Stem injection vs foliar spray: which herbicide method actually works best?
Two professional techniques, two different jobs. The science, the costs, and which one we'd choose for your site.
Glyphosate is the only herbicide we have that reliably exhausts a Japanese knotweed rhizome over a 3–5 year programme. How we deliver it matters as much as the chemical itself.
Stem injection
A measured 2 ml dose of concentrated glyphosate is injected into each hollow cane below the second node, using a calibrated injector. The chemical translocates down through the vascular tissue into the rhizome with almost no off-target loss.
Best for
- Domestic gardens with ornamentals close by.
- Sites near ponds, ditches and watercourses (no spray drift).
- Stands of 200 stems or fewer.
Foliar spray
Knapsack or vehicle-mounted application of a dilute glyphosate solution onto the full leaf canopy in late summer, when the plant is actively translocating sugars into the rhizome. Coverage matters more than volume.
Best for
- Large open stands on development land, railways, riverbanks.
- Sites with no sensitive vegetation within 5 metres.
- Programmes where speed of application matters more than precision.
What we usually recommend
On a domestic garden, stem injection nearly always wins on safety alone — no risk of killing your magnolia. On a 2-acre former industrial yard, spray is the only sensible answer. The honest middle ground is to inject the perimeter and spray the interior; we do this regularly on mixed sites.
Frequently asked questions
- Is stem injection more effective than spray?
- Per-stem, yes — virtually 100% of injected glyphosate reaches the rhizome, versus around 30% from foliar spray. But spray covers far more ground per hour, so for large open stands it remains the right tool.
- Can I do stem injection myself?
- No. Concentrated glyphosate above 360 g/L is an industrial-use product requiring PA1 and PA6AW certificates and approved injection equipment. Doing it without the certificates is an offence under the Plant Protection Products (Sustainable Use) Regulations.
Reviewed by
The survey team
PCA-certificated surveyors, Japanese Knotweed Elimination
PA1 / PA6A certificated surveyors who carry out the site visits, write the management plans and sign off the reports issued to lenders and solicitors.
Reviews the technical, legal and lender statements in this article.
What this page can't tell you
- Guidance is general. Identification, treatment choice and timescales can only be confirmed by a site visit — photographs alone are indicative.
- Lender and insurer requirements vary by institution and change over time. We state what is typically accepted, not what any named lender will accept on your case.
- Guarantee (IBG) eligibility depends on the plan chosen, the survey findings and the underwriter's acceptance. It is not automatic.
- Legal points summarise published law and guidance current at the review date. They are not legal advice.
Last reviewed · Questions on anything stated here: 07582 869979
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