A weed is a plant that merely grows out of place. So technically speaking, a rose bush could, by this definition, be a weed if not in a “proper” or useful place. Weeds can be a headache for those who strive to have a “perfect” garden, yet in reality, many weeds are the best source of food and medicine that’s available not just for us – but for our gardens as well. Even for us gardeners, weeds can be very helpful if we know a few basic principles.
What Weeds Can Do for the Soil
Weeds are true pioneers. They are opportunistic plants that take pride in taking root in disturbed areas or bare soils. 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.
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.
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. Alternatively, you can make a weed tea that even your houseplants can enjoy.
Weeds can tell you a lot about soil conditions. In fact, the use of weeds as soil indicators is not a new concept. In 50 AD, the great Roman scholar, Pliny the Elder observed that land supporting wild plum, elder, oak, and thimbleberry was also favourable for wheat production. Many North American immigrants chose land for their farms according to the vegetation it supported. They quickly recognized that white pine communities were characteristic of sandy soils of little agricultural value, whereas forests of birch, beech, maple, or hemlock indicated more fertile soils.
Signs of soil deficiencies:
- Bitterweed (Helenium tenuifolium), stinging nettle (Utica dioica), horsetail (Equisetum arvense) and wild buckwheat (Polygonum convolvulus) may all indicate a calcium deficiency in the soil.
- Burdock (Arctium lappa) indicates low calcium and manganese, high in iron, sulfate and potassium soils.
- Common (and mouse ear) chickweed (Cerastium fontanum) indicate very low calcium and phosphorus levels and very high potassium and sodium levels.
- Curly dock (Rumex crispus) loves compacted soil, low calcium and extremely high magnesium, and phosphorus.
- Knapweed (Centaurea maculosa) grows in soils that are low in calcium, and very low phosphorus levels.
- Lambsquarters (Chenopodium album) grows in low phosphorus, high potassium soils.
- Oxeye daisy (Chrysanthemum leucanthemum) prefers to grow in soils that are low phosphorus, high potassium and high magnesium soils.
- Redroot pigweed (Amaranthus retroflexus), are signs that the iron-manganese ratio is out of balance. It may indicate there is too much iron or too little manganese. It also indicates a soil that is very high in potassium and manganese and low in phosphorus and calcium.
Weeds and Your Soil Type
Acidic Soil Weeds (Low pH)
Alkaline Soil Weeds (High pH)
Neutral Soil Weeds
Dry Soil Weeds
Hard, Compacted Soil Weeds
Wet, Moist, Poorly-Drained Soil Weeds
Low Fertility Soil Weeds
The Dirt on Getting Healthy Soil
- Every teaspoon of soil is home to billions of microorganisms . . . bacteria, fungi, nematodes, insects, and earthworms that play important roles.
- Bacteria and fungi break down dead plant and animal tissue which become nutrients for plants.
- Nematodes eat plant material and other soil organisms, releasing plant nutrients in their waste.
- Specialized mycorrhizal fungi form symbiotic (mutually beneficial) relationships with plants. The fungi bring hard-to-reach nutrients and water directly to plant roots, and the plants provide the fungi with carbohydrates.
- Worms and insects shred and chew organic material into smaller bits bacteria and fungi can easily access.
- Garden earthworms burrow and create pathways in soil that fill with air and water for plant roots.
Attaining this healthy balance means you need to be adding organic matter to your soil (i.e. weed tea). Also, incorporate compost to compacted soil to increase air, water and nutrients for plants. Many experts will tell you to protect your topsoil with mulch or cover crops. However, be warned about your choice of mulch.
Not All Mulches are Safe
The source of most mulches are from treated wood such as used pallets, reclaimed wood from construction sites and from demolition sites. These woods can contain chromated copper arsenate, which is a form of arsenic as well as other chemicals including creosote.
Those decorative red and black-coloured mulches are mostly created from that old discarded wood. The reason these wood materials are used for coloured mulches is because they are very dry and readily absorb colouring agents. Fresh wood chips are not dyed as they do not readily absorb these dyes.
Dyed wood mulch does not break down to enrich the soil as a good mulch should. Instead, it leaches the possible contaminants into the soil harming or even killing beneficial soil bacteria, insects, and earthworms.
Wood mulches actually rob the soil of nitrogen by out-competing the plants for the nitrogen they need for their own growth. Dr. Harry Hoitnik, Professor Emeritus at Ohio State University warns that dyed mulches are especially deadly when used around young plants and in newer landscapes. These mulches may not be good for wildlife or for your pets.
For you gardeners don`t let weeds be a headache. Working with nature and not against it results in a win-win situation. Weeds are truly are your greatest ally in helping you attain and maintain a healthy garden, and when incorporated into your diet, a healthier you!
Chikishev, A. G. 1965. Plant indicators of soils, rocks, and subsurface waters. Consultants Bureau, NY.
Cocannouer, J. A. 1964. Weeds: Guardians of the Soil. DeVin-Adair, NY.