Dealing with couch grass is a problem that most gardeners and allotment holders will have to face at one time or another.
This common weed can not only be invasive, it also prevents seeds from other plants germinating. It looks like a normal grass on the surface, but it’s underground that the problems get real. The roots form a dense, almost impenetrable barrier. It spreads in a number of ways, root division, runners and occasionally by seed.
Couch Grass Spreads Rapidly
All it takes is one extremely small section of the white rhizome to lay on top of the soil for couch grass to start to grow. Once it starts growing, it spreads very quickly. Then it will send runners above the surface and endless roots below ground.
Those roots soon become entangled together to create enormous networks of tight clumps of roots. These roots get wrapped around any other plants including herbaceous plants, fruit bushes and trees, bulbs, or any plants growing in close proximity.
How Does Couch Grass Get Into Your Garden?
All it takes is the tiniest piece of root and before long your garden will be covered with couch grass. Often couch grass root can be spread by using manure, or compost that hasn’t been broken down properly. If your neighbours have couch grass it will spread under the fence and before long you’ll have it too.
How To Control Couch Grass
The first thing to consider is whether you can control couch grass by non chemical means. Not only is this better for your garden and the environment, but it is also the least expensive way of controlling the spread of couch grass. Non chemical methods are time consuming and if the couch grass has had time to establish, it’s also a thankless task.
It’s almost impossible to remove every last piece of that white, fragile rhizome, and it takes a piece so minute to grow into a new plant that just by disturbing it you will have spread it.
Non Chemical Means Of Controlling Couch Grass
If the area affected is uncultivated, and the soil is light, working it over with a fork will remove most of the larger root systems of couch grass. However, it is so easy to leave a small piece that will soon regrow, so you’ll need to be clearing for weeks if not months.
Another effective method on uncultivated areas is to cover the area completely with cardboard and black plastic to starve the roots of any light. This is not a short term solution as the roots can remain inactive in the soil for many months.
If the area is cultivated, hand weeding is the only option, this is best done in early Springtime when any plants will soon re-establish themselves and bulbs are dying off. Roses, trees and shrubs can get their roots damaged easily and as couch grass entangles itself in among the roots of other plants this can be seriously problematic.
For lawns, the best plan is to remove infested areas and dig out any remaining couch roots before re-turfing.
Dealing With Couch Grass Using Plants
It is widely accepted by many organic gardeners that sowing turnip seeds will kill couch grass. These two will not mix and the couch grass will wither and die. You will still need to remove every piece of white rhizome that you lift when harvesting the turnips to prevent couch grass regrowing.
Chemical Control Of Couch Grass
If you do have to go down the chemical route to eradicate couch grass, you will encounter a few issues.
- Lawn Weed Killers
There are no selective weed killers that will kill couch grass while allowing the rest of the lawn to grow. - Glyphosate
All glyphosate based weed killers are effective in eradicating couch grass if applied correctly. But they are indiscriminate, and will kill every plant they touch. You will need to protect any other plants with polythene while using glyphosate to prevent any spray drifting onto them.
When To Use Glyphosate
According to the experts, Spring and Autumn are the best times to use glyphosate. Wait until the couch grass is visible and spray being sure to cover the entire area. If you decide to use in Autumn, early October to mid November are the best times.
Results during frosty conditions are sketchy at best, also avoid drought conditions too. If the areas of couch grass are too large, it is best to dig up any cultivated plants. And replace them once the treatment is finished.
Couch grass should die back within three weeks but be on the lookout for any new growth. Remove any new growth as soon as it appears. Don’t replant or try to grow any plants on the treated area until all signs of couch grass have gone.
Does Couch Grass Have Any Uses?
Couch grass is a weed and considered to be a pest by gardeners and allotment holders here in the UK. In other parts of the world it is actively used to bind soil together and prevent erosion. Couch grass is also used as a primary food source for cattle and other livestock.
Why Is Couch Grass A Problem For Gardeners?
Couch grass begins growth very early in the growing season, this means it can smother many other plants before they have a chance to get established. Couch grass also absorbs many nutrients from the soil depleting the soil’s goodness and preventing later plants from obtaining any.
Phytotoxins
The roots of couch grass secrete acids and other phytotoxins directly into the soil. These prevent surrounding plants from absorbing many nutrients from the soil. This affects any plants growing near to couch grass growth but is also still present once couch grass has been removed.
Which is why the glyphosate and blocking light methods are somewhat ineffective in controlling couch grass. It actually produces conditions best suited for its own growth. Whilst creating poor conditions for other plants. As the couch grass plants decompose, they are still secreting phytotoxins that damage new plants and prevent healthy growth.
These phytotoxins tend to remain in the soil for up to four weeks after the couch grass has completely died. However, this is a mute point really because couch grass roots can be as deep as 8 inches and spread for up to 2 feet. Plus they spread in every direction which makes them almost impossible to completely eradicate.
Couch Grass Facts
Couch grass (Elymus repens) is a perennial plant that grows in Europe, Asia, The Artic and Northwest Africa. It can reduce crop yields by up to 95% according to the Pennsylvania State University[1]. It is possible to manage couch grass by combining chemical and non chemical preventative measures.
Under good growing conditions a patch of couch grass is able to spread 6 feet in diameter each growing season. Good growing conditions include;
- Wet
- Dry
- Acid Soils
- Alkaline Soils
- Salty Soils
The only sure way to prevent couch grass from spreading is to remove as much as possible (including roots). Completely blocking any light at all. Couch grass is able to grow in temperature ranges of 2c to 35c (36f to 95f). New shoots above ground can be killed by frosts but as there is usually enough root system below ground this is soon replaced.
A good way to prevent couch grass from taking over is by use of grazing animals (not exactly practical for us gardeners). it spreads primarily through root division but is known to flower from mid June through to mid August in the Northern hemisphere. The seeds can remain dormant in the soil for up to 3 years.
Other names include;
- Twitch
- Quick Grass
- Dog Grass
- Quack Grass
- Scutch Grass
- Quitch Grass
- Common Couch
To completely eradicate couch grass you will need to completely remove all light. This is only possible using something strong and thick like wood or concrete. Couch grass is capable of growing through plastic weed membranes for example.
