When they grow where we don’t want them, weeds can be a pain! But did you know that 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—you can 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, so before you toss them on the compost pile consider their other uses.
Common Weeds and What They Say About Soil
Amaranth (Amaranthus spp.) grows in rich soil, high in nitrogen.
Bindweed (Convolvulus arvensis) grows in crusty or compacted soil.
Common chicory can be an indicator of rich soil.
Chickweed (Stellaria media or Cerastium spp.) and chicory (Chicorium sp.) like rich soil—high in nitrogen—and will grow well in alkaline, compacted soil.
Common groundsel (Senecio vulgaris) is an indicator of rich soil.
Common groundsel. Remember: “If you have groundsel, you have good soil!”
Crabgrass (Digitaria spp.) grows where the soil has been depleted of nutrients and is low in calcium.
Dandelions (Taraxacum officinale) indicate poor soil that is low in calcium, but high in potassium. Luckily, they are great for springtime pollinators and can also make a yummy snack! Check out our dandelion recipes.
Dock might grow if you’ve planted near a swampy area.
Dock (Rumex spp.) and goldenrod (Solidago spp.) grow in wet, poorly drained soil.
Fragile fern (Cystopteris fragilis) grows in near-neutral, dry conditions. Ferns also might be able to tell you something based on their history of folklore.
Henbit (Lamium amplexicaule) indicates high nitrogen.
Knapweed looks like its cousin, bachelor’s button.
Knapweed (Centaurea spp.) indicates rich soil, high in potassium.
Knotweed (Polygonum spp.) grows where the ground is compacted.
Lambsquarters (Chenopodium album) indicates rich soil, high in nitrogen.
Little blue-stem (Schizachyrium scoparium) grows in dry, sandy, run-down soil depleted of nutrients.
There are many kinds of mosses that thrive in moist, shady locations.
Moss of most kinds indicate soggy, acidic soil that is low in nutrients.
Common mullein indicates that you might need to make your soil more alkaline.
Mullein (Verbascum thapsus) grows in acidic soil with low fertility.
Mustard is commonly found in pastures & fields.
Mustard (Brassica spp.) grows in dry, sandy soil, high in phosphorus.
Ostrich fern grows in rich soil.
Ostrich fern (Matteuccia struthiopteris) 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 (Leucanthemum vulgare) grow in acidic, often soggy soil with poor fertility.
Pearly everlasting (Anaphalis margaritacea) grows in acid soil that is low in nutrients.
Peppergrass (Lepidium verginicum) indicates sweet soil.
Plantain is a stubborn weed that often grows in heavy clay.
Plantain (Plantago spp.) 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 (Portulaca oleracea) 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.
Quackgrass (Elymus repens) will grow in heavy clay or compacted soil.
Queen Anne’s lace indicates poor dry soil.
Queen Anne’s lace (Daucus carota) grows where the soil is poor, but on the sweet side.
Ragweed (Ambrosia spp.) indicates low fertility.
Sensitive fern (Onoclea sensibilis) grows in poorly drained soil that is low in nutrients.
Sweet fern (Comptonia peregrina) 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 (Rumex acetosella) indicates dry, sandy, acidic soil depleted of nutrients and low in calcium.
Yarrow is found on poor, dry, sandy soil where little else will grow.
Yarrow (Achillea millefolium) 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.