| Plant | Low PPM | High PPM | StdDev | *Reference | |
|---|---|---|---|---|---|
| Echinacea purpurea | Leaf | -- | -- | Jim Duke's personal files. | |
| Echinacea purpurea | Flower | -- | -- | Jim Duke's personal files. | |
| Echinacea purpurea | Root | -- | -- | Jim Duke's personal files. | |
| Echinacea purpurea | Stem | -- | -- | Jim Duke's personal files. | |
| Echinacea angustifolia | Root | -- | -- | Jim Duke's personal files. | |
| Echinacea angustifolia | Stem | -- | -- | Jim Duke's personal files. | |
| Echinacea angustifolia | Leaf | -- | -- | Jim Duke's personal files. | |
| Echinacea angustifolia | Flower | -- | -- | Jim Duke's personal files. |