Amaranthus cruentus aka Red Amaranth

Amaranthus cruentus is an easy-to-grow annual that thrives with minimal care. It tolerates a wide range of soil types and pH levels, requires no pruning, and grows rapidly from seed. The main requirements are full sun and frost-free conditions, making it ideal for summer gardens in most climates.

This fast-growing annual reaches 1.5-2.5 meters (5-8 feet) in height with a spread of 0.1-0.5 meters (4-20 inches). It achieves full size within a single growing season, with stems becoming thick and branched. First leaf harvests are possible just 30-50 days after sowing, demonstrating its remarkably rapid growth rate.

This warm-season plant thrives in temperatures between 22-28°C (72-82°F) but tolerates a range from 10-45°C (50-113°F). It is frost-tender and will be killed by temperatures at or below 4°C (39°F). For best results, grow during warm summer months and protect from any cold snaps.

Amaranthus cruentus is not particularly demanding regarding humidity. It originates from tropical America and can handle both humid and drier conditions once established. The plant is listed as drought-resistant, indicating good tolerance for lower humidity environments, though it performs best with consistent soil moisture.

Amaranthus cruentus produces spectacular flowering plumes from July through September. The dense, feathery inflorescences appear in striking colors including deep red, purple, rust, orange, and cream, with spikes that can reach 50 centimeters long. The plant is monoecious with separate male and female flowers on the same plant, and seeds ripen from August to September.

Amaranthus cruentus is best grown outdoors as a summer annual in USDA zones 4-10. It requires a sheltered position in full sun with at least 6-8 hours of direct sunlight daily. In cooler climates, start seeds indoors in early spring and transplant after the last frost. The plant cannot survive temperatures below 4°C (39°F).

Mix tiny seeds with sand (1:100 ratio) for even distribution and sow at 1-2 cm depth. Seeds germinate rapidly in warm soil but poorly in cold conditions. Alternatively, stem cuttings from growing plants root readily.

The main pests are aphids, leaf-chewing insects, and spider mites. Common diseases include anthracnose (causing leaf lesions), damping-off in wet conditions, and wet rot. RHS notes susceptibility to plant viruses. Avoid overwatering to prevent root rot, and use integrated pest management rather than heavy chemical treatments.

Amaranthus cruentus is wind-pollinated and self-fertile, meaning a single plant can produce viable seeds without cross-pollination. The species is monoecious, bearing both male and female flowers on the same plant. This makes seed saving straightforward, though isolation from other amaranth varieties is recommended if maintaining pure strains.

Amaranthus cruentus is highly edible with a 5/5 edibility rating. Young leaves are cooked like spinach and are rich in vitamins A and C, iron, and calcium. The seeds are among the most nutritious pseudo-grains, containing complete protein with high lysine content. Seeds can be popped like popcorn, ground into flour, boiled into porridge, or sprouted for salads.

Amaranthus cruentus has a medicinal rating of 2/5, indicating modest traditional uses. These include diuretic properties, tapeworm expulsion, and topical applications of macerated plant water for limb pain. Root preparations boiled with honey have been used as infant laxatives, stem ash applied to wounds, and heated leaves applied externally to tumors.

Beyond food and medicine, Amaranthus cruentus provides natural dyes—yellow and green from the whole plant, and red from red-form inflorescences. The dried plant can be burned as a potash source. It also functions as a dynamic accumulator in food forests, drawing nutrients from deep in the soil. The dramatic flower plumes make excellent cut flowers and dried arrangements.

Several cultivated varieties exist, with 'Oeschberg' being notable for high grain yields (up to 2.5 tonnes per hectare). Ornamental varieties feature particularly bright-red inflorescences and are valued in cut flower arrangements. Some seed mixtures emphasize pale-colored forms. The species shows natural variation in flower color from deep red and purple to rust, orange, and cream.

Amaranthus cruentus originates from tropical America, specifically the region from Central Mexico to Nicaragua. The exact wild habitat is obscure as the species has been cultivated since ancient times and is no longer found in truly wild situations. It was a sacred crop to the Aztecs and has since naturalized as an agricultural plant worldwide in tropical to warm-temperate regions.

As an annual, Amaranthus cruentus has a straightforward seasonal cycle. Start seeds indoors in early spring, transplant outdoors after last frost when soil warms. Through summer, water freely to prolong flowering and harvest leaves regularly. In late summer/autumn, allow flower heads to mature for seed harvest. The plant dies with first frost—collect seeds for next year's sowing.

Red Amaranth should be watered regularly, allowing the soil to dry out between waterings.

Red Amaranth loves a well-draining soil. Perlite and vermiculite help with drainage, while coco coir adds organic matter, so a good potting soil mix will have all three. You can improve store-bought soil by adding some perlite to it.

Red Amaranth requires abundant, bright and direct light. Placing it less than one foot from a window is the best way to make sure the plant receives enough light to survive and thrive. Depending on your region, however, the current weather can affect the placement of the plant in your home. For example, in some areas the sun may be too direct and intense, so it's best to place it farther away from the window. You may also need to adjust your placement according to the season as the sunlight can change intensity over the course of the year. If you live in a region with significant temperature fluctuations, such as a desert, you may need to place the plant a bit farther away from the window to avoid extreme heat or cold. With some care and attention, your Mexican Grain Amaranth will be sure to bring you many years of beauty and enjoyment.

The Red Amaranth should be repotted either when it doubles in size or annually, whichever comes first. Providing new potting soil with all the vital nutrients annually is enough to support the growth of the plant, and thus, there is no need for fertilizer. Remember that plants derive their energy from the sun, not fertilizer.

Ploi's records do not contain confirmed information on the toxicity of this particular plant. In the event of accidental ingestion of plant material with questionable toxicity by you, a family member, or a pet, it is always a good idea to consult a healthcare professional.