Common Amaranth (Amaranthus Retroflexus) Growing & Care Guide for Gardeners

Article by Dean Ravenscroft, Ph.D. - Updated 31st Jan 2024

Better known as Pigweed, the Common Amaranth (Amaranthus Retroflexus) reaches an height of about 3 feet (0.9 m). Other common names for this plant include Redroot Amaranth or Wild Beet

Although many people consider it to be a weed, this is perhaps one of the best Amaranths to grow if you wish to harvest the seeds for grain.

In fact, Indian chefs from Kerala often make Thoran, one of their signature dishes, with this hardy little plant.

Pigweed, somewhat notoriously, also forms tumbleweeds in the wild.

If you're interested in growing a garden of these beautiful grain amaranths yourself, there are a few things worth noting before you start.

The leaves of Amaranthus retroflexus also have culinary use, and are often used as a replacement for spinach plants in Mexico – where it is native to.

Amaranthus retroflexus photograph by Matt Lavin.

This annual Amaranth grows well in USDA zones 3 to 11, and is rated at UK hardiness H4. This makes it hardy down to about -10°C (14°F). The plant is sensitive to very long cold conditions, so shouldn't be grown in extreme climes.

Primarily, these Amaranths are summer annuals and start to bloom in July. Blooming occurs from the middle of summer through to early autumn. The flowers are inconspicuous and green in color. They form dense panicles, which can reach up to eight inches (20 cm) in length.

Plants carry either male or female flowers (monoecious), and are wind pollinated.

Seeds (1/10th inch / 2 mm) begin to ripen in the late summer and early fall, starting around August and continuing to October.

Once blooming has finished seeds will set and ripen from late summer through to the middle of autumn (Seeds (1/10th inch / 2 mm).

Gardener's HQ Guide to Growing Common Amaranth

Pigweed is an outdoor plant that can't grow without plenty of sunlight, so make sure it is located in a sunny area, well outside the reach of any heavy shade (some light shade is usually fine).

They're suitable for a wide range of soil types and can endure a lack of water, but do best when they have a steady supply. Plants prefer a moist soil, as this promotes growth. Water regularly

Common Amaranth Seeds can be sown in their final location towards the end of spring.

Or start Amaranthus Retroflexus in the greenhouse and transplant out following the last frost of spring

Does not like wind, so grow in a sheltered location.

Can be grown in pretty much any soil types and acidities. For best results grow in a rich soil.

Be sure to dig your trenches deep to give plant roots plenty of room to clump and grow.

If you're at all intending to consume this plant in any way, whether medicinal or food, you should not use inorganic fertilizers as nitrates have a tendency to congregate in the leaves.

The reasoning for not feeding Amaranthus Retroflexus inorganic fertilizers is that the plants have very effective photosynthesis (C4 pathway). This can lead to an abundance of unwanted chemicals being available to the leaves and seed. This can result in the plant becoming toxic to humans.

Amaranthus retroflexus makes a good companion plant for many types of vegetables. Some of the ones recommended by the gardenersHQ website include Eggplants, Tomatoes, Peppers and Maize.

I hope that you enjoyed this guide on how to grow Amaranthus retroflexus. You may also enjoy the following Amaranthaceae growing guides: How to grow Kochia and Gomphrena plants.