Quackgrass removal questions - Ask Extension
We have a 20' x 30' garden with heavy quackgrass infiltration (has spread & grown to 2+ feet) with various bushes, vegetables and floiwers. We h...
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Quackgrass removal questions #930208
Asked April 30, 2026, 5:27 PM EDT
We have a 20' x 30' garden with heavy quackgrass infiltration (has spread & grown to 2+ feet) with various bushes, vegetables and floiwers. We handpicked all out (so short) but did not remove roots so need to act now. We do not want to use chemicals. We know not to use tiller. The U of MN article on Quackgrass was informative - but not helpful on how to actually manage.
Questions:
1. We are going to dig out. What is your advice on what to do (and what not to do)?
2. How far should I dig down?
3. Should I dispose of a fair amount of dirt as I work to extract roots, or just dispose of the roots?
4. What is MOST effective way to cover the ground after I have attenpted to remove all grass and root system (to reduce how fast and broadly it grows back). Should I rely on Landscape fabric? Is cardboard more effective? How much mulch should be put on top?
5. Is it necessary to fertilize the soil after I remove the Quackgrass?
See attached pictures. Thank you!
Ramsey County Minnesota
Expert Response
To clear quackgrass without chemicals, you'll need to remove the entire root system and smother any survivors:
For your questions:
For your questions:
- Use a garden fork and not a spade or tiller to lift the soil and pull out the long, white rhizomes intact. Try to get all of the the rhizomes and avoid chopping them into pieces.
- If you dig 6 - 8 inches deep you'll find the majority of the root network.
- Keep the soil, but you need to eliminate the roots. Bag them or dry them in the sun until they are brittle. Do not put them in a compost pile as they may regrow.
- You can use overlapping cardboard which is more effective than fabric. Top this with 3 - 4 inches of mulch.
- Don't fertilize now because nitrogen can boost regrowth of any missed roots. Add any compost only when you are ready to replant.
Thank you for your insights to my earlier submission. I have nearly completed the quackgrass removal and soon will be pivoting to replanting the garden with new placement of the perennials (many are currently planted in holding spots only). I have 5 additional questions (see below and the attached photos).
Quick Update on Circumstances:
- Large area (perhaps 25' x 35') dedicated to a flower garden
- Had been infiltrated by quackgrass.
- Have physically been removing quackgrass including roots and rhizomes (did not want to use chemicals)
- I recovered several perennials (sometimes having to extract quackgrass out of their roots) - hosta, iris, hibiscus, daylillies, native grass, fern, peony, succulent, sage, etc.
- Area gets several hours of direct sunlight
- 2 photos attached to this email
My Questions:
[1] What is the best way to place the cardboard to get max protection yet allow perennials to thrive --- (a) cover entire area first (I gathered enough cardboard to do) then cut holes to plant the flowers, or (b) plant all the plants first then cut cardboard to fill in between the flowers (seems harder perhaps), or (c) a different approach?
[2] What is the right diameter of an opening around each perennial to maximize protection yet ensure they have room to grow? For example, do I leave 3" extra around current perennial size?
[3] Does the type of perennial affect size of opening (ie spreading vs not spreading)?
[4] Do I cover both the cardboard and the exposed dirt right up to the perennial with mulch?
[5] Do you have any other advice on how I should be reestablishing the garden in these circumstances?
Thank you!
[4] Do I cover both the cardboard and the exposed dirt right up to the perennial with mulch?
[5] Do you have any other advice on how I should be reestablishing the garden in these circumstances?
Thank you!
-------- Original message --------
From: Ask Extension
Date: 5/1/26 5:40 PM (GMT-06:00)
To: pkstore
Subject: Re: Quackgrass removal questions (#0200123)
Your garden will be lovely once it's all finished! The best approach for placing cardboard is usually to place it first over the cleared soil, then cut openings for the plants and mulch the whole surface, rather than trying to weave cardboard around each plant. This should give the best weed suppression. Very thick cardboard layers can restrict water and air movement, so just lay down 1–2 layers. keep the cardboard back about 1–2 inches from the stem or crown for most plants and cover both the cardboard and the exposed soil, but do not mound mulch right up against the crown of each perennial. Monitor the beds and pull any quackgrass as soon as you see it. Good luck with your project.
