you will increase the odds you will get rid of it completely in one go. Level the ground after you dig and then apply a good layer of paper and mulch (this method works by blocking the light from reaching the Goutweed).

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  18. In a comment above you said "If the area under the cedars is isolated and not joined to the rest of your garden beds, you may even consider leaving it as a groundcover." I'd be happy to leave a section of goutweed as ground cover. Can it be contained with a below ground barrier? I've seen a 10" grass barrier. And there are products that are even wider. I would be satisfied just keeping it in its place. Thoughts?

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    1. I can only speak to my own experiences. I have had Goutweed sneak across a flagstone path so it does travel!
      There is one garden I visited on the Bruce Peninsula that has a mass of Goutweed under a tree. Though I dislike the plant, I have to admit it looked pretty massed. This particular gardener poured a 8" band of concrete to edge the bed.
      A below ground barrier might work to curtail your Goutweed, but I can't speak to experience. What might be easier/cheaper is to edge the area really well. I use an edger to cut my line. Then I do in with a shovel and make the trench deep (6-8"). Using the shovel I angle the outer edge of flowerbed down toward the edge cut into the grass. Then I cover the exposed area of soil in the flowerbed with a generous layer of natural cedar mulch. Compact the mulch with your foot. Compaction will deter weeds and may even keep the Goutweed from traveling toward the grass.
      Sorry if this sounds a bit complicated. It's hard to explain, but easy enough to do. Good luck!

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  19. This battle with your goutweed got me thinking. I have a real issue with sumac. At our old house we had sumac and only ever had a runner or two. One would die off as another matured. Very workable. Foolishly I thought this was how sumac always grows and brought a piece to our new house. For years it behaved and then suddenly it has decided to take over. Mowing it is not stopping it's advance, I have tried pulling it but now realize any little piece will grow. I believe my pulling is just encouraging it to branch out more underground. Do you think your cardboard cover would work?

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    1. I have struggled with Sumac as well, so I can relate to your problem.
      I do not think smothering the area with cardboard would work. I am amazed at how far those fresh shoots appear to travel! You'd therefore have to cover a huge area with cardboard to have it be effective.
      If you don't mind using a chemical solution, watch this Garden Answer video:https://www.youtube.com/watch?v=Mto5nGnQHR4
      If you find a fresh shoot, you could cut it off and treat it as Laura does in the video with the Stump and Vine killer. The good thing about this product is it is very targeted.
      If you are at all worried about using chemicals, take heart. We removed our tree years ago and it still sends up the odd shoot. I try to get them when they are small and yank out as much of the root as possible. Every year there are less of them.

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