Weeds: Redroot Pigweed

Redroot Pigweed (Aramanthus retroflexus) is one of four commonly found pigweeds in the United States, though it comes to us from the tropical Americas. Its many common names include red-root amaranth, red-rooted pigweed, common amaranth, pigweed amaranth, common tumbleweed, rough pigweed, and careless weed. The plant can grow up to 7 feet tall, but typically gets to be 1 to 3 feet tall, and can be identified by its reddish taproot and short rough stem and leaf hairs.

The plant is useful as a companion plant to trap a variety of pests including leaf miners. Despite this possible benefit, it is considered an alternate host for green peach aphids, tarnished plant bugs, European corn borers and flea beetles. It also hosts the cucumber mosaic virus, and various other viruses which attack sugar beets.

It is an annual and needs light to grow. Redroot pigweed not only needs light, but also high temperatures to germinate – preferring the 70-85 degree Fahrenheit range. It will easily acclimate to any soil and any temperature. Considered highly invasive, pigweed is now resistant to many types of herbicides. It grows up to an inch a day, so it thrives in climates with drought problems. Ungerminated seeds can live for up to 40 years and still germinate.

Redroot pigweed is edible – the leaves can be eaten raw or cooked. The seeds however, are more commonly used since each plant produces thousands of seeds (estimated 100,000 to 500,000 per plant). They are very nutritious, and are easily harvested despite their small size. It was eaten by the Apache, Chiricahua, Mescalero, Isleta, Jemez, Laguna, Mohegan, Navajo, Mendocino, Pueblo, Tewa, Keres, Acoma Cochiti and Iroquois either seeds, leaves or both.

However, it can cause allergic reactions to some people and it is reported to cause nitrate poisioning in livestock who eat it (likely due to its ability to bio-accumulate nitrates). It may have some usefulness medicinally as well. In North America, it was used by native populations for a variety of medicinal purposes. The Acoma and Laguna used it for stomach problems, the Cherokee to help reduce bleeding from menstruation, the Delaware used it for hoarseness.

What does it mean?

You may have low calcium and high potassium, as well as high insoluble phosphates. Your soil might be low on surface organic matter but have a solid decay system. McCaman says to correct by adding phosphorus accumulators to the garden and by pulling and mulching the weed before seeds set to retain nutrients in the garden. Pfeiffer suggests adding lime to the soil, and regularly till or harrow it to break up hard ground.

Want to learn more?

If you would like to learn more about weeds, why they grow, and what that means about your garden, consider the following texts:

Weeds and Why they Grow, by Jay L. McCaman

Weeds and What They Tell Us, by Ehrenfried E. Pfeiffer

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