| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Commiphora wightii | Inflorescence | -- | -- | Jim Duke's personal files. | |
| Coptis chinensis | Rhizome | 11.0 | 17.0 | 1.4 | * |
| Coptis spp | Rhizome | 11.0 | 17.0 | 1.4 | * |
| Coptis japonica | Rhizome | 11.0 | 17.0 | 1.4 | * |
| Coriandrum sativum | Fruit | 10.0 | 13.0 | 0.0 | * |
| Coriandrum sativum | Leaf | -- | 18.0 | -0.3 | USDA's Ag Handbook 8 and sequelae) |
| Cornus officinalis | Fruit | 5.0 | 6.0 | -0.5 | * |
| Corylus avellana | Seed | 13.0 | 82.0 | 6.1 | * |
| Crataegus laevigata | Fruit | -- | -- | * | |
| Crataegus laevigata | Flower | -- | -- | * | |
| Crataegus cuneata | Fruit | -- | 8.0 | -0.4 | * |
| Crocus sativus | Silk Stigma Style | -- | 3.0 | USDA's Ag Handbook 8 and sequelae) | |
| Cucumis melo | Fruit | 0.4 | 7.7 | -0.4 | * |
| Cucumis sativus | Fruit | 0.3 | 42.0 | 2.3 | * |
| Cucurbita pepo | Seed | 14.0 | 25.0 | 0.9 | * |
| Cucurbita maxima | Leaf | 4.2 | 30.0 | 0.1 | * |
| Cucurbita spp | Fruit | 0.7 | 12.0 | -0.1 | * |
| Cuminum cyminum | Seed | 9.0 | 16.0 | 0.1 | * |
| Cuminum cyminum | Fruit | 9.0 | 16.0 | 0.2 | * |
| Curcuma longa | Rhizome | 6.0 | 17.0 | 1.4 | * |