| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Cucumis melo | Fruit | 0.4 | 7.7 | -0.4 | * |
| Crocus sativus | Silk Stigma Style | -- | 3.0 | USDA's Ag Handbook 8 and sequelae) | |
| Crataegus laevigata | Flower | -- | -- | * | |
| Crataegus cuneata | Fruit | -- | 8.0 | -0.4 | * |
| Crataegus laevigata | Fruit | -- | -- | * | |
| Corylus avellana | Seed | 13.0 | 82.0 | 6.1 | * |
| Cornus officinalis | Fruit | 5.0 | 6.0 | -0.5 | * |
| Coriandrum sativum | Leaf | -- | 18.0 | -0.3 | USDA's Ag Handbook 8 and sequelae) |
| Coriandrum sativum | Fruit | 10.0 | 13.0 | 0.0 | * |
| Coptis japonica | Rhizome | 11.0 | 17.0 | 1.4 | * |
| Coptis chinensis | Rhizome | 11.0 | 17.0 | 1.4 | * |
| Coptis spp | Rhizome | 11.0 | 17.0 | 1.4 | * |
| Commiphora wightii | Inflorescence | -- | -- | Jim Duke's personal files. | |
| Colocasia esculenta | Leaf | -- | 1.5 | -0.7 | * |
| Colocasia esculenta | Root | 1.6 | 8.0 | -0.4 | * |
| Coix lacryma-jobi | Seed | -- | 5.0 | -0.9 | Suziki, A., Morimoto, I., and Okitzu, T., Elution of Metals from Crude Drugs, Shoykugaku Zasshi 36(3):190-195. |
| Cocos nucifera | Seed | 3.2 | 33.0 | 1.6 | * |
| Cnidium officinale | Rhizome | -- | 9.0 | -0.3 | * |
| Citrus reticulata | Fruit | -- | 4.8 | -0.6 | * |
| Citrus paradisi | Fruit | -- | 7.7 | -0.4 | * |