| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Carica papaya | Seed | 12650.0 | 13282.0 | -0.3 | * |
| Carica papaya | Leaf | -- | -- | Jim Duke's personal files. | |
| Carthamus tinctorius | Seed | 2000.0 | 6260.0 | -0.4 | * |
| Carum carvi | Plant | 1100.0 | 1221.0 | -0.3 | * |
| Carum carvi | Seed | 1000.0 | 1800.0 | -0.5 | * |
| Carya illinoensis | Leaf | -- | -- | * | |
| Cassia tora | Seed | 2508.0 | 5624.0 | -0.4 | * |
| Caulophyllum thalictroides | Root | -- | -- | Jim Duke's personal files. | |
| Cedrus deodora | Seed | -- | 37995.0 | 0.3 | * |
| Ceiba pentandra | Seed | 4000.0 | 32000.0 | 0.1 | * |
| Centaurea calcitrapa | Plant | -- | -- | * | |
| Centaurium erythraea | Plant | -- | -- | * | |
| Centella asiatica | Plant | -- | -- | * | |
| Ceratonia siliqua | Seed | 200.0 | 1820.0 | -0.5 | Wealth of India. |
| Chamaelirium luteum | Rhizome | -- | -- | Jim Duke's personal files. | |
| Chrysanthemum x morifolium | Flower | -- | -- | Wealth of India. | |
| Cicer arietinum | Seed | 850.0 | 960.0 | -0.5 | USDA's Ag Handbook 8 and sequelae) |
| Cichorium intybus | Leaf | 10.0 | 204.0 | -0.5 | USDA's Ag Handbook 8 and sequelae) |
| Cichorium endivia | Leaf | 20.0 | 322.0 | -0.4 | * |
| Cichorium intybus | Plant | -- | -- | * |