| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Caesalpinia pulcherrima | Flower | -- | -- | * | |
| Calendula officinalis | Plant | -- | -- | * | |
| Camellia sinensis | Plant | -- | -- | * | |
| Camellia sinensis | Leaf | -- | 10000.0 | -0.2 | * |
| Camellia sinensis | Shoot | -- | -- | * | |
| Camptotheca acuminata | Leaf | -- | -- | * | |
| Capparis spinosa | Flower | -- | -- | * | |
| Capsicum frutescens | Fruit | -- | 63.0 | -0.5 | Pizzorno, J.E. and Murray, M.T. 1985. A Textbook of Natural Medicine. John Bastyr College Publications, Seattle, Washington (Looseleaf). |
| Carum carvi | Leaf | -- | -- | * | |
| Carum carvi | Seed | -- | -- | * | |
| Carum carvi | Fruit | -- | -- | * | |
| Carum carvi | Flower | -- | -- | * | |
| Castanea sativa | Bark | -- | -- | * | |
| Castanea sativa | Wood | -- | -- | * | |
| Castanea sativa | Leaf | -- | -- | * | |
| Catharanthus roseus | Plant | -- | -- | Rizk, A.F.M., The Phytochemistry of the Flora of Qatar, Scientific and Applied Research Centre, University of Qatar, Kingprint, Richmond, UK, 1986. | |
| Cedrus deodora | Stem Bark | -- | -- | * | |
| Ceiba pentandra | Leaf | -- | -- | * | |
| Centaurea cyanus | Shoot | -- | -- | Jim Duke's personal files. | |
| Centaurea calcitrapa | Plant | -- | -- | * |