Pigweed. A farmer’s natural enemy.
This weed is part of this amaranth genus. It’s very similar to amaranth but, depending on the species, can be vastly different from the ancient grain. These weeds tend to plague cotton and soy fields.
For this article’s purpose, we are focusing on amaranthus retroflexus and amaranthus palmeri, which typically are known as weedy amaranth and not edible grain.
Is the pigweed harmful? How destructive is it? Can I easily get rid of it? Keep reading to answer all your questions about this strangely named weed.
How to Identify Pigweed
How did it get its name? Because these weeds grew abundantly on farmland, the flowers and seeds were added to the fodder or feed for pigs.
But what does it look like?
Pigweed or amaranthus retroflexus has pointed dark green leaves with rounded tips between smooth notches. Leaves are 1 to 6 inches long and ½ to 3 inches wide. Each leaf is arranged oppositely along a 3 to 6-foot tall stem.
This weed grows green flower clusters that are thin and cone-like and contains more than 100,000 seeds. These flower clusters branch off individual stems and grow to about 2 inches long.
You’ll likely see pigweed growing in croplands or farm fields throughout the US and Southern Canada. The weed is known to thrive in high heat and dry drought-like conditions.
Why is Pigweed Considered a Weed?
Pigweed is an annual flowering weed, but what exactly defines a weed? A weed is any plant that competes with other cultivated plants, such as crops. This weed grows throughout crops like cotton, corn, and soy.
Pigweed has also established a reputation for tolerating almost all weed killers and herbicides. It’s especially hard to eliminate because they tend to hybridize themselves with all other weedy amaranth species to adapt and thrive in ever harsher conditions.
What Issues Are Caused by Pigweed?
This weed is abundant in field crops. It can contribute to crop loss in the worst cases, making this weed a farmer’s worst nightmare.
Pigweed competes with vegetables or plants it’s growing with, trying to rob them of light and water. If the crops next to the weeds grow taller, it rapidly increases its stem and leaf growth to ensure it gets to the sunlight first.
This kills the crops because they cannot keep up with the weed’s rapid growth. Not all crops will be killed by pigweed, but this plant can cause major problems.
How Does Pigweed Spread?
If having over 100,000 seeds per plant wasn’t bad enough, these seeds are spread by wind, water, animals, and even farm machinery. Any slight disturbance to the plant causes seed loss.
What is most impressive is once a seed has fallen into the soil, it can stay dormant for up to 20 years, depending on how deeply it’s buried. It’s safe to say that once a field has pigweed, it most likely always will.
Pigweed seeds must only be buried in about ½ inch of topsoil to germinate. This is why they can grow so rapidly. A small storm blows through, knocking the seeds to the ground and covering them in some soil, adding a bit of rain to the mix, and these rapidly growing weeds show up almost overnight.
This weed may also be spread through many commercial birdseed mixes. It’s nothing new that most wild bird seeds contain some weed seeds, but knowing how invasive and troublesome this weed is, it’s surprising they let it slip through.
The seed is the size of a pinhead, so it is extremely difficult to sift out. If you enjoy providing food for your feathered visitors, do some research to learn how to avoid seed mixes containing noxious weeds like pigweed.
Or consider skipping birdseed altogether instead of adding plants that feed birds to your landscape or garden.
How to Get Rid of Pigweed
Unfortunately, pigweed is notorious for being a difficult weed to eradicate. Most species don’t respond to herbicides whatsoever.
Meanwhile, crop fields seem to be more influenced by practicing weed management and crop rotation. Tilling the ground may be worse when it comes to this weed. Tilling can bring up some of the dormant seeds from years prior.
Your best bet is trying to manage the weed versus killing it. Planting crops like velvet bean, cowpeas, and sun hemp creates a dense canopy suppressing growth.
In short, crop rotations and carefully planning the timing and severity of soil-disturbing field work are the most effective for controlling the weed. Pigweed most likely won’t react to commercial herbicides, so it’s best to try these non-chemical methods.
A Brief History
Pigweed is native to North and Central America but has spread worldwide. Human commerce and crop cultivation most likely led to this pesky weed traveling to Europe, Asia, and Australia.
Can Pigweed be Used for Anything Beneficial?
Unfortunately, pigweed is not used for much. It’s more of a nuisance than anything else and even most insects that cause plant damage won’t touch this weed.
The fruit and seed of the pigweed is the only edible part of the entire plant. Mostly it would be ground into a powder that could be used in substitution for a cereal that can be eaten raw or cooked.
The weed’s leaves, stems, and root systems are highly toxic to humans and animals. So it shouldn’t be in areas where horses, cattle, goats, or sheep graze. The good thing is most animals know not to mess with this plant and will steer clear of it.
The only positive aspect of pigweed is that it does attract pollinator insects. That can benefit crops – just don’t let this weed get too close to those crops!
Wrapping up Pigweed
This funny-named weed causes a ton of headaches to farmers worldwide. Commercial herbicides don’t affect this weed, and even animals and insects won’t have anything to do with it.
There are different ways to remove pigweed, and it may take some experimentation to find the best method. Still, there are many resources available regarding crop rotation and tilling times.
If you feel like you need to learn more about these pesky garden tenants, check out our weeds page to learn all about different weed varieties, treatment options, and surprising information.
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Lauren has three main passions: her family, writing, and gardening! Lauren has spent countless hours in her garden tending to different plants, whether those be beautiful flowers, vegetables, or different perennials.
Rest assured that if it concerns plants and gardens, Lauren has got you covered. So, when needing advice or looking for the best new gardening gadget, you have come to the right place and the right author.