19 August 2021

Here come the "superweeds"

Excerpts from an interesting longread at The New York Times:
If there’s a plant perfectly suited to outcompete the farmers, researchers and chemical companies that collectively define industrial American agriculture, it’s Palmer amaranth. This pigweed (a catchall term that includes some plants in the amaranth family) can re-root itself after being yanked from the ground. It can grow three inches a day. And it has evolved resistance to many of the most common weed killers...

The plant in his hands was a Palmer amaranth descendant that had demonstrated resistance to 2,4-D, one of two active ingredients in compounds used to defoliate forests during the Vietnam War...

Superweeds — that is, weeds that have evolved characteristics that make them more difficult to control as a result of repeatedly using the same management tactic — are rapidly overtaking American commodity farms, and Palmer amaranth is their king. Scientists have identified a population of Palmer amaranth that can tolerate being sprayed with six different herbicides (though not all at once), and they continue to discover new resistances. By now, it’s clear that weeds are evolving faster than companies are developing new weed killers...

It’s hard to estimate exactly how much damage has already been wrought by herbicide resistance; the weeds are gaining ground faster than scientists can survey them...

Palmer amaranth benefits from incredible genetic diversity. It mates sexually (obligate outcrossing, in biology-speak), and female plants produce hundreds of thousands of seeds each year. The plants that sprouted with random mutations that inadvertently equipped them to survive showers of herbicide lived to reproduce with one another. Then, once applications of Roundup annihilated all the weeds in a field except the resistant Palmer amaranth, the pigweed could spread without competition...

Ultimately, Roundup was no match for the pigweed’s evolutionary vitality. Roundup-resistant Palmer amaranth populations quickly spread through the South, then moved north, hidden at times in cottonseed hulls used for animal feed. Once consumed, the tiny seeds passed intact through the digestive systems of the cows that ate them. Farmers who sprayed the contaminated cow manure on their fields — a common practice, as a cheap form of fertilizer — unwittingly assisted the weed’s spread. Palmer amaranth, the ultimate opportunist, now grows in at least 39 states.
More at the link.


  1. I wonder if it is remotely feasible that such a plant could be used for food or some commercially viable enterprise? I know that kudzu did quite a bit of damage in the South, choking out trees and the such.

    It might be that it could be useful as bio-fuel--especially with it growing so fast.
    If nothing else, it MAY be that Palmer amaranth might serve as a ground cover to slow erosion...or perhaps to "tame" deserts.

    For that matter, it may be that it could be "harvested" and used for wood-burning stoves or furnaces.

    1. Perhaps just grow immense quantities of the pigweed, let it soak up all the CO2 from the air to build plant fiber, then dig a big hole and bury the plants to sequester the carbon. Making coal, instead of burning it

  2. https://www.nationalgeographic.com/culture/article/130812-amaranth-oaxaca-mexico-obesity-puente-food

  3. From Wikipedia: (https://en.wikipedia.org/wiki/Amaranthus_palmeri)

    The leaves, stems and seeds of Palmer amaranth, like those of other amaranths, are edible and highly nutritious. Palmer amaranth was once widely cultivated and eaten by Native Americans across North America, both for its abundant seeds and as a cooked or dried green vegetable. Other related Amaranthus species have been grown as crops for their greens and seeds for thousands of years in Mexico, South America, the Caribbean, Africa, India, and China.

    This from an article on eattheweeds, 2011: (http://www.eattheweeds.com/palmer-amaranth/)

    Amaranth, in general, is a good wild food. It occupies the middle ground between excellent and poor. When collected very young Amaranth is a dietary analogue to spinach, which is a relative. At the meristem stage, still young and tender because the cells are still growing, it’s a tasty green usually boiled. Later it becomes a source of grain. These stages, however, are dynamic, changing and they change at different rates with different species of amaranth. Some amaranths stay more palatable longer than others. More so, depending upon growing conditions, amaranth can also accumulate high levels of nitrates and oxalates making them less than desirable to eat, for you or livestock.

  4. On the subject of Weeds Gone Wild: https://www.youtube.com/watch?v=u5NxuEoXHn8 is a brilliant vid about the problems with Giant Hogweed in Russia


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