Sweet leaf, Stevia rebaudiana, a natural sweetener. Close up showing serrated leaves.

Sweet leaf, Stevia rebaudiana, a natural sweetener. Close up showing serrated leaves.

Sweet leaf, Stevia rebaudiana, a natural sweetener. Close up showing serrated leaves.

Sweet leaf, Stevia rebaudiana, a natural sweetener. Close up showing serrated leaves.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of single flower head, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of single flower head, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of flower heads, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of single flower head, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of flower heads, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of single flower head, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of single flower head, selective focus.

Rose root, Rhodiola rosea, used in herbal medicine. Close up of flower heads, selective focus.