Bacopa (Bacopa monnieri)

Ashwagandha (Withania somnifera), sometimes called “Indian ginseng,” is a sturdy shrub growing to about 5 ft (1.5 m) with oval leaves, greenish or yellow flowers, and small, round fruits. NCCIH says some preparations may help insomnia and stress, but there isn't enough evidence to know whether it helps most other conditions.

Black pepper is a perennial woody climbing vine growing to about 16 feet, with large oval leaves, spikes of small white flowers, and clusters of small round fruits that ripen from green to red. Native to southwestern India and now cultivated in tropical areas worldwide, the fruit is harvested from plants that are at least three years old. Different processing methods yield green, black, red, and white peppercorns, each with distinct flavors and uses. Cultivated as both a spice and medicine since ancient times, pepper was such a prized commodity in world trade that Attila the Hun reportedly demanded 3,000 pounds of it as ransom during his siege of Rome in 408 CE.

Calendula (Calendula officinalis) has bright orange daisy-like flowers.

California poppy (Eschscholzia californica) is an annual or short-lived perennial with finely divided leaves and vibrant orange, yellow, pink, or red blossoms. It is related to the opium poppy.

Cat's claw is a climbing vine that can grow to 100 feet or more, with stems up to 8 inches in diameter, large glossy leaves, and sharp hooks resembling a cat's claws. Native to tropical rainforests in the central and eastern Andes, especially Peru, Ecuador, and Colombia, it has also been found in Guatemala, Costa Rica, and Panama. Indigenous people of the Amazon rainforest have used cat's claw for centuries to ward off disease, and NCCIH says it is promoted today for osteoarthritis, rheumatoid arthritis, cancer and viral infections. NCCIH says there is no conclusive evidence from studies in people to support cat's claw for any health purpose. By the early 1990s, over-collection from the wild threatened the species' survival; only sustainably sourced stem bark should be used, rather than root bark.

Codonopsis is a small twining perennial growing to 5 feet with oval leaves and pendulous green and purple bell-shaped flowers marked with purple in summer. Native to northeastern China and growing throughout the region, especially in the Shanxi and Szechuan provinces, it is propagated from seed in spring or autumn, and the root is harvested in autumn once the aerial parts have died down. Codonopsis holds a central place in Chinese herbal medicine.

Coltsfoot is a perennial herb growing to 12 inches with flowering stems covered in purple scales, yellow-gold flowers, and heart-shaped leaves. Indigenous to Europe and northern Asia and naturalized in North America, it is commonly found along roadsides, on verges, and in open areas. The flowers are gathered in late winter, and the leaves in summer.

For many people the scent of eucalyptus conjures up days spent in bed during childhood with eucalyptus and other oils smothered on the chest. Eucalyptus is a common ingredient in many over-the-counter cold remedies.