Weeds, Herbs, and More: Natural Living Pesticides For a Healthy Garden


 |  Food/Agriculture

With the various issues regarding environmental toxicity, contamination and mistreatment, there are solutions that are simple and harmless. These solutions are how nature intended to regulate itself, without requiring humanly-altered treatments to upkeep its own health. 

Plants that are considered weeds are those which were not intentionally grown, and can take up other plants’ space, but they are not unimportant. So although there is often a negative connotation attached to the term, weeds have much more to offer than meets the eye. 

Many plants which are considered weeds, can actually be used as pesticides, and indicators of soil and environmental health. Toxic chemicals, plant removal, and monoculture (or minimal ecological diversity), are methods used to increase yields which can directly kill insects and other critters such as racoons, rats, and possums, or getting rid or undesired, untargeted plants. However, this leads to unintended consequences, as these management strategies affect the plants which are then consumed resulting in a ripple effect of chemicals and lack of diversity, which leads to a less healthy ecosystem. 

So how can edible and non-edible gardens, residential and commercial landscapes, community gardens, and agricultural fields reduce the amount of damage caused by munching and egg-laying critters without actually harming them along with the wildlife populations? 

City garden in Prague Credit: C. Jon Bilous

How Do Plants Help Each Other?

Oftentimes, if plants grow in the same region, there is an ecological reason for why that proximity works. Plants can work together to help repel creatures that are considered pests, and plants that are considered weeds are actually supporting a symbiotic, connected system. When pairing plants, it is important to note that these plants should have similar needs (light, water, etc.) to be planted together.

Companion planting is a method of grouping plants together, which benefits all plants in the grouping. The benefits include nutrient maintenance, better pollination, and higher produce yields.  Some plants emit chemicals and scents which repel damage-causing insects and other animals. Contrarily, some also emit chemicals which attract insects who prey on the damaging insects, providing more biodiversity and balance in the area. By doing this, predatory insects, such as parasitic wasps, spiders, and mantids, save the plants. So companion planting can either simply repel certain insects, or, attract the ones who will get rid of the ones causing damage. 

Watermelon and marigolds Credit: Willowpix/Getty Images

Researchers have found that plants can shift their scent also, which adds another component to the defence process, making them more self-sufficient. 

The structure of plants is another component that makes them thrive when grouped together. For example, planting vining plants (i.e. beans) and stalk plants (i.e. corn) together so one can lean on the other for vertical support, as their growth habits complement each other. 

Here is a helpful source to get started with pairing plants. 

Parisian community garden combined with a colourful mural Credit: Madeleine D’Ersu

How Are ‘Weeds’ Important?

As mentioned in the previous section, plant structure plays a role in how well a plant will grow. In the case of weeds, they can often act as ground cover which prevents quick soil evaporation, and offer some protection to nearby plants from strong winds.

They are considered pioneers since these plants are resilient and are often the first plants to take over disrupted areas. Dandelions indicate that the soil is compact (they loosen it up with their roots), and is lacking in calcium. Weeds can indicate soil acidity based on their growing conditions, and release the minerals and nutrients that it needs to make a richer soil. Basically, they make the habitat more hospitable. Such as lamb’s quarters, the appearance of which indicates that the soil is fertile and rich in nitrogen. Or yarrow, which grows in sandy soil that isn’t very fertile and lacking in potassium. Many of these plants are actually edible and nutritious, considering they are not near roads or sprayed. 

Certain weeds send their roots so deep into the ground that they bring up nutrients through their root systems to distribute to crop plants. Even at the end of their life, these plants don’t stop providing nutrients. When they decompose they release nutrients into the soil and add organic matter. Food for other plants! And…

Food For Thought

A quote by Carl Sagan goes “ But down deep, at the molecular heart of life, the tree and we are essentially identical.” The seeming subtlety of these plants’ presence contrasted with their value and power, is a reminder that it is a big piece of the puzzle to let plants balance the Earth’s biochemistry. With a deeper understanding of the ecological systems around us, it becomes more evident how nature is a web of functions and creations, and how our actions can help regenerate the planet to thrive again.