Weeds as Indicator Plants

What Common Weeds Can Tell You About Your Soil

March 21, 2019

Rate this Post: 

Average: 4.3 (179 votes)

Get a Free Garden Planner Trial!

Try out our Garden Planner with a free 7-day trial—ample time to plan your dream garden!

Try the Garden Planner

Frost Dates

Enter a Location

Weeds are annoying, but they can also be great indicator plants, telling you what nutrients your garden is lacking or what it has in excess. Before you pull out the pesky weeds that are overtaking your cultivated plants, take a minute to notice what is growing.

That’s right—read your weeds! They are excellent indicators of soil conditions and quality. If you have large patches of one kind of weed, your garden is trying to tell you something.

Note: A weed is simply a plant that’s located in an undesirable place. Some “weeds” are in fact great edible or ornamental plants for the garden!

Common Weeds and What They Indicate

  • Amaranth (also called red root pigweed) grows in rich soil, high in nitrogen.
  • Bindweed grows in crusty or compacted soil.

Common chicory can be an indicator of rich soil.

  • Chickweed and chicory like rich soil—high in nitrogen—and will grow well in sweet, compacted soil.

If you have groundsel, you have good soil.

  • Common groundsel is an indicator of rich soil.
  • Crabgrass grows where the soil has been depleted of nutrients and is low in calcium.
  • Dandelions indicate poor soil that is low in calcium, but high in potassium. Luckily, they can also make a yummy snack! Check out our dandelion recipes.

Bitter dock might grow if you’ve planted near a swampy area.

  • Dock and goldenrod grow in wet, poorly drained soil.
  • Fragile fern grows in near-neutral, dry conditions. Ferns also might be able to tell you something based on their history of folklore.
  • Henbit indicates high nitrogen.

Knapweed looks like its cousin the bachelor’s button.

  • Knapweed indicates rich soil, high in potassium.
  • Knotweed grows where the ground is compacted.
  • Lamb’s quarters indicate rich soil, high in nitrogen.
  • Little blue-stem (also called poverty grass) grows in dry, sandy, run-down soil depleted of nutrients.

There are many kinds of mosses that thrive in moist shady locations.

  • Moss indicates soggy, acidic soil that is low in nutrients.

Common mullein indicates that you might need to make your soil more alkaline.

  • Mullein grows in acidic soil with low fertility.

Mustard is commonly found in pastures & fields.

  • Mustard grows in dry, sandy soil, high in phosphorus.

Ostrich fern grows in rich soil.

  • Ostrich fern indicates an exceptionally fertile location.

Common wood sorrel (which you might mistake for clover) shows that your soil might need a calcium treatment.

  • Oxalis, or wood sorrel, indicates low calcium and high magnesium.

Ox-eye daisy is found in areas of low fertility.

  • Ox-eye daisies grow in acidic, often soggy soil with poor fertility.
  • Pearly everlasting grows in acid soil that is low in nutrients.
  • Peppergrass indicates sweet soil.

Plantain is a stubborn weed that often grows in heavy clay.

  • Plantain grows in compacted, sour soil with low fertility and often indicates heavy clay. Like prostrate knotweed, it has evolved to survive being trampled and can grow in heavily trafficked garden paths.
  • Purslane prefers rich soil and is an indicator of high phosphorus. Like dandelions, purslane is edible and offers health benefits. Make the most of your common weed education and explore some purslane recipes.
  • Quack grass will grow in heavy clay or compacted soil.

Queen Anne’s lace indicates poor dry soil.

  • Queen Anne’s lace grows where the soil is poor, but on the sweet side.
  • Ragweed indicates low fertility.
  • Sensitive fern grows in poorly drained soil that is low in nutrients.
  • Sweet fern prefers sandy, acidic soil.

Stinging nettle doesn’t just indicate rich soil; it also has some valuable qualities.

Sheep sorrel grows in acidic soil that is low in nitrogen.

  • Sheep sorrel indicates dry, sandy, sour soil depleted of nutrients and low in calcium.

Yarrow is found on poor, dry, sandy soil where little else will grow.

  • Yarrow grows where potassium and fertility are low and the soil is sandy and dry.

Using This Information

The weeds listed above provide important clues about your soil’s fertility. Use this information to your advantage when amending your soil or deciding what to plant where.

If you have a hard time identifying your garden weeds, look at this list of common weeds.

After discovering what they mean, find out how to get rid of your weeds, if you so desire.

Dandelions and purslane are not the only edible weeds! Find out which of these weeds you can eat.

About This Blog

Get inspired by Robin Sweetser’s backyard gardening tips and tricks. Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. She and her partner Tom have a small greenhouse business and also sell plants, cut flowers, and vegetables at their local Farmer’s Market.

2019 Garden Guide

Reader Comments

Leave a Comment

Bother some grass.

I have a grass that is brighter then regular, is very short. It seems to grow around the corners of concrete. Any body know what it is & how to get rid of it?

Without seeing a picture it

Without seeing a picture it is hard to identify since there are so many types of grasses. Pulling it out by the roots will eliminate the problem. Be sure to do it before the grass sets seeds or you will be fighting it forever. You can also try to smother it with a solid mulch such as black plastic, newspaper, or cardboard.

I wonder

I wonder how many of these aren't weeds at all but ended up being classified that way because someone in the early 20th century or in the 19th century decided they didn't want them around so they convinced everyone they were weeds.

"Indian paintbrush"

Could anyone tell me what having small patches of 'indian paintbrush' would indicate about my soil?

Thistles and crab grass

I have a bumper crop of both each year, I spend hours digging to china to try and get all the root. Its a losing battle. We have a clay soil that I have been adding compose to for years. I don't use chemicals on my garden as we have digestive issues and don't want to compound these issues. Any suggestions on how to get rid of these weeds would be greatly appreciated.

Thank you

Weeds are looked at because of their inconvenience therefore the focus is limited to control measures. We hardly see weeds as an opportunity to detect impending soil deficiencies that can be use as indicator key to improve request for soil testing.

One man's weed is another man's Herb;

One mans weed is another man's Herb; as the poster wrote; Weeds can be food; the Herb I like is Mullein; this is the tall Herb with the "yellow spiked flower"; the American Indians would use the Leaves to line their Moccasins in the winter; the flowers are used for Tea; I have made Plantain greens; a bit like spinach; Queen Anne's Lace is the Wild Carrot; etc.";

Strange weed

I have a weed growing that has a circumference of 6" right now and is 12 feet tall and is still growing, large saw tooth leaves extending up to 18" out from the stalk. It showed up two years ago. Dies off in the late fall. Gotten taller from first to second year. Has a smaller one growing beside it. Nobody knows what it is. Do you know? Saw picture of it on internet but could not get any info. Father had dairy farm for 50 years and never saw anything like it.

Strange Weed

If it has a flower, start googling with the flower color, such as yellow flower, very tall, perennial. I have identified several previously unknown to me using this formula.

Strange weed

It sounds like the giant hogweed which can be very dangerous to handle. The sap can give you terrible blisters and even cause blindness. I would call your DEC and report it.


How do I get rid of an invasion of chickweed in my garden. There are spots that are like a large carpet of chickweed, and chokes out the vegetables. Please help.

Chickweed can be hard to

Chickweed can be hard to totally eradicate. It is imperative to rip it out before it sets seeds. Since it is shallowly rooted it is easy to pull out but tends to snap off and leave bits of root behind that will just regrow. It may take several years of diligence to pull it all out and dig up the remaining roots but don’t give up!

Sandy soil conditions.

I notice each time Sandy soil is mentioned following it is "nutrient depleted". I somewhat object to this indictment. It's just sandy soil and you often find it along or within miles of ocean and lake shorelines. It only means that you will need to amend the sandy soil in different ways dependent on what you wish to grow and some landscaping choices might never do particularly well. I've lived in places with great differences in conditions. I grew up in an area with sandy soil and find myself living in a residence with those conditions once again. We are starting with a blank landscape here but I can assure you that within 2 years it will be a lush paradise of greenery and productive gardens. I agree that "weeds" can be indicators but what people often call "weeds" are sources of food and medicines that have overgrown or are growing where we don't want them. In my humble opinion grass is a weed unless it's the ornamental variety. Haha

As you have stated, sandy

As you have stated, sandy soil can be improved easily by the addition of organic matter to increase its ability to hold moisture. Then the nutrients won’t leach out as fast.



Can i republish this article i Swedish?

I found this article very helpful and would like to translate it and post it on my blog in Swedish with its images. Can I?

Thank you for your kind words

Thank you for your kind words, but duplicating the entirety of our writers’ works (even in another language) is against our terms of use. See the bottom of our site for Terms of Use and contact us for special exceptions.

creeping charlie

How do I stop the spread and get rid of?


how do I get rid of it--it's coming under my neighbor's fence (he does not tend his yard at all ) and that and his dandelion are invading my grass. great article--but would hope there's some indication that Knap weed is considered a noxious weed here and needs to be removed.

Creeping Charlie is a tough

Creeping Charlie is a tough one to eradicate. It is the mint family and will form new roots all along its stem. It is shallow-rooted and can be ripped out with an iron rake or pulled by hand if you don’t have too much. It thrives in shady moist conditions so changing those conditions by thinning trees or removing shrubs to get more light into the area is an extreme measure but may do the trick as would improving drainage in that area. You could try smothering the  plants with layers of newspaper covered by mulch or compost or black plastic.

Contradictory weed

My soil is not clay, but I do have plantain. I also have oxalis, wood sorrel, dandelions, creeping charlie and a bunch I can't identify. It does seem the dandelion season is over.

Plantain will grow anywhere

Plantain will grow anywhere with heavy or compacted soil. It grows in the driveway to our greenhouse and in most of my garden paths where it gets trampled daily.


I have a weed that has small purple flower and thorns what is it? how do i get rid of it?

Hard to tell without seeing a

Hard to tell without seeing a picture of it.

purple flower with thorns

Good chance it may be "horse nettle" seed pods are round balls that are green and turn yellow when mature.

Maybe Cranesbill? Looks

Maybe Cranesbill? Looks similar to hen it but for the height of the plant and the horns.


BONUS: You’ll also receive our Almanac Companion newsletter!

The Almanac Webcam

Chosen for You from The Old Farmer's Store