What Is Pigweed and How Do I Get Rid of It?

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Pigweed, also known as amaranth, has multiple personalities and can even be eaten! If you want to get rid of this weed, here's what to do.

No one is 100 percent sure, but pigweed may have gotten its name because it was used as food for pigs. In some places this weed, also known as amaranth, is an important source of nutrition for people as well.

If you spot this common weed growing in your garden or lawn, you probably just want to get rid of it. Here’s what you need to know.

What is Pigweed?

Pigweed is just that — a weed. Yet that doesn’t tell the entire story.

Yes, it’s a weed and that’s a legitimate four-letter word for lawn and garden enthusiasts. But did you know there are different types of pigweed? They’re all classified under the species Amaranthus, but that’s where the similarities end.

Amaranthus blitoides, AKA prostrate pigweed, is the one we’ll focus on here. It’s the one that shows up in your garden or hides in your lawn.

Prostrate pigweed — AKA mat amaranth, prostrate amaranth or spreading pigweed — is a summer annual that acts like a perennial. Although it completes its life cycle in one growing season, it can come back year after year, seemingly resisting any attempts to eradicate it.

That’s because, in any given year, it produces and disseminates more than 100,000 small black seeds that look like tiny grains of sand. These seeds can lay in the soil dormant for up to 20 years before randomly germinating into problematic weeds when conditions are just right.

What Does Prostrate Pigweed Look Like?

This lawn and garden adversary is a low-growing plant with alternate, pale-to-shiny dark-green leaves that are oblong to egg-shaped. These leaves can be to some extent pointed or rounded with a slightly indented leaf tip.

The light green to reddish plant stems hug the ground. Often they form thick, circular mats via one- to three-foot-long stems when allowed to mature. If you look closely, you may find small, greenish flowers in dense clusters at the leaf axil, where the leaf meets the plant stem.

Types of Pigweed

Prostrate pigweed is our focus here. However, there are other species worthy of mention.

Rough pigweed (Amaranthus retroflexus), also known as redroot pigweed, redroot amaranth, careless weed or wild beet, can be found throughout North America. Surprisingly, besides being an agricultural nuisance, it has a few delightful culinary attributes which we’ll touch on later.

Waterhemp and Palmer amaranth are classified as pigweeds but not considered a problem in home lawns and gardens. Reaching a towering height of three to eight feet, they are most often found in agricultural crops and along fence lines.

Why Do Lawns Get Pigweed?

All weeds are opportunistic. If there’s a “crack in the door,” they’ll enter. Lawns that lack turf density have exposed ground where weeds, like prostrate pigweed, can get a foothold.

Like most lawn weeds, the presence of pigweed indicates your lawn lacks something. You can improve lawn health by fertilizing and maintaining proper soil moisture.

Are There Benefits to Pigweed?

For those who enjoy foraging for natural foods, pigweed can offer some great opportunities. Almost every part of a pigweed plant is edible. Leaves can be eaten raw as part of a healthy salad, or cooked like spinach and eaten as a vegetable. Pigweed greens are rich in iron, calcium, niacin as well as vitamins A and C.

Pigweed seeds, with vitamins A and C plus calcium. can be eaten raw or cooked as a hot cereal. They can also be ground into flour for baking, and popped like popcorn for a snack.

Always wash collected plants thoroughly before consuming in case they were treated with chemicals.

How To Get Rid of Pigweed

Start with the old-fashioned way: Hand-pulling the weeds. This can be arduous, but it provides the best results and is environmentally-friendly (chemical-free). Smaller plants are easier to pull. Do it when the ground is soft and get as much of the root as you can. And if you compost, throw the pulled weeds into the bin.

Most conventional broadleaf herbicides like Bonide Weed Beater Ultra Lawn Weed Killer or Ortho Weed B Gon Weed Killer RTU will do an effective job. Of course, when using any pesticides, always follow the directions on the product label.

Because pigweed is an annual, it can be effectively controlled with a pre-emergent herbicide in the spring. The same one you use for crabgrass control can help prevent pigweed from sprouting in your lawn. Something like The Andersons Barricade Professional-Grade Granular Pre-Emergent Weed Control or Scotts Turf Builder Halts Crabgrass Preventer will kill small pigweed seedlings as they attempt to emerge in the spring.

Combination products of pre-emergent and post-emergent herbicides, like Gordon’s Trimec Crabgrass Plus Lawn Weed Killer or Ortho WeedClear, prevent new pigweed plants from germinating and control existing weeds in a single application.

You can also use nonselective herbicides containing glufosinate such as Primesource X-Out Non-Selective Herbicide. But remember, they will kill everything you spray, including your lawn. Be careful!

Joe Churchill
Joe Churchill is a Senior Turf Specialist for Reinders, Inc. in Plymouth, MN with a passion to promote realistic and environmentally-sound turfgrass maintenance practices through responsible use of water, fertilizers, pesticides and other inputs. Joe's client base includes professional turf managers serving the lawn care, sports turf and golf course industries. His lawn is the envy of the neighborhood and, in his free time, he enjoys kicking back on the Northshore of Lake Superior.