Amaranthus: Not Just a Weed

Published: February 3, 2020

The genus Amaranthus contains many familiar weeds such Palmer and slender amaranth, waterhemp, and prostrate, redroot, and smooth pigweed (Table 1). All are troublesome in gardens and row crops. Certain species of Amaranthus can also be toxic to livestock under dry weather conditions. Nearly 75 species of Amaranthus are known worldwide, which are used for several purposes, including dyes, ornamentals, food, cosmetics, and oils.

Table 1 Common weed species of Amaranthus in Missouri.

The term Amaranthus comes from the Greek word "amarantus," which means everlasting or never-failing flowers and refers to the showy bracts associated with the flowers. The English poet John Milton referred to the "immortal amarant" in Paradise Lost, which describes the colorful, long-lasting nature of the inflorescence. Other poets, including Percy Bysshe Shelley, Samuel Taylor Coleridge, and William Wordsworth also wrote of the unfading amaranth or blood-red inflorescence of this "love-lies-bleeding" plant.

The Native American Hopi tribe extracted and used a red dye extracted from amaranth flowers. The infamous Red Dye No. 2, also known as amaranth, was banned by the Food and Drug Administration in the U.S. in 1976. However, this dye was a synthetic compound not derived from the plant.

Flowering plant of Coral Fountain amaranth.

The dark red inflorescence of Red Spike amaranth.

Ornamental leaves of Amaranthus tricolor.

Coral Fountain, Dreadlocks, Love-Lies-Bleeding, and Emerald Tassels are varieties of A. caudatus. All are annual plants with impressive panicles in the landscape and in dried arrangements. Red Spike, Hot Biscuits, Autumn's Torch, Hopi Red Dye, and Oeschberg are selections of A. cruentus that also have eye-catching inflorescences. In contrast, A. tricolor, commonly known as Joseph's coat or fountain plant, is prized for its colorful foliage. Common varieties of A. tricolor include Perfecta, Illumination, Splendens, and Early Splendor. These ornamentals are commonly started from seed and set outdoors after the last frost (around May 10 in Missouri). Plants are spaced at about 8 to 18 inches apart, depending on the species, in full sun to partial shade. In the fall, seed can be harvested from panicles and saved for planting next year.

Alternatively, A. tricolor Red Callaloo can be grown outdoors as a leafy vegetable with green and burgundy coloration. It thrives in hot, humid weather and is harvested when leaves are young and tender. In the Caribbean, callallo leaves are often used in soup and side dishes. Leafy amaranth is also a staple vegetable crop in Asia and Africa and goes by several names, including bayam, kalunay, chaulai, harive, morung, litoto, etc.

Garnet Red Amaranth is another A. tricolor variety that is grown as a burgundy-colored sprout or microgreen for a colorful addition to salads or side dishes in the U.S. It can be seeded indoors in a potting mix at a spacing of 1/8th to 1/4th inch apart. For watering, mist or sub-irrigate the potting mix to avoid seed loss and place the container or flat in a well-lit area at 65 to 75°F. Sprouts can be harvested in about 5 to 10 days after planting at the cotyledon stage, or young leaves are harvested for microgreens in about 12 to 25 days.   

Amaranth seed or grain is also edible when toasted or milled into flour.  Native Americans used Amaranthus species as a food source for centuries. Today, flour and grain products are available on grocery shelves in the U.S. with recipes of all kinds on the internet. For those with celiac disease, milled amaranth is a gluten-free flour substitute.

Amaranthus seed oil is a source of squalene, which is a naturally-occurring compound used in cosmetics. It is used as an emollient, hydrating, and antioxidant agent in sunscreen, lotion, lipstick, eye makeup, etc. Plant-based squalene is used as an alternative to that extracted from the liver of sharks.

Although waterhemp, pigweed, and Palmer amaranth are problematic weed species of Amaranthus, the ornamental and edible types of amaranth are generally not considered invasive in gardens.