Phytostabilisation: locking a contaminant into the soil instead of harvesting it
In short
Phytostabilisation pursues the opposite of phytoextraction: the contaminant should stay where it is and specifically not move into the plant. Vegetation binds it to roots and root exudates, holds the soil in place and so narrows the path towards groundwater. The site does not get cleaner, it gets quieter.
When that is the better question
On many contaminated sites the pressing problem is not the concentration in the soil but the discharge out of it. Around 1700 hectares of farmland in the Mittelbaden and Mannheim areas hold a large reservoir of poorly mobile PFAS precursor compounds, from which mobile compounds keep seeping towards groundwater for decades if nothing is done. So far this is stopped there by local excavation or by sealing the surface, which means diggers and concrete. Planting that slows the same path would be the cheaper answer to the same question.
The distinction from extraction is not academic: one strategy wants mass taken off the site, the other wants movement prevented. Claiming both at once means one of them has not been measured.
What is documented and what is not
The only peer-reviewed field trial with hemp on PFAS-contaminated soil did not test this effect. Its authors note that additional binding through sorption to roots and root exudates is conceivable, but has not been studied for hemp specifically. That leaves the benefit standing as a possibility rather than a finding. For heavy metals a 2023 review reaches a comparable picture: most trials ran in greenhouses, and practical assessments from the field are missing.
Link to cannabis
For growing, the distinction matters in practice. A stand of industrial hemp on contaminated land removes measurably little from the soil, but keeps it covered and rooted. Whether that genuinely reduces leaching towards groundwater is open for this crop. What hemp demonstrably does, namely store substances in leaf and stem, is covered in the article on contaminant uptake in hemp.