Weeds that Indicate Soil Conditions


Four Season Garden: How Weeds Can Help Identify and Correct Soil Problems

      
by BC Farms & Food  -  Permalink
May 16, 2017

Recognize these weeds? Weeds can tell you a lot about the condition of your soil. Not only that, weeds, when composted, help improve the soil by releasing into it the very minerals and elements it needs.
(Article and Weed Guide to Soil Conditions continue below slideshow.)

Cat’s Ear, also called False Dandelion, has tall yellow flowers similar to dandelion, and rounded, hairy leaves (unlike dandelion). Cat’s Ear typically indicates dry, free draining soil, but will also grow in moist areas.
Dandelion typically indicates heavy, compacted, acidic soil, but also grows in fertile well-drained areas. Dandelion's long taproots bring up calcium and other minerals from the subsoil. These can enrich the garden as dandelion decomposes.
Daisy (Bellis perennis) indicates dry, well-drained soil with low fertility. This low-growing plant with lobed leaves and small flowers is commonly found in lawns with worn-out neutral or acidic soils.
Plantain indicates acidic, compacted, low-fertility soil. Rich in calcium and magnesium, this wild plant also accumulates silicon, sulphur, manganese and iron. Decomposing plantain helps to alkalize the soil.
Buttercup indicates acidic, poorly-drained soil. Buttercup produces a toxin called protanemonin that may suppress growth of adjacent plants. Creeping buttercup draws potassium from the soil.
Horsetail indicates light, sandy, slightly acidic soil, and grows in moist conditions. Horsetail accumulates silicon, calcium, magnesium, and iron, which it releases back into the soil as it decomposes.
Chickweed grows in neutral, moist, sometimes heavy soils. Healthy chickweed indicates cultivated, fertile soil. Chickweed accumulates potassium and phosphorus which enhances the soil when it decomposes.
Purple Deadnettle, a member of the mint family, often indicates neutral, nutrient-rich soil. Deadnettle can grow in heavy clay areas, but prefers loamy soil. Purple Deadnettle is a valuable attractor of pollinators in early spring.
Sheep Sorrel indicates acidic, low fertility soil. Sheep sorrel accumulates calcium and phosphorus, minerals that de-acidify the garden. Composting sorrel helps to alkalize the soil.
Thistle indicates compacted, heavy, acidic soil. Its roots penetrate deeply and  help break up the subsoil. Thistle’s roots bring up iron and moisture for use by shallow-rooted plants. Thistle is often indicative of dry areas.
Bindweed indicates poorly drained, compacted, often crusty soil. Bindweed has a deep and extensive root system which stores nutrients for regrowth. Although it can grow in a range of conditions, bindweed prefers heavy clay soil.
Hairy Bittercress, a member of the mustard family with tiny white flowers, indicates poorly-drained, moist soil. Hairy Bittercress commonly grows in disturbed areas and is most prolific in early spring.
Dock indicates heavy, poorly-drained, waterlogged soils with increasing acidity. Dock has deep taproots that break up the subsoil. Dock draws up calcium, potassium, phosphorus and iron which is released into the soil when composted.
Quack Grass indicates heavy clay or crusty soil with poor drainage. Quack Grass has a net-like root system that helps control erosion on steep banks. Quack Grass accumulates potassium, silicon and other minerals.
Clover typically indicates moist, poor-fertility soil, that is low in nitrogen. It also indicates soil that is rich in potassium. Clover draws nitrogen from the air and fixes it into the soil when tilled under.
Vetch indicates poor fertility soil, low in nitrogen. A member of the pea family, vetch obtains nitrogen from the air and fixes it into the soil when tilled under. Vetch accumulates phosphorus, potassium, and other minerals, which can enrich the soil when composted.
 
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Cat’s Ear, also called False Dandelion, has tall yellow flowers similar to dandelion, and rounded, hairy leaves (unlike dandelion). Cat’s Ear typically indicates dry, free draining soil, but will also grow in moist areas.

What Weeds Can Do for the Soil

Weeds are pioneers. They are opportunistic plants that take root on disturbed or bare ground where the soil is too poor to support other kinds of growth. They thrive in these areas because they are adapted, with deep taproots or root nodules, to bring up or fix from the air the exact minerals and nutrients in which the soil is deficient.

A plot filled with weeds that can indicate soil conditions.

Dandelions, Purple Deadnettle, Clover, and Small-flowered Cranesbill take root in areas like this once bare piece of land.

In addition to concentrating elements and minerals into their structures, many weeds have extensive root systems which, as they decay, leave channels for drainage, and help build rich organic matter. Some weeds can also absorb excess salt from the soil.

To take advantage of the nutrients weeds accumulate as they grow, pull them when they reach their full growth, but before they go to seed. Let them wilt for a few days, then turn them under the soil or add them to your compost pile. As they decompose, their accumulated minerals will enrich your garden.

Weed Guide: Weeds as Indicators of Soil Conditions

Look at the weeds in your garden and use the guide below to determine what kind of soil you have. Note that some weeds, such as dandelions, take root under a variety of conditions. In this case, look to see what else is growing nearby and use the weed guide to draw conclusions.

Weeds that Grow in Acidic (Sour) Soil – low pH

Common plantain is a weed that can indicate soil conditions.

Common Plantain

Buttercup
Daisy
Dandelion
Horsetail
Knotweed
Moss
Mullein
Plantain
Sheep Sorrel
Stinging Nettle

 

Weeds that Grow in Neutral Soil

Chickweed
Daisy
Purple Deadnettle


 

Weeds that Grow in Alkaline (Sweet) Soil – high pH

Queen Anne's Lace is a weed that can indicate the condition of the soil.

Queen Anne’s Lace (Wild Carrot)

Chicory
Queen Anne’s Lace (Wild Carrot)
Salad Burnet

 

Weeds that Grow in Dry Soil

Cat’s Ear
Mullein
Mustard
Nettle
Pigweed
Sheep Sorrel
Speedwell
Thistle
Yarrow


 

Weeds that Grow in Hard, Crusty, Compacted Soil

Hedge Bindweed or Morning Glory is a weed that can indicate soil conditions.

Hedge Bindweed (Morning Glory)

Bindweed (Morning Glory)
Chickweed
Dandelion
Dock
Knotweed
Field Mustard
Nettle
Plantain
Quack Grass
Thistle

 

Weeds that Grow in Wet, Moist, Poorly-Drained Soil

Daisy (Bellis perennis) is a weed that can indicate soil conditions.

Daisy

Bindweed (Morning Glory)
Buttercup
Chickweed
Clover
Dock
Hairy Bittercress
Horsetail
Knotweed
Joe-Pye Weed
Moss
Quack Grass

 

Weeds that Grow in Low Fertility Soil

Vetch is a weed that can indicate soil conditions.

Vetch

Clover
Crab Grass
Daisy
Dandelion
Mugwort
Mullein
Plantain
Ragweed
Sheep Sorrel
Queen Anne’s Lace (Wild Carrot)
Thistle
Vetch
Yarrow

 

Weeds that Grow in Fertile Soil

Purple Deadnettle is a weed that can indicate soil conditions.

Purple Deadnettle

Chickweed
Chicory
Clover
Dandelion
Lamb’s Quarters
Mugwort
Pigweed
Purple Deadnettle
Purslane
Stinging Nettle

 

 
More Four Season Garden articles:
 
A rock wall creates a microclimate that protects zucchini plants.Creating Microclimates to Protect Plants


Bright blue cornflowers or Bachelor's Buttons help bees through the winter.10 Plants that Help Bees Through the Winter

6 Responses leave one →
  1. 2017 May 28
    Pat Bower permalink

    I must have fertile soil since purslane grows all over our garden. How can we minimize growth?

  2. 2017 May 22
    Chandra Wong permalink

    This article is a great start to understanding weeds in the garden. Thanks!

  3. 2017 May 21
    Martin permalink

    What does an infestation of Fireweed (senecio Madagascarensis) mean? What’s missing? What does it like?

  4. 2017 May 21
    Reba Whisenhunt permalink

    What about Maypops or Passion Flower?

  5. 2017 May 19
    Laura permalink

    What about miners’ lettuce?

  6. 2017 May 18
    Terri permalink

    Pineapple weed (Matricaria discoidea), grows in hard, compacted soil too.

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