Ordinary plants have a strict tolerance ceiling for heavy metals — once root uptake pushes internal metal concentration past that limit, the metal poisons cellular machinery and the plant stunts or dies, so it extracts very little before shutting down. Hyperaccumulators evolved metal-binding proteins and vacuolar compartmentalization that safely sequester metal away from sensitive organelles, letting them tolerate and actively accumulate concentrations 100–1000× higher without harm.
Each cycle: plant → grow (roots draw metal ions from soil into tissue, visibly color-coding from green to yellow to orange as tissue load rises) → harvest (biomass — and the metal locked inside it — is removed before it can decompose and re-release the metal). Repeating this progressively draws down total soil concentration. Because each plant can only pull a bounded fraction of what's present, severely contaminated soil needs many repeated cycles, not one planting.
- Hyperaccumulator — high per-cycle extraction, tolerates high tissue load, stays healthy.
- Ordinary plant — low uptake ceiling; in heavily contaminated soil it visibly wilts/stunts and extracts comparatively little.
- Cycles to target — estimated from the current extraction rate and remaining contamination above your cleanup threshold.