Weed killers, chemicals and excavation methods explained by the specialists.
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What works
The most effective over-the-counter herbicides are glyphosate-based weed killers such as:
- Roundup
- Gallup
- Landmaster
- Rodeo
- Touchdown
These are known as translocated herbicides, which means they are absorbed by the leaves and carried down into the roots. This is essential when treating knotweed, as surface treatments alone will not reach the underground rhizomes.
For best results:
- Apply in late summer or early autumn, when the plant naturally draws nutrients into its roots
- Repeat applications annually over at least three to four growing seasons
- Apply to healthy, leafy growth, not recently cut stems
What doesn’t work
Many DIY products fail because they are contact-only weed killers, which damage only the visible parts of the plant. These can make it seem like the problem is solved while the root system continues to thrive underground.
And despite what you might read online:
- Bleach, vinegar, and salt do not kill Japanese knotweed
- These substances may damage your soil and garden but will not prevent regrowth
“I tried the shop-bought stuff for years. Nothing worked until I called these guys.” - Lisa, Oxford
Herbicides not getting the job done?
A Precise Alternative: How Stem Injection Works
In situations where spraying is not ideal, such as in gardens, near water, or around valuable plants, stem injection offers a more targeted way to treat Japanese knotweed.
Instead of applying herbicide across the entire plant, this method involves injecting a concentrated dose directly into each stem. The treatment reaches the root system without affecting surrounding vegetation.
When stem injection is useful
- In residential gardens with other plants nearby
- Close to ponds, water features or drainage channels
- In areas where discretion or reduced chemical spread is important
- For small infestations with fewer stems to treat
This technique typically requires fewer applications than spraying, especially when timed in late summer or early autumn.
Concerned about treating knotweed near water or your garden plants?
When Digging Up Knotweed Is the Only Option
In some situations, no amount of spraying or targeted treatment will be effective. When the land is being developed or when time is limited, digging out the knotweed completely becomes the most reliable solution.
This approach involves excavating all soil that contains rhizomes and arranging for its proper disposal. It is the fastest way to remove knotweed from a site, but it is also the most disruptive and labour-intensive.
When excavation is considered:
- If the area is due to be built on or landscaped soon
- If there is a tight timeline, such as before a property sale or development
- When other treatment methods have not worked
- For infestations near foundations, drainage or utility lines
It is important to understand that even a tiny piece of root material, as small as 0.2g, can regrow. This makes full excavation very difficult to manage without the right equipment and knowledge of safe disposal procedures. For those who want guaranteed results, professional Japanese knotweed removal is often the best option.
Planning to develop or sell land affected by knotweed?
Using Root Barriers to Contain Japanese Knotweed
Sometimes, the goal is not complete eradication but preventing the spread of knotweed into neighbouring land. In these cases, a root barrier may help contain the underground rhizomes and limit the risk of future damage.
A root barrier is a physical membrane installed vertically in the soil. Since Japanese knotweed rhizomes rarely grow deeper than two metres, barriers are typically placed at a depth of around three metres to block the roots completely. This approach may be considered where full removal is not immediately possible or where development plans are still in progress.
When to consider a root barrier:
- As a temporary measure to stop knotweed spreading into other areas
- When immediate removal is not viable due to cost or timing
- To protect boundary lines, buildings, or neighbouring properties
- In combination with other long-term treatment methods
Root barriers are not a solution for killing knotweed, but they can help prevent it from becoming a larger problem.
Need help containing knotweed before it spreads to neighbouring land?
Stop trying to kill Japanese knotweed yourself!
Did you know knotweed can regrow with only a thumbnail’s worth (around 0.2g) of its root system left in the soil?
We can help provide a solution that lasts.
What Happens If You Don’t Kill Japanese Knotweed?
Leaving Japanese knotweed untreated can cause more than just inconvenience. Over time, it can lead to structural damage, legal issues, and reduced property value.
Here are some of the most common risks:
Damage to buildings and infrastructure
Knotweed rhizomes can grow through small cracks in concrete, tarmac, patios and even pipework. Left alone, the plant can exploit weaknesses in foundations and underground structures.
Legal liability
If knotweed spreads from your land onto neighbouring property, you could be held responsible. In some cases, this can result in legal action or fines.
Mortgage problems
Lenders often take a cautious view of properties affected by knotweed. It can result in mortgage refusals, reduced valuations, or additional conditions before approval.
Increased cost of removal
The longer knotweed is left to grow, the larger and deeper the infestation becomes. This can increase both the cost and complexity of removal later on.
Worried about knotweed damaging your home or affecting your sale?
Stop trying to kill Japanese Knotweed yourself!
We can help provide a solution that lasts.
Frequently Asked Questions
Can I kill Japanese knotweed myself?
What is the best time of year to kill Japanese knotweed?
Will Japanese knotweed die in winter?
How long does it take to kill Japanese knotweed?
Does vinegar, salt or bleach work on Japanese knotweed?
Is it illegal to have Japanese knotweed on my property?
Can you just cut down Japanese knotweed to get rid of it?
Get Rid Of Japanese Knotweed Today
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