What Weeds Can Tell You About Your Garden

Study the weeds in your garden and you may learn a lot about the soil. Although we’ve been trained to regard weeds as a nuisance, they actually offer many benefits to gardeners and farmers. Not only can they tell you about the condition of your soil, but they can also add nutrients, minerals and humus to the dirt, serve as companion plants, and attract pollinators to the garden when other flowers are not yet in bloom.

• 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 (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)

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 (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 (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)

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.

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)

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.

Plantain (Plantago)

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 (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)

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 (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
Common Weeds of Northern United States and Canada

 
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