What Weeds Can Tell Us About the Soil
Common Plants with Surprising Benefits

by nw farms and food  -  Permalink
June 28, 2010

Seeding dandelions and other weeds

Seeding dandelions and other weeds.

Recognize these weeds? If they’re growing in your garden, they may be trying to tell you something. Although we often regard weeds as troublesome interlopers, these wild plants, which love to root in areas of bare earth, offer many benefits to the garden. According to Louise Riotte, author of Carrots Love Tomatoes, a book about companion planting, weeds appear to “accumulate the nutrients in which a particular soil is deficient.” Deep taproots of such uninvited guests as dandelions and docks reach down into the subsoil to bring up minerals and moisture that have leached to levels that shallow-rooted vegetable plants can’t access. When these weeds are composted (preferably without their flowering heads), they release their accumulated minerals back into the soil.

Weeds often grow in bare areas where the soil is too poor to support other kinds of plants. In addition to concentrating minerals deficient in a particular soil into their structures, many wild plants have extensive root systems which, as they decay, leave channels for drainage, and help build humus in the ground. Some weeds can also absorb excess salt from the soil.


Weeds provide other benefits. Flowering weedsEnrich Your Soil With Weeds
produce pollen which attracts beneficial insects like ladybugs and bees to the garden. In early spring, this is especially helpful to vegetable beds not yet in flower. Weeds also prevent erosion, especially on steep slopes. Finally, weeds indicate the health of the soil—whether it is acidic, alkaline, compacted or fertile. By looking at the kinds of weeds in your garden, you can determine nutrient deficiencies and the general health of the earth. If you have healthy green weeds in your garden, you will likely grow good vegetables. And maybe this season you’ll add a few edibles like chickweed and dandelion greens along with your usual fare.

Common Northwest Garden Weeds

(Click to enlarge photos)

bindweed

Bindweed

Bindweed (Morning Glory) (Convolvulus)
The presence of bindweed indicates poor drainage, often hardpan soil with a crusty surface. Bindweed grows in neglected areas and does not like cultivated soil. The roots contain minerals which can be returned to the soil when composted.




Buttercup (Ranunculus)

Buttercup

Buttercup (Ranunculus)
Thrives in poorly drained, cultivated garden soil. Creeping buttercup accumulates potassium from the soil.






Chickweed (Stellaria)

Chickweed

Chickweed (Stellaria)
When healthy, chickweed indicates tilled, fertile soil. Chickweed often grows where the soil is cool and moist. Chickweed accumulates potassium, phosphorus and manganese which is released into the soil when it decomposes. Edible. Chickweed is sometimes used in salads. It is a source of vitamin C, B vitamins and minerals.



Clover (Trifolium)

Clover

Clover (Trifolium)
Indicates low fertility soil, low in nitrogen. Like other legumes, clover obtains nitrogen from the air and fixes it into the soil when tilled under. Clover can be planted as a cover crop.





Dandelion (Taraxacum)

Dandelion

Dandelion (Taraxacum)
Found in heavy, clay, compacted acidic soil, but also grows in fertile well-drained soil. The dandelion’s taproots bring up calcium, iron, and a host of other minerals from the deep soil. The decomposing roots of dandelions produce humus. Flowering dandelions provide early spring pollen that attracts ladybugs and other beneficial insects to the garden. Edible. Dandelion leaves are sometimes used in salads. They are rich in beta carotene, vitamin C and vitamin A.


Broadleaf Dock

Broadleaf Dock

Dock (Rumex)
Indicates waterlogged, poorly drained soils with increasing acidity. Docks have deep taproots that bring up calcium, potassium, phosphorus and iron, and help the soil structure.





Horsetail (Equisetum)

Horsetail

Horsetail (Equisetum)

Grows in low lime, sandy, light, acidic soil. Horsetail accumulates silicon, magnesium, calcium, iron and cobalt, which is released into the soil when it decomposes. Raising the pH and the fertility of the soil is the best way to eliminate horsetail from the garden.



Lanceleaf Plantain

Lanceleaf Plantain

Plantain (Plantago)
Thrives in heavy, compacted, acidic, low-fertility soil. Plantain is rich in calcium and magnesium. It also accumulates silicon, sulfur, manganese and iron. When turned under to decompose, it helps to deacidify the soil.




Quack grass

Quack grass

Quack Grass (Agropyron repens)
Grows in poorly drained, heavy clay soil or soil with a crusty surface. Quack grass has a net-like root system that can help control erosion on steep banks. It accumulates silicon, potassium and other minerals. Quack grass contains certain insecticidal properties that cause nerve damage to slugs. Some people use finely chopped quack grass as a mulch to repel slugs (with the caution that too much of the mulch could damage plantings).


Sorrel (Rumex)

Sorrel

Sorrel (Rumex)
Grows in acidic, low lime soil. Sheep sorrel can bring up calcium and phosphorus, minerals that alkalinize the soil. Turning sorrel under makes these minerals available in the soil.





Thistle

Thistle

Thistle
Thistle is found in heavy, compacted soil. It’s deep roots help break up the subsoil and bring up iron.






Vetch (Vicia)

Vetch

Vetch (Vicia)
Indicates low nitrogen, low fertility soil. A member of the legume family, vetch draws nitrogen from the air and fixes it in the soil as it decomposes. Vetches also accumulate potassium, phosphorus, copper and cobalt. Common vetch is sometimes used as a cover crop.




Resources on Weeds:

Weed Science Society of America Photo Gallery of Weeds

More Gardening Articles:
Saving Seeds, Sowing Food Security

Planning a Seed Saving Garden

16 Responses leave one →
  1. 2014 July 7
    Adam Haugeberg permalink

    Does anyone know what nutrients creeping charlie puts in the soil?

  2. 2014 June 19
    Barb permalink

    Some great info, BUT, I would NEVER encourage someone to attempt to compost Bindweed, aka Morning Glory. This plant, even a tiny part of it, is extremely hardy and can send taproots down 30 feet or more, and survive a LOT! The most effective way I’ve seen is to actually COVER the plant w. black tarp and rip out and toss EVERY part of the plant that pops out from under the tarp into the GARBAGE, not your mulch, not even commercial mulch. If you can’t do tarp, plant something else that outcompetes the morning glory like a fast growing tall grass, but, continue to pull and kill it by putting it in the garbage.

  3. 2014 June 18
    Eric permalink

    “A WEED IS ANY PLANT THAT YOU DO NOT LIKE”

    Elizabeth Howley
    Clackamas Community College (Horticulture)

  4. 2014 June 5
    Melissa permalink

    That is not Broadleaf Dock, that is Burdock.

  5. 2014 March 30
    Jayna Powell permalink

    We have Henbit growing in our front yard. Any suggestions, etc. on this weed. There is currently a hummingbird moth eating among them. :)

  6. 2013 June 3
    Tom Alexander permalink

    This is great information. Although there are a few information discrepancies on living conditions of some of these plants. Morning glory for instance. It does thrive in cultivated areas. We were constantly cultivating our grape vineyards and couldn’t get rid of it. It has a very deep rhizome. Take off the top and up comes another. And dandelions do not only prefer acid soils but love alkaline soils as well. I have a ton of them in my yard. And I live in a region where the soil is a sandy loam with a low alkaline base.

  7. 2013 June 3
    Phyl permalink

    Great article! I knew I had all these weeds, but I never understood WHY! Now I understand and can possibly do something about it!

  8. 2013 March 28
    diane permalink

    Hi
    Every year I fight a losing battle with creeping Charlie. I used to be able to pull it up with my hands, but that is no longer possible. I can ‘t use anything not organic on my lawn because of my dog. I heard cornmeal gluten could work, but the timing of this is important otherwise you just feed the weeds roots making the weed stronger.How much should I use? I live in low lying ground and get everyone’s rainwater.
    Thanks for your help
    Diane

    • 2013 May 15
      Sandi permalink

      Diane, I use 20 Mule Team Borax. You can google it and get the exact recipe for killing just the creeping charlie and not the rest of the lawn. I use it by sprinkling a line of it next to the paths that surround my garden, it kills the creeping charlie and keeps it from getting into my flower and vegetable beds. I haven’t tried to kill it in the lawn though. It lasts almost the whole season. Good luck!

      • 2013 May 15
        Sandi permalink

        I should have added, all plant need boron but too much kills them. Creeping charlie is especially sensitive to it.

  9. 2012 October 25
    Russell F permalink

    I remember many many years ago that Paul Harvey talking about weeds. He was telling that the weeds will reach down deep and bring up all the minerals to the surface. When I pull up weeds, I just recycle them into mulch.

  10. 2012 March 30
    Asad A. permalink

    Hi!
    I am a farmer and we are trying to go organic. How can we make a full plan, in the light of these guidelines, to have NPK and traces regulated without any external chemical/poison input.
    I shall be grateful if someone can leed me to such a resource on internet.

    • 2013 July 10
      andy hill permalink

      If you keep adding compost to the soil surface, and mulch well, including any weeds you pull up, you cannot go wrong.
      Bare soil loses water, nutrients, vitality. Ploughing or digging damages the symbiotic relationships in the soil.

    • 2014 June 16
      Karen N permalink

      Its called permaculture. Being organic as a descriptor of farming is very limiting and will often refer to no dig, mulching, composting and humus building as well as a commitment to using no chemicals.
      However what you want is the building of the farm ecosystems to work as a whole (there are Many ecosystems coexisting simultaneously and interconectively in the average garden)
      Knowing how to balance these to perpetuate health and virility in the garden IS permaculture. Organic is simply the basic ingredients of a permaculture system.
      Good news though, considering weeds and their place in ecosystems means you glean there is more to it than meets the eye. Also you must know the change is hard the first year but gives doubling returns every year there after. You will shortly wonder how farming could have been done any other way.
      A good page to read to help you on your way… http://en.m.wikipedia.org/wiki/Phytoremediation

      Phytoremediation (from Ancient Greek φυτο (phyto), meaning “plant”, and Latinremedium, meaning “restoring balance”) describes the treatment of environmental problems (bioremediation) through the use of plants that mitigate the environmental problem without the need to excavate the contaminant material and dispose of it elsewhere.

      This is common practise both commercially in mining reclaimation and in your case reclaiming land used in traditional farming to organic and restoring health. This might be step one in your permaculture plan… bioremedeation is used for wetlands, water resource reclamation if you understand that runoff of traditional farming damaged this resourse you’ll be needing healthy for your new direction

      These are only a few of the whole that is Permaculture. You want a plan, this will get you there and then some. Have animals? They are apart of your permaculture if you farm them too and will be folded in to your plan.

      Its a big subject, devote your study of it, tons of resources on the web infact degrees are given in its study.
      I hope this completely addresses your question. Good luck.

    • 2014 June 16
      Karen N permalink

      This sums it up nicely and gives great resources in the reference and external links section. A great primer.
      http://en.m.wikipedia.org/wiki/Permaculture

  11. 2010 October 12
    Kate Ashley permalink

    Very interesting.

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