Horsetail is an invasive weed that can cause a lot of damage and disruption in British gardens.
Although it’s not an unattractive plant, horsetail has fast-growing underground stems which let it spread quickly and take deep hold, making it difficult to keep under control.
We’ve written this guide for people facing a horsetail infestation.
Our hope is that the information here will help you to get things under control again!
What Is Horsetail?
Firstly, it’s important to know that while horsetail and mare’s tail are often used interchangeably, they’re actually two distinct plants.
- Horsetail is Equisetum arvense, a perennial plant that grows on land.
- Mare’s tail, on the other hand, is Hippuris vulgaris, an aquatic plant.
Horsetail is native to arctic regions and parts of the northern hemisphere.
It’s actually considered a “living fossil” given that its relatives are estimated to have occupied the Earth around 350 million years ago! [source]
This perennial weed forms dense clusters of dark green foliage that can take resources and nutrients from other plants, causing damage.
One of the main reasons the plant is so hard to control is that the roots (or rhizomes) can penetrate up to two metres below the ground! Far out of reach of most herbicides.
The plant reproduces through its rhizome network or through spores, both of which make it tricky to control. [source]
When you’re dealing with a plant that can reproduce through sections of root that have been cut, it becomes more difficult to remove the plant entirely from your garden.
Why Is Horsetail Problematic?
To be considered a weed, a plant must be unwanted, hard to keep at bay, and in competition with desired plants for the resources and nutrition available in your garden.
Horsetail ticks all of these boxes with vigour.
Once established in your garden, horsetail has a tendency to crowd out other plants.
Then, even when you cut it back or attempt to uproot it, there are rhizomes waiting deep underground, far out of reach, ready to rear their heads once again. [source]
Not only that: Because this plant burrows so deep, it’s able to spread between gardens far underground, beneath even the deepest of fences.
In short, there’s good reason that horsetail is known as one of the most fearsome weeds we face in the UK!
How To Identify Horsetail
The first step in controlling and killing horsetail is making sure that you’re actually dealing with horsetail:
- Horsetail grows anywhere from 0.1 to 1 metres in height.
- The plant is characterised by side shoots that branch out from segment joints, and by spore cones with a distinctive brown colouration.
- These cones are about half a centimetre in diameter.
How To Control Horsetail
If you’re unfortunate enough to have a horsetail infestation, you have a few options.
Note that some UK councils have reporting programs in place to monitor the presence and spread of horsetail in the local area.
If you live in a place whose council collects this information, make sure to let them know. [source]
They may even be able to provide information or help with controlling the spread.
1) Removing Shoots
The temptation when you see horsetail popping through the ground may be to cut it back.
Try to resist this, if possible. Because of the deep underground rhizome network, cutting back at ground level can cause more harm than good, as cut segments can regrow into more weed, effectively compounding the problem.
The Royal Horticultural Society (RHS) note that over a period of many years, trimming back surface-level horsetail may lower the severity of an infestation.
However it’s not ideal as a solution in the short or long-term.
2) Mulch The Area
Regular mulching is associated with reduced levels of horsetail, although as with removing shoots, this must be done on a long-term basis to deliver optimum benefits.
3) Mow Any Horsetail In Your Lawn
If you see horsetail coming through your lawn and you haven’t yet arranged a method to remove it completely, you can prevent it from growing too large by mowing regularly.
This is definitely a measure designed to control, rather than remove horsetail, though.
4) Digging Up As Much As Possible
While you’ll never remove an entire plant once it’s fully established, you can weaken growth by repeatedly digging up as much as you can reach.
The damaged underground roots will most likely sprout again and pop back up, making this something like a game of whack-a-mole, but you may be able to curtail the worst of the growth.
5) Consider The Use Of Weed Killer
Horsetail will respond to treatment with weed killer, but the deep rhizomes may cause problems still more.
Unlike some weeds which can be eradicated in one year through the correct application of weed killer, horsetail may require a prolonged campaign spanning several years.
Each successive treatment is likely to further weaken the rhizome network, with the cumulative damage hopefully offsetting any recovery the plant is able to achieve between treatments.
Here are some things to bear in mind when using weed killers to control horsetail –
- Bruise the roots of the plant first to weaken the membrane and encourage higher absorption of weed killer. This will help the weed killer to reach more of the plant, and to cause more damage.
- Try to use a weed killer that won’t damage surrounding grasses. This will encourage grass to spread into the area recently vacated by horsetail, increasing the amount of competition and reducing its ability to re-establish itself.
With such a fearsome reputation, there are a lot of questions and a lot of misinformation around horsetail.
In this section we’ll address a couple of these questions, to make sure you’re working with the very best information.
Can vinegar kill horsetail?
No, vinegar cannot kill horsetail.
This is quite possibly an old wives tale, but sadly it’s not one of the ones that holds truth.
Horsetail is so vast and sprawling that the mild acidity of vinegar is nowhere near enough to cause the level of damage required to kill the plant.
Can you dig up an entire horsetail?
While it’s theoretically possible to dig up horsetail, the amount of work required almost certainly renders this option unsuitable.
The rhizomes of the plant spread out far and wide underground, up to depths of around two metres, meaning that you’d have to dig up an enormous amount of soil to get anywhere close.
And that’s not taking into account outward growth – potentially reaching into other gardens, under structures, and so on.
Unless you’re planning to excavate your entire garden and start again from scratch, we really don’t recommend considering this option.
Should you trim horsetail?
Although trimming horsetail back won’t do anything about the underground part of the problem, the technique can be used to keep the plant in check.
Horsetail grows fairly quickly so you may find yourself doing this quite often, but it’s a good way to protect against unruly horsetail above the ground.
Dealing With Horsetail
There you have it: The best ways to protect against the further spread of an existing horsetail problem.
This is an unruly and frustrating weed, and is renowned for being difficult to remove completely.
For this reason, most of the measures above have the goal of curtailing ongoing growth, and reducing the amount of horsetail visible above the ground.
If you’re unlucky enough to have horsetail in your garden, we wish you the best of luck in getting things under control.