Archive for April, 2010

Weeds, ecology and health

This article was published in Chain Reaction #109 (The National Magazine of Friends of the Earth Australia)  July 2010.

What is a weed?  The generally accepted definition is that it is a plant out of place, but who dictates the right place for a plant to be?  The very idea of a weed is a cultural construction.  Nature knows no weeds.  The American poet Emerson wrote “a weed is a plant whose virtues have not yet been discovered.”

What is seen as a weed depends on the context – the location and the values of the person making the judgement – so that a plant that is considered to be out of place is different in a garden, an agricultural setting or a native forest.

The concept of weeds comes from the culture of domination of nature.  We feel the need to control our surroundings, and can’t stand for plants that can look after themselves, exhibitions of nature asserting itself in our man-made environments.

These plants can be useful to us in many ways, as food and medicine, and they have an essential role in repairing damaged landscapes and creating healthy ecosystems.  The fact that they grow freely, without any work being done by us, means that they cannot be exploited.  For this reason weeds are not valued, and even considered an enemy, in western cultures.

By getting to know our local wild plants and making use of them we can move away from the paradigm of subjugating nature for the purposes of economic growth, and towards a more harmonious and integrated relationship with our world.

a patch of tasty wild food in a supermarket carpark: includes purslane, amaranth, mallow and others

In times of scarcity, a knowledge of local weeds becomes essential to survival.  During the world wars, many people around the world became dependent on weeds for food and medicine.  When the Argentine economy collapsed in 2001, the government distributed pamphlets with information about edible weeds.

As we become familiar with the weeds growing in our neighbourhood and use them in our daily lives, we develop a closer relationship with nature.  We find ourselves becoming a part of the environment we live in, rather than imposing ourselves on top of it.  Value can be discovered in neglected landscapes, by exploring these spaces that are considered wastelands and recognising them as diverse ecosystems that are a source of abundance.  A wild food hunt is an adventure, which can be so much more fun than shopping.  By taking notice of what is happening around us, the changing seasons, and the patterns and cycles of nature, we can learn about the natural world through direct experience, using all our senses.  We come to understand that it is the land, not the supermarket, that feeds us.  By eating wild plants and animals we significantly reduce our ecological footprint – the amount of land that is cleared and farmed to provide for our needs.

Leafy greens contain almost all of the vitamins and minerals we need.  By eating foods that are more nutrient-dense, we reduce the overall quantity of food we need to eat, which means less effort for our body to assimilate, and less effort and cost involved in shopping, transporting and preparing our food.  In green vegetables, 90 per cent of vitamins are lost within hours of picking, so by eating directly from the living plant we can optimise our intake of nutrients.  All wild plants contain more nutrients than cultivated plants, as they have to spread their roots further to obtain water and reach fertile soil.

Obesity is caused by the body craving nutrients and feeling a need to eat more.  It is a symptom of malnutrition, rather than a lack of self-control.  Many people in western countries don’t have access to sufficient nutrients and suffer a range of health problems as a result.  Adding a few weeds to our diet could be enormously beneficial to our health.

Most weeds and leafy greens have some medicinal value.  The effects they are credited with vary between cultures and sources, and each individual experiences these effects differently.  Animals instinctively know which plants to eat when ill.  By getting to know the plants in our local area and tuning in to the way they affect our bodies, we may be able to regain these lost instincts and take responsibility for our own health.

Most leafy greens contain alkaloids – poisons that accumulate in the liver if eaten too often.  Different plants contain different alkaloids, so eating a variety provides a range of nutrients and prevents liver damage.  This same principle of varied eating, and everything in moderation, applies to all foods.

In the garden weeds have many benefits.  The weeds that grow in a particular place indicate the soil condition.  For example dock and sorrel can be found in poorly drained and acidic soils, salvation jane and horehound indicate overgrazed and compacted soil, caltrop and wireweed show that the soil is infertile and dry, and nettle, sow thistle and chickweed grow in rich, fertile loam.

As weeds are often deep-rooted, they bring nutrients to the surface that are not otherwise accessible to more shallow-rooted garden plants.  By cutting these deep-rooted plants and leaving them on the surface as mulch, the nutrients then feed surrounding plants.  The deep roots also aerate and add organic matter to compacted or poor soils, improving conditions for other plants.  Making compost or liquid fertiliser from weeds is another way to return these nutrients to the soil.

Weeds can form a living mulch, protecting the soil from the drying effects of sun and wind, and prevent leaching of soil nutrients.  Weeds can also contribute to pest management by providing an alternative target for pest species, and the flowers can attract predators that control pest insects.

Working with nature in the garden by observing and learning from wild plants, insects and animals that exist there can be enlightening, liberating and make gardening much more fun.

In degraded landscapes, weeds are essential in repairing the soil to create an environment where other plants can grow.  Weeds are a pioneer species, the first stage in the succession towards the healthy diverse ecosystem of a mature forest.  By colonising damaged land, weeds halt erosion, reduce salinity and add organic matter to the soil.  They protect other plants from sun, wind and predators.  As the plants that form the next stage in the succession grow, weeds are shaded out and the soil conditions become unsuitable, causing the weeds to die of their own accord.  Weeds such as blackberry, lantana, gorse and thistles are seen as an environmental problem but are actually nature’s way of redressing an imbalance.  They are part of the solution to underlying environmental damage.

Ecosystems change and evolve over time, as a result of changing climate, species migration and human impact.  Attempting to recreate the environments of 200 years ago is not necessarily a good thing, considering that humans have been altering the Australian environment for 40,000 years already.  Ecosystems of 200 years ago are no longer suitable to the conditions, and many introduced plants can be beneficial to our landscapes.

Some common edible weeds in southern Australia are dandelion, purslane, stinging nettle, fat hen, wild lettuce, mallow, chickweed and prickly pear.  When foraging for wild plants, there are a few points to consider.  Be sure to identify plants correctly, as similar looking plants may be poisonous.  Also be mindful of potential chemical contamination: railway corridors are often sprayed with herbicides, and runoff from busy highways may contain a range of contaminants.  Compared to the amount of chemicals applied to commercially grown fruit and vegetables, most weeds growing in urban and rural areas are unlikely to present a risk.  Be conscious of the amount you harvest in any location.  Leave enough behind for others to use, both human and non-human, and for the plants to grow and reproduce.

A plant will taste different depending on the conditions in which it grows.  The soil type, climate, season and plant genetics can affect taste and nutrient value.  Young leaves are much more palatable than older leaves, which become coarse and bitter.

Weeds can be added to salads, with the more bitter tasting leaves used only in small amounts so as not to be overpowering.  Weeds can also be cooked in the same way as any other leafy greens, in soups, omelettes or stir-fry dishes.  Green smoothies are an easy way to eat more leafy greens, by blending raw leaves with some fruit, for a tasty and nutritious breakfast.

References and resources

Australian Weeds – Gai Stern

How can I use herbs in my daily life? – Isabel Shippard

Growing Community: Starting and Nurturing Community Gardens – claire nettle

Beyond the Brink – Peter Andrews

Green for Life – Victoria Boutenko

Plants for a Future –

Article in The Age about edible weeds –

Radio interview with David Holmgren – A Permaculture Approach to Weeds