What Weeds Can Tell You About Your Garden
Soil Indicators and Enhancers
Dandelions and other weeds
• Read the weeds to determine soil conditions, then cultivate plants that grow well in that kind of soil. Where you find sorrel or plantain— weeds that grow in compacted, acidic soil— plant parsley, potatoes, berries or other acid-loving plants. Where chickweed or nettles thrive, the soil is likely high in nitrogen— good for lettuce, broccoli, cabbage and other brassicas.
• Weeds indicate the soil health — 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 dirt. If your weeds are healthy, you will likely grow good vegetables.
• Flowering weeds attract early pollinators. Dandelions and other early bloomers produce pollen which attracts beneficial insects like ladybugs and bees to the garden. In early spring, this is especially helpful for vegetable beds not yet in flower.
• Compost your weeds; they’ll add nutrients to your garden. Weeds can draw up the nutrients in which a particular soil is deficient. Deep taproots of dandelions, docks and thistles reach down into the subsoil and bring up minerals and moisture that have leached to levels shallow-rooted vegetable plants can’t access. When you compost these weeds, they release their accumulated minerals back into the soil.
• Weeds make good companions as long as they don’t crowd out your cultivated plants. Not only do they draw up minerals your soil needs, these wild plants have extensive root systems which, as they decay, leave channels for drainage, and help build humus in the ground. Deep-rooted weeds can be used as companions to revive eroded, compacted soil. Weeds also prevent erosion, especially on steep slopes.
Common South Coast BC Garden Weeds
(Click to enlarge photos)
Bindweed
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
Buttercup (Ranunculus)
Thrives in poorly drained, cultivated garden soil. Creeping buttercup accumulates potassium from the soil. Buttercup produces an toxin called protanemonin which may suppress growth of adjacent plants.
Chickweed
Chickweed (Stellaria)
When healthy, chickweed indicates tilled, fertile, nitrogen-rich 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
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
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
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
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
Thrives in heavy, compacted, acidic, low-fertility soil. Plantain is rich in calcium and magnesium. It also accumulates silicon, sulphur, manganese and iron. When turned under to decompose, it helps to de-acidify the soil.
Quack Grass
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
Grows in acidic, low lime soil. Sheep’s sorrel can bring up calcium and phosphorus, minerals that alkalinize the soil. Turning sorrel under makes these minerals available in the soil.
Thistle
Thistle is found in heavy, compacted soil. Its deep roots help break up the subsoil and bring up iron and moisture for use by shallow-rooted plants. Canada thistle roots can penetrate as deep as 6 meters (20 feet) into the soil.
Vetch
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
Common Weeds of Northern United States and Canada
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More about gardening:
10 Tips for Year-Round Vegetable Gardens
Three Simple Ways to Test Your Soil
Dandelion and cudweeds are a sign of potassium deficiencies too
Thanks for this useful consideration of weeds. For those that propagate by rhizome, etc, as well as seed – such as buttercup, morning glory, quack grass: how/when can we be sure they are devoid of life and safe to incorporate into the soil or compost?
I have seen buttercup survive weeks without light, turning albino as it spread under tarp in search of a better home.
And after pulling dandelions which had not opened flower, I left them to wilt in the sun. Three days later upon returning to the site I found the seeds had set!
Also, any soil indicators for Water Blinks miner’s lettuce? It took over a newly cultivated sloped field, previously sod.
Thanks kindly – Vancouver BC.
I would not recommend composting buttercup or quack grass in your garden. Instead, I like to maintain a compost area for invasive weeds (which I don’t use in the garden) in an unused corner, and just let the unwanted weeds decompose there.
Dandelions without their flowering heads (or about-to-flower heads) make good compost for the garden. The roots are especially beneficial.
Miner’s lettuce, a native plant, often grows in forests and wetlands, and is indicative of moist soil.
awesome article….I love to compost weeds and people never believe me how they benefit the soil so thanks for this article
My lawn is being crowded out by clover. The clover seems to be thriving while the grass is struggling. What should I do to turn that around? I want to be as chemical-free as possible. Thanks.
The clover is bringing nitrogen to your soil, so it’s an indicator of nitrogen-poor soil. In a garden, clover is often planted as a cover crop to improve the soil. You grow the clover and turn it under before it starts to flower. The roots decompose, enhancing the soil as they do. In a lawn, you could try something similar. Turn under the large areas of clover, and reseed with grass seed. In any case, it’s an indicator that you have nitrogen-poor soil.
I have weeds that have a woody root 2 to 4 inches under the surface of the soil that fans out many more white fragile roots. The weed in the garden and lawn has many spreading stems laying on the surface of the ground. Is successful I. Wood bark mulch, depleted lawn soil and composted garden soil. I have been hand digging and pulling the weeds for the city compost pickup. I don’t mind the continuous work but will paper mulch the gardens and cover with soil. It always seems to send out long roots to an open space even when heavily mulched. I will use organic fertilizer on the lawn and try overseeing in the fall and hope the grass eventually crowds it out. I stopped using chemical fertilizer several years ago and am trying to find best organic method to restore or replace lawn.
Woody roots that spread and send up stems are probably not weeds. More likely, they are the spreading roots of adjacent shrubs or trees.
There are a few more kinds in the lower mainland, but without uploading pictures I don’t even know their names. Great idea on the deduction of the soil condition :)
In our area of British Columbia we have three invasive weeds that are mostly very light green, almost white. I tilled raked planted and rolled an old messy piece of lawn and replanted with fresh seeds. Three weeks later grass was coming up fine, and then these pale leaves started coming up everywhere. They have a feathery root system and there are about 5 ormolu stems spreading out from each stock at ground level. Each stem curves up and out from ground, and the leaves are long narrow and soft and cupped. If left they try to totally smother the tiny grass shuts. Does any one recognize this invader?