Japanese knotweed herbicide treatment

At SE Knotweed, herbicide treatment controls Japanese knotweed by applying glyphosate through stem injection and foliar spraying so the plant carries it down to the rhizome across a 3 to 5 year programme. It is the lowest-cost method and suits sites with no sale deadline.

Herbicide treatment costs from around £1,200 to £3,500 across the programme, and we confirm the figure at survey once the stand is measured.

What is herbicide treatment for Japanese knotweed?

At SE Knotweed, herbicide treatment is a planned programme of glyphosate applications that kills a knotweed stand at the root over several growing seasons, rather than the quick knock-back a garden weedkiller gives.

We treat during the active growth window from around May to October, record each visit, and monitor for regrowth until the rhizome is spent. It is the lowest-cost method in the treatment schedule and suits gardens with no sale deadline. Get in touch to book a survey.

How do stem injection and foliar spraying work?

We apply glyphosate two ways depending on the site. Stem injection puts a measured dose directly into each hollow cane, which is precise and used near ponds, planting or a neighbour's boundary where drift matters.

Foliar spraying coats the leaves across a larger, open stand and is quicker where there is nothing sensitive nearby. Both routes move the herbicide into the rhizome, and we choose the method, dose and timing to the stand rather than spraying blind.

How long does a herbicide programme take?

A herbicide programme runs across 3 to 5 growing seasons, with one to three treatment visits a year and a monitoring visit to confirm the rhizome is dying back. The exact length depends on the size and age of the stand and how it responds.

Where a sale is in progress, the management plan and insurance-backed guarantee are usually enough for a lender well before the programme finishes.

How much does herbicide treatment cost?

Herbicide treatment costs from around £1,200 to £3,500 across the whole programme for a domestic stand, driven by the size of the stand, the number of visits and access. It is the lowest-cost method because the soil stays in place and there is no disposal.

We measure the stand at survey and give a fixed programme price, so please read these as indicative. The cost pillar compares it with excavation.

Is herbicide treatment guaranteed?

Herbicide treatment by an audited specialist is backed by an insurance-backed guarantee that commits to further treatment at no cost if regrowth appears within the term. It is the same document a mortgage lender accepts.

Because the rhizome is killed in place rather than removed, the monitoring period and aftercare matter, and the guarantee covers the site through it.

When is herbicide the right choice over excavation?

Herbicide is the right choice when there is no building work or sale deadline forcing the pace, when the soil can stay on the plot, and when cost is the priority. Excavation is faster but far more expensive because of the soil disposal.

If you need the ground clear in days for a development, excavation or a combination approach fits better, and we set out the trade at survey.

Common questions

Does glyphosate kill Japanese knotweed in one go?
No. One application weakens the plant but does not kill the rhizome. A monitored programme over 3 to 5 seasons is needed, which is why the work carries an insurance-backed guarantee.
Can I still build on treated ground?
Treated ground can hold living rhizome for some time, so where you plan to build we usually recommend excavation instead. We advise on this at survey.

Book a survey and get a costed plan

Tell us the address and what a surveyor flagged. We confirm the plant, record the RICS category and set out the figures.

Book a survey
Call 01924 944600